(a) The circuit schematic below demonstrates how three resistors are connected. It is clear from the circuit above that 3 and 6 are linked in parallel. As a result, their comparable resistance is 2...
What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?
There is no voltage split among the electrical devices when they are linked in parallel. The supply voltage is equal to the potential difference between the devices. The effective resistance of the...
An electric lamp of 100 Ω, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?
A circuit diagram may be used to demonstrate the electric lamp, toaster, and water filter linked in parallel to a 220 V source: The resistors' equivalent resistance may be computed as follows:...
Judge the equivalent resistance when the following are connected in parallel – (a) 1 and , (b) 1 , , and .
The comparable resistance is provided by when 1 and \({{10}^{6}}\) ohms are linked in parallel. Thus, the equivalent resistance is 1 \(\ohm\) When 1 is linked in parallel with \({{10}^{3}}\) and...
Redraw the circuit of Question 1, putting in an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the 12 resistor. What would be the readings in the ammeter and the voltmeter?
To measure the potential difference, an ammeter should always be linked in series with resistors, while a voltmeter should be connected in parallel with the resistor, as illustrated in the diagram...
Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5 resistor, an 8 resistor, and a 12 resistor, and a plug key, all connected in series.
A battery with three 2 V cells equals a battery with a potential of 6 V. Three resistors with resistances of 12 ohms, 8 ohms, and 5 ohms are connected in series with a battery with a potential of 6...
Use the data in the table given below and answer the following questions.
a. Which among iron and mercury is a better conductor?
b. Which material is the best conductor?
a. Iron is a better conductor than mercury because mercury's resistivity is higher than that of iron. b. Silver is the best conductor of all the materials included in the table because its...
Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
Because of its high resistivity, an alloy's melting point is significantly greater than that of a pure metal. Alloys do not melt easily at high temperatures. As a result, alloys are found in heating...
Let the resistance of an electrical component remain constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?
Ohm's Law may be used to calculate the change in current passing through an electrical component. The current, according to Ohm's Law, is given by V/R = I The potential difference is now cut in half...
Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
The equation for resistance is: R=\(\rho \)I/A where, is the resistivity of the wire's substance, l is the wire's length. A is the cross-sectional area of the wire. The resistance is inversely...
On what factors does the resistance of a conductor depend?
The conductor's resistance is determined by the following factors: a. The conductor's temperature b. The conductor's cross-sectional area c. The conductor's length d. The conductor's material...
How much energy is given to each coulomb of charge passing through a 6 V battery?
We know that the equation gives us the potential difference between two locations. W/Q = V, where W denotes the amount of effort required to move the charge from one location to another. The charge...
What is meant by saying that the potential difference between two points is 1 V?
The potential difference between two points is 1 V when 1 J of effort is done to transfer a charge of 1 C from one point to another.
Name a device that helps to maintain a potential difference across a conductor.
One of the devices that helps to maintain a potential difference across a conductor is a battery, which consists of one or more electric cells.
Calculate the number of electrons constituting one coulomb of charge.
The charge of an electron is equal to \(1.6\times {{10}^{-19}}\) C. Using charge quantization as a guide, Q = nqe, where n denotes the number of electrons and qe denotes an electron's charge. The...
Define the unit of current.
The unit of current is ampere. Ampere is defined by the flow of one coulomb of charge per second.
What does an electric circuit mean?
An electric circuit is a continuous closed route made up of electric components through which an electric current travels. The following components make up a basic circuit: (a) Conductors (b)...
A person finds difficulty in seeing nearby objects clearly. His vision can be corrected by using spectacles containing:
a) converging lenses
b) diverging lenses
c) prismatic lenses
d) chromatic lenses
a) Converging lenses is the right answer.
A person cannot see distant objects clearly. His vision can be corrected by using the spectacles containing:
a) concave lenses
b) plane lenses
c) contact lenses
d) convex lenses
a) concave lenses is the right answer.
The defect of vision in which the eye-lens of a person gets progressively cloudy resulting in blurred vision is called:
a) myopia
b) presbyopia
c) colour blindness
d) cataract
d) cataract is the correct answer.
A man driving a car can read a distant road sign clearly but finds difficulty in reading the odometer on the dashboard of the car. Which of the following statement is correct about this man?
a) the near point of his eyes has receded away
b) the near point of his eyes has come closer to him
c) the far point of his eyes has receded away
d) the far point of his eyes has come closer to him
The correct answer is a) his eyes' near point has receded.
A student sitting on the last bench in the class cannot read the writing on the blackboard clearly but he can read the book lying on his desk clearly. Which of the following statement is correct about the student?
a) the near point of his eyes has receded away
b) the near point of his eyes has come closer to him
c) the far point of his eyes has receded away
d) the far point of his eyes has come closer to him
The correct answer is d) his eyes' distant point has moved closer to him
A person got his eyes tested. The optician’s prescription for the spectacles reads:
Left eye: -3.00D
Right eye: -3.50D
The person is having a defect of vision called:
a) presbyopia
b) myopia
c) astigmatism
d) hypermetropia
b) myopia is the proper answer.
After testing the eyes of a child, the optician has prescribed the following lenses for his spectacles:
Left eye: +2.00D
Right eye: +2.25D
The child is suffering from the defect of vision called:
a) short-sightedness
b) long-sightedness
c) cataract
d) presbyopia
Long-sightedness is the right answer.
A young man has to hold a book at arm’s length to be able to read it clearly. The defect of vision is:
a) astigmatism
b) myopia
c) presbyopia
d) hypermetropia
d) hypermetropia is the right answer.
Though a woman can see the distant objects clearly, she cannot see the nearby objects clearly. She is suffering from the defect of vision called:
a) long-sight
b) short-sight
c) hind-sight
d) mid-sight
a) long-sight is the right answer.
A person cannot see the distant objects clearly. He is suffering from the defect of vision called:
a) cataract
b) hypermetropia
c) myopia
d) presbyopia
c) myopia is the correct answer.
The defect of vision which cannot be corrected by using spectacles is:
a) myopia
b) presbyopia
c) cataract
d) hypermetropia
c) cataract is the correct answer.
The human eye can focus objects at focus objects at different distances by adjusting the focal length of the eye-lens. This is due to:
a) presbyopia
b) accommodation
c) near-sightedness
d) far-sightedness
Accommodation is the correct answer.
Compare and contrast fossil fuels and the sun as direct sources of energy.
Fossil fuels are derived from the remains of deceased plants and animals in the earth's crust. They are similar to coal and petroleum in that they are readily available. These are non-renewable...
Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the sun’s energy?
a. Geothermal energy
b. Wind energy
c. Nuclear energy
d. Bio-mass
c) Nuclear energy Nuclear fusion and nuclear fission are both sources of nuclear energy. Nuclear fission occurs when uranium atoms are attacked by low-energy neutrons, causing the atom to divide...
Which of the following is not an example of a bio-mass energy source?
a. Wood
b. Gobar-gas
c. Nuclear energy
d. Coal
c) Nuclear energy Dead plants and animal wastes are used to create bio-mass. There is a chemical change in these dead plants and animals as they mix with water and sunlight. Nuclear energy, on the...
A solar water heater cannot be used to get hot water on
a. A sunny day
b. A cloudy day
c. A hot day
d. A windy day
b) A cloudy day Solar energy is used to heat water in a solar water heater. On a cloudy day, the sunlight will be insufficiently powerful and dazzling, thus it will be reflected back into the sky by...
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
The following are the two non-renewable energy sources: Wood: Forests are the source of timber. The number of forests is decreasing as a result of deforestation. We all know that growing a forest...
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
The following are the two renewable energy sources: Wind: Wind energy is obtained from the air which is blowing at a high speed. Windmills capture wind energy and convert it to electricity. The...
(a) What is buckminsterfullerene? How is it related to diamond and graphite? (b) Why is diamond used for making cutting tools but graphite is not? (c) Why is graphite used for making dry cell electrodes but diamond is not?
Solution: (a) Buckminsterfullerene is a carbon allotrope with 60 carbon atom clusters linked together to create spherical molecules. Nothing is left behind when it burns to generate carbon dioxide...
(a) Give the general formula of an: (i) alkane, (ii) alkene and (iii) alkyne. (b) Classify the following compounds as alkanes, alkenes and alkynes: C2H4 , C3H4 , C4H8 , C5H12 , C5H8 , C3H8 , C6H6.
Solution: (a) (i) CnH2n+2 (ii) CnH2n (iii) CnH2n-2 (b) Alkanes: C5H12 , C5H8 Alkenes: C2H4 , C4H8 Alkynes: C3H4 ,C5H8
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Because CNG contains hydrocarbons, hydrogen gas is cleaner. CNG contains carbon, which is a pollutant. Hydrogen, on the other hand, is waste-free, and hydrogen fusion produces no waste. As a result,...
Can any source of energy be pollution-free? Why or why not?
There is no such thing as a pollution-free energy source. On the other hand, solar cells are considered pollution-free. However, their production may harm the ecosystem. There is no waste generated...
(a) What is meant by catenation? Name two elements that exhibit the property of catenation. (b) Write the names and structural formulae of all the possible isomers of hexane.
Solution: (a) Catenation is the property of carbon atoms self-combining to create a lengthy chain. Catenation is a characteristic that exists between carbon and silicon. (b) Hexane has five isomers:...
What are the advantages of nuclear energy?
The advantages of nuclear energy are as follows: Amount of energy produced per unit mass is large.It is clean because it does not produce pollutants.The energy produced by fissioning one atom of...
What is geothermal energy?
The energy obtained from the earth is referred to as geothermal energy. The energy comes from hot spots that form as molten materials at the earth's core are forced to the crust. In geothermal power...
What are the limitations of the energy that can be obtained from the ocean?
The following are some of the limitations of ocean energy: The tidal energy is affected by the relative positions of the earth, the sun, and the moon.High dams are required for converting tidal...
(a) What is the general name of all the compounds made up of carbon and hydrogen? (b) Why does carbon form compounds mainly by covalent bonding?
Solution: (a) Hydrocarbons are the broad term for all carbon and hydrogen-based molecules. (b) In order to reach the inert gas state by sharing electrons, carbon builds compounds primarily through...
What kind of mirror – concave, convex or plain would be best suited for use in a solar cooker? Why?
The heat source for a solar cooker is sunlight for both heating and cooking. The purpose of a mirror is to reflect and focus light at a single point. So, a concave mirror can be utilized in a solar...
(a) What is the atomic number of carbon. Write its electronic configuration. (b) What type of chemical bonds are formed by carbon? Why? (c) Name the three allotropic forms of carbon.
Solution: (a) Carbon has an atomic number of 6. It has a 2,4 electronic configuration. (b) Carbon can only acquire the inert gas electron configuration by sharing electrons, therefore it forms...
Fill in the following blanks with suitable words: (k) The IUPAC name of ethylene is ____. (l) The IUPAC name of acetylene is ____.
Solution: (k) Ethene (l) Ethyne Ethene and ethyne are chemical molecules that belong to the hydrocarbon family. Ethene is an alkene with two carbon atoms and four hydrogen atoms in its structure....
Fill in the following blanks with suitable words: (i) The property of carbon atoms to form long chains in compounds is called ______. (j) The general formula CnH2n for cycloalkanes is the same as that of ____.
Solution: (i) Catenation (j) Alkenes
Fill in the following blanks with suitable words: (g) Ethyne has _____ carbon-hydrogen single bonds. (h) Carbon compounds have usually _____ melting points and boiling points because they are ____ in nature.
Solution: (g) Two (h) Low; covalent
Fill in the following blanks with suitable words: (e) Hydrocarbons having the general formula CnH2n-2 are called _____. (f) Ethene and ethyne are examples of _____ hydrocarbons.
Solution: (e) Alkynes. An alkyne is an unsaturated hydrocarbon with at least one triple bond between carbon and carbon. With only one triple bond and no other functional groups, the simplest acyclic...
Fill in the following blanks with suitable words: (c) Compounds of carbon with hydrogen alone are called ____. (d) CnH2n is the general formula of ______ hydrocarbons.
Solution: (c) Hydrocarbons. A hydrocarbon is an organic molecule made completely of hydrogen and carbon in organic chemistry. Hydrocarbons are an example of hydrides in group 14. Hydrocarbons are...
Fill in the following blanks with suitable words: (a) The form of carbon which is known as black lead is ____. (b) The form of carbon that is used as a lubricant at high temperatures is ____.
Solution: (a) Graphite (b) Graphite Graphite, sometimes known as plumbago, is a crystalline form of the element carbon with atoms organised in a hexagonal pattern. It is the most stable form of...
Write down (i) structural formula, and (ii) electron-dot formula, of anyone isomer of hexane (C6 H14), other than n-hexane.
Solution: (i) Isomer of hexane: 2-methyl pentane.
How has the traditional use of wind and water energy been modified for our convenience?
Wind energy was captured earlier by employing windmills to accomplish mechanical activities like lifting or collecting water from a well. Windmills, on the other hand, are now used to generate...
What do you call the compounds having the same molecular formula but different structural arrangements of atoms?
Solution: Isomers are substances that have the same chemical formula but differ in other ways. Structural isomers are molecules that contain the same number and type of atoms but are bound to one...
Write the names of any two isomers represented by the molecular formula C5H12.
Solution: Isopentane and neopentane are the two isomers of C5H12.
Write the structural formula of butane.
Solution: Butane, sometimes known as n-butane, is a kind of alkane with the formula C4H10. At room temperature and atmospheric pressure, butane is a gas. Butane is a combustible, colourless, and...
Write the structural formula of propyne.
Solution: Propyne is a kind of alkyne having the formula CH3CCH. It's one of the ingredients in MAPD gas, along with its isomer propadiene, which was once widely utilised in gas welding. Propyne,...
Write the structural formula of propene.
Solution:
Give the IUPAC name of the following compound: C2H6
Solution: Ethane.
Write the electron-dot structures for: (i) ethane, (ii) ethene and (iii) ethyne.
Solution:
Give the name and structural formula of an alkyl group.
Solution: Methyl group: A methyl group is a methane-derived alkyl with one carbon atom linked to three hydrogen atoms — CH3. The group is frequently abbreviated Me in formulae. Many organic...
Name the hardest natural substance known.
Solution: Diamond. Each carbon atom has four electrons in its outermost shell. These electrons are shared with four other carbon atoms in diamond to form extraordinarily strong chemical bonds,...
Which of the following molecule is called buckminsterfullerene? C90 , C60 , C70 , C120
Solution: C60 is a molecule that consists of 60 carbon atoms, arranged as 12 pentagons and 20 hexagons. The name was chosen because the geodesic domes of Buckminster Fuller provided a clue that the...
How does graphite act as a lubricant?
Solution: Each carbon atom in graphite forms hexagonal rings with three other carbon atoms, which are held together by weak Vander Waal interactions to form layers. These layers can slide over one...
Name the black substance of pencil. Will the current flow through the electrical circuit when we use the sharpened ends of the pencil to complete the circuit?
Solution: Graphite is the black substance found within a pencil. Because graphite is a good conductor of electricity, the current will flow through the electrical circuit when we utilise the...
Buckminsterfullerene is a spherical molecule in which 60 carbon atoms are arranged in interlocking hexagonal and pentagonal rings of carbon atoms. (a) How many hexagons of carbon atoms are present in one molecule of buckminsterfullerene? (b) How many pentagons of carbon atoms are present in one molecule of buckminsterfullerene?
Solution: (a) One buckminsterfullerene molecule contains 20 hexagonal carbon rings. (b) One buckminsterfullerene molecule contains 12 pentagonal carbon rings.
In addition to some propane and ethane, LPG cylinders contain mainly two isomers of another alkane. Name the two isomers and write their condensed structural formula.
Solution: Apart from propane and butane 2 isomers found in LPG are- (i) n−butane: CH3-CH2-CH2-CH3 (ii) iso-butane: CH3-CH3-CH-CH3
Name the element whose allotropic form is graphite.
Solution: Carbon is the element whose allotropic form is graphite. Graphite is a crystalline form of carbon that is soft. Diamonds and fullerenes are two other types ("buckyballs"). It's opaque,...
Name the scientist who disproved the ‘vital force theory’ for the formation of organic compounds.
Solution: Friedrich Wohler is the scientist who debunked the 'vital force theory' for the production of organic molecules. Wöhler is well recognised for his contributions to organic chemistry,...
State whether the following statement is true or false: Diamond and graphite are the covalent compounds of carbon element (C).
Solution: True. Carbon's massive molecular structure is made up of covalently bound carbon lattices. Because these connections are extremely strong, they are rigid and have high melting points. A...
What are the two properties of carbon which lead to the formation of a large number of carbon compounds?
Solution: The following are two characteristics of carbon that give rise to a huge number of compounds: (i) Catenation refers to a carbon atom's ability to make bonds with other carbon atoms. (ii)...
Name the element whose one of the allotropic forms is buckminsterfullerene.
Solution: Carbon is an element with buckminsterfullerene as one of its allotropic forms. Diamond and graphite are the other allotropic forms of carbon.
Give two important uses of washing soda and baking soda.
Two uses of washing soda are as follows:- Used as an electrolyte.It can be used as a water softener for laundry in the home. Two uses of baking soda are as follows:- It can be used to determine the...
What is a neutralisation reaction? Give two examples.
The neutralisation reaction occurs when an acid and a base react to produce a product of salt and water. Examples:
Plaster of Paris should be stored in a moisture-proof container. Explain why?
Because moisture can harm the plaster of Paris by slowing the setting of the plaster due to hydration, it should be stored in a moisture-proof container. The plaster will be rendered worthless as a...
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline? (b) Why does this milk take a long time to set as curd? Answer: (a) To prevent the milk from becoming sour due to the...
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
The formation of lactic acid causes fresh milk to curdle. Curd contains lactic acid. Thus, due to the presence of an acid, the pH of milk is lowered.
Equal lengths of magnesium ribbons are taken in test tubes A and B.
Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. Amount and concentration taken for both the acids are the same. In which test tube will the...
Five solutions A, B, C, D, and E when tested with universal indicator showed pH as 4, 1, 11, 7, and 9, respectively.
Which solution is (a) neutral? (b) Strongly alkaline? (c) Strongly acidic? (d) Weakly acidic? (e) Weakly alkaline? Answer: In increasing order of hydrogen ion concentration: pH 11(C) < pH...
Zinc blende ore can be converted into zinc oxide by the process of (a) Roasting (b) Hydrogenation (c) Chlorination (d) Calcination
Solution: Option (a) is the answer. Zinc blende (also known as zinc sulphide or ZnS) is a zinc sulphide ore. Roasting (heating in the presence of air) converts sulphide ores to metal oxides. Zinc...
Why do acids not show acidic behaviour in the absence of water?
Acids have an acidic behaviour due to the presence of hydrogen ions. Because hydrogen ions can only be formed in the presence of water, water is required for acids to exhibit acidic behaviour.
Calamine ore can be converted into zinc oxide by the process of: (a) Dehydration (b) Roasting (c) Calcination (d) Sulphonation
Solution: Option (c) is the answer. Calamine is a zinc carbonate mineral (ZnCO3, zinc carbonate). Calcination (heating in the absence of air) converts carbonate ores to metal oxides. Calamine ore...
Why does distilled water not conduct electricity, whereas rainwater does?
Ionic compounds are not present in distilled water. Rainwater, on the other hand, contains far more chemicals.Carbonic acid is formed when rainwater dissolves acidic gases from the air, such as...
Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it
Two nails should be inserted into the wooden or rubber cork and placed on a beaker as shown in the illustration. Connect a bulb, a 6-volt battery, and a wire to the switch using an iron nail. Dip...
The metal which can be extracted from pyrolusite ore is: (a) Mercury (b) Manganese (c) Aluminium (d) Magnesium
Solution: Option (b) is the answer. Pyrolusite is a manganese ore that is primarily composed of manganese dioxide.It's a black, amorphous mineral with a granular, fibrous, or columnar structure that...
Sulphide ore is converted into metal oxide by the process of: (a) Carbonation (b) Roasting (c) Calcination (d) Anodising
Solution: Option (b) is the answer. Roasting is the term for this procedure. Heating sulphide ores in the presence of extra air converts them to oxides.
The articles made of silver metal become dark on prolonged exposure to air. This is due to the formation of a layer of its: (a) Oxide (b) Hydride (c) Sulphide (d) Carbonate
Solution: Option (c) is the answer. When silver reacts with hydrogen sulphide gas in the air, it forms a thick layer of silver sulphide (Ag2S). The creation of a silver sulphide coating on the...
Rock salt is an ore of one of the following metals. This metal is: (a) Mn (b) Na (c) Fe (d) Cu
Solution: Option b is the answer. Rock salt is a sodium chloride resource. The ore's compound is sodium chloride, which has the chemical formula NaCl.
Which of the following metals are extracted by the electrolysis of their molten chlorides? (a) Na and Hg (b) Hg and Mg (c) Na and Mg (d) Cu and Fe
Solution: Option (c) is the answer. Metals like sodium and magnesium are extremely reactive. They are obtained by electrolysis of their molten chlorides because they are difficult to reduce.
During galvanisation, iron metal is given a thin coating of one of the following metals. This metal is: (a) Chromium (b) Tin (c) Zinc (d) Copper
Solution: Option (c) is the answer. Galvanisation is the process of immersing iron items in molten zinc. This results in a thin zinc covering that shields the iron object against corrosion. Because...
The metal which can be extracted simply by heating the cinnabar ore in the air is: (a) Zn (b) Cu (c) Al (d) Hg
Solution: Option (d) is the answer. Because mercury is a less reactive metal, it can only be extracted from its cinnabar ore by heating it in the presence of air.
Manganese metal is extracted from manganese dioxide by a reduction process by making use of: (a) Carbon (b) Hydrogen (c) Electrolysis (d) Aluminium
Solution: Option (d) is the answer. Manganese metal is recovered from manganese dioxide using an aluminum-based reduction method.
Write word equations and then balanced equations for the reaction taking place when
(a) Dilute sulphuric acid reacts with aluminium powder. (b) Dilute hydrochloric acid reacts with iron filings. Answer: (a) Dilute sulphuric acid reacts with aluminium powder. dilute Sulphuric Acid +...
Write word equations and then balanced equations for the reaction taking place when
(a) Dilute sulphuric acid reacts with zinc granules. (b) Dilute hydrochloric acid reacts with magnesium ribbon. Answer: (a) Dilute sulphuric acid reacts with zinc granules: dilute sulphuric acid +...
The metal which is always present in an amalgam is: (a) Iron (b) Aluminium (c) Mercury (d) Magnesium
Solution: Option (c) is the answer. Mercury alloys are utilised as amalgams with metals such as silver, copper, tin and zinc.
Brass is an alloy of: (a) Cu and Sn (b) Cu and Pb (c) Pb and Sn (d) Zn and Cu
Solution: Option (d) is the answer. Brass is an alloy of copper and zinc. The proportion of copper and zinc can vary in quantities, resulting in brass with different mechanical and electrical...
Which one of the following types of medicines are used for treating indigestion? (a) Antibiotic (b) Analgesic (c) Antacid (d) Antiseptic
Indigestion is caused by the stomach producing too much acid. Antacids are medicines that are used to treat dyspepsia.
10 mL of a solution of NaOH is found to be completely neutralized by 8 mL of a given solution of HCl.
If we take 20 ml of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralize it will be (a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL Answer: Because 10 mL...
A solution reacts with crushed eggshells to give a gas that turns lime-water milky. The solution contains a) NaCl (b) HCl (c) LiCl (d) KCl
The answer is HCl. Calcium carbonate is found in eggshells, and when it reacts with HCl, it produces CO2, which turns lime water milky.
A solution turns red litmus blue, its pH is likely to be a) 1 (b) 4 (c) 5 (d) 10
Because litmus paper turns blue when it reacts with a basic solution, the answer is ten (p[H more than 7). As a result, the answer is 10.
Write an equation to show the reaction between Plaster of Paris and water.
The chemical equation for the reaction of Plaster of Paris and water is
What will happen if a solution of sodium hydrocarbonate is heated?
Give the equation of the reaction involved. Answer: When sodium hydrocarbonate is heated, sodium carbonate is formed, and carbon dioxide gas is released.
Name the sodium compound which is used for softening hard water.
The sodium compound that is utilised to soften hard water is sodium carbonate.
Name the substance which on treatment with chlorine yields bleaching powder
Calcium hydroxide is the material that produces bleaching powder when exposed to chlorine.
What is the common name of the compound CaOCl2?
The common name of CaOCl2 is bleaching powder.
Under what soil condition do you think a farmer would treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?
If the soil is acidic (pH below 7), quick lime (calcium oxide), slaked lime (calcium hydroxide), or chalk should be used to treat it (calcium carbonate).
Do basic solutions also have H+(aq) ions? If yes, then why are these basic?
Basic solutions contain H+ ions, although hydroxide ions are more prevalent in basic solutions. As a result, the presence of hydrogen ions causes the solution to become basic.
What effect does the concentration of H+(aq) ions have on the nature of the solution?
The nature of the solution is determined by the concentration of hydrogen ions. If the concentration of hydrogen ions in a solution increases, the solution becomes acidic; conversely, if the...
You have two solutions, A and B.
The pH of solution A is 6 and the pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of these is acidic and which one is basic? Answer: In order to find the hydrogen...
How is the concentration of hydroxide ions (OH–) affected when excess base is dissolved in a solution of sodium hydroxide?
When a base is dissolved in sodium hydroxide solution, the number of hydroxide ions increases, but it eventually reaches saturation. Even after adding more base after reaching saturation, the...
How is the concentration of hydronium ions (H3O+) affected when a solution of an acid is diluted?
When acid is introduced to water, a certain amount of hydronium ion will be present in a certain volume of solution. When we dilute a solution, the amount of hydronium ion per volume of solution...
While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
When diluting an acid, it is preferred that the acid be added to water rather than the water being added to the acid, because adding water to a concentrated acid releases a large amount of heat,...
Why does dry HCl gas not change the color of the dry litmus paper?
Because HCl does not emit hydrogen ions, it does not exhibit acidic behavior, and the color of the litmus paper does not change when it reacts with HCl gas.
Why does an aqueous solution of acid conduct electricity?
The conductivity of electricity in acid is caused by charged particles. The conductivity of electricity in acid is due to these charged particles known as ions.
Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
The presence of the H+ ion in water determines whether a substance is acidic or non-acidic. Acids are substances that produce hydrogen ions when they dissociate with water. As some chemicals...
Metal compound A reacts with dilute hydrochloric acid to produce effervescence.
The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride. Answer: The gas developed here is CO2 since the...
Which gas is usually liberated when an acid reacts with a metal?
Illustrate with an example. How will you test for the presence of this gas? Salt and hydrogen gas are generated when an acid combines with any metal. Metal + Acid → Salt + Hydrogen gas
Why should curd and sour substances not be kept in brass and copper vessels?
Acids are found in curd and sour foods, and these acidic chemicals react with metal. This reaction turns food into poison, putting people's health at risk.
You are given three test tubes.
The three test tubes contain distilled water, acidic solution, and the basic solution respectively. There is only red litmus paper available in order to identify what is there in each test tube. How...
Give reasons why copper is used to making hot water tanks and not steel (an alloy of iron).
Copper is used to make hot water tanks, rather than steel (an alloy of iron) because copper does not react with either water or steam, whereas iron reacts with steam to corrode the tank.
A man went door to door posing as a goldsmith.
He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new...
Differentiate between metal and non-metal on the basis of their chemical properties.
MetalsNon-metals1. When metals are heated with oxygen, ionic oxides occur, which are basic in nature and dissolve in water to produce bases. This changes the colour of red litmus paper to blue.1....
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice.
Explain why these sour substances are effective in cleaning the vessels. Answer: Lemon or tamarind is used to clean tarnished copper vessels because the sour ingredient includes acids that dissolve...
Give reasons
(a) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking. (b) Carbonate and sulphide ores are usually converted into oxides during the process of extraction Answer: (a)...
Give reasons
(a) Platinum, gold, and silver are used to make jewelry. (b) Sodium, potassium, and lithium are stored under oil. Answer: (a) Because platinum, gold, and silver are highly reactive metals, they are...
What type of oxides are formed when non-metals combine with oxygen?
When non-metals react with oxygen, acidic or neutral oxides are formed. CO is a neutral oxide, whereas N2O5 or N2O3 is an acidic oxide.
State two ways to prevent the rusting of iron.
Rust-proof paints can be applied to the surface of iron to keep it from rusting.Applying oil/grease to the surface of iron items prevents the iron surface from coming into touch with moisture-laden...
Pratyush took sulphur powder on a spatula and heated it.
He collected the gas evolved by inverting a test tube over it, as shown in figure below. (a) What will be the action of gas on (i) dry litmus paper? (ii) moist litmus paper? (b) Write a balanced...
In the electrolytic refining of a metal M, what would you take as the anode, the cathode, and the electrolyte?
An impure and thick block of metal M is used as anode in the electrolytic refining process, whereas a thin strip or wire of pure metal M is used as a cathode. The electrolyte is a metal M salt...
Name two metals that will displace hydrogen from dilute acids, and two metals which will not.
Due to their high reactivity, zinc (Zn) and magnesium (Mg) are the two metals that will displace hydrogen from dilute acids. Because gold (Au) and silver (Ag) are less reactive, they will not be...
What are amphoteric oxides? Give two examples of amphoteric oxides
Amphoteric oxides are oxides that react with both acids and bases to produce salt and water. PbO and Al2O3 are two examples. Amphoteric oxides are compounds that react with acids and bases to...
You are given a hammer, a battery, a bulb, wires, and a switch.
(a) How could you use them to distinguish between samples of metals and non-metals? (b) Assess the usefulness of these tests in distinguishing between metals and non-metals. Answer: (a) Metals are...
Food cans are coated with tin and not with zinc because
(a) Zinc is costlier than tin. (b) Zinc has a higher melting point than tin. (c) Zinc is more reactive than tin. (d) Zinc is less reactive than tin. Answer: The answer is c. Because zinc is more...
An element reacts with oxygen to give a compound with a high melting point.
This compound is also soluble in water. The element is likely to be (a) Calcium (b) Carbon (c) Silicon (d) Iron Answer: Correct answer is option (a) i.e Calcium. Calcium oxide is formed when calcium...
Which of the following methods is suitable for preventing an iron frying pan from rusting?
Applying greaseApplying paintApplying a coating of zincAll of the above Answer: Answer is (c) Applying a coat of Zinc Although adding grease and painting keeps iron from rusting, both methods cannot...
Which of the following pairs will give displacement reactions?
(a) NaCl solution and copper metal (b) MgCl2 solution and aluminium metal (c) FeSO4 solution and silver metal (d) AgNO3 solution and copper metal Answer: The right answer is option d,...
What are alloys?
A homogenous blend of two or more metals, or a metal and a non-metal, is known as an alloy.
Which metals do not corrode easily?
Metals that are unreactive or inert in nature do not tend to corrode easily. For example, gold and platinum. These metals are inert in nature and thus do not react and so can last longer than...
Metallic oxides of zinc, magnesium and copper were heated with the following metals.
Answer: A metal with a higher reactivity can displace a metal with a lower reactivity from its oxide. The displacement reaction will occur in the following cases: magnesium is the most reactive...
What chemical process is used for obtaining a metal from its oxide?
Metal is extracted from its oxide via the reduction technique. Heating with carbon, for example, reduces zinc oxide to metallic zinc. Example: When lead oxide is heated with carbon, it is reduced to...
Name two metals that are found in nature in the free state
The two metals found in nature in the Ffee state are gold and platinum.
Define the following terms:
(i) Mineral (ii) Ore (iii) Gangue Answer: (i) Minerals are natural chemicals (also known as elements) found in the earth's crust. For example Alums, K2SO4.Al2(SO4)3.24H2O, etc. (ii) Ores are...
Why do ionic compounds have high melting points?
The substances that have both positive and negative charges are referred to as ionic compounds. As a result, there will be a strong attraction between them. Because breaking this force of attraction...
Answer the following questions:
(i) Write the electron-dot structures for sodium and oxygen. (ii) Show the formation of Na2O and MgO by the transfer of electrons. (iii)What are the ions present in these compounds? Answer: (i)...
What would you observe when zinc is added to a solution of iron (II) sulphate?
Write the chemical reaction that takes place. Answer: Zinc is more electro-positive (reactive) than iron. As a result, Zinc takes the place of Iron in its salt solution. Ferrous sulphate has a pale...
Which gas is produced when dilute hydrochloric acid is added to a reactive metal?
Write the chemical reaction when iron reacts with dilute H2SO4. Answer: When dilute HCl is introduced to a reactive metal, hydrogen gas is produced.
Which of the following metals can be obtained from haematite ore? (a) Copper (b) Sodium (c) Zinc (d) Iron
Solution: Option (d) is the answer. Hematite: Iron is the metal recovered from the ore hematite.Hematite mineral has iron (III) oxide (Fe2O3). It is removed with aluminium.
Samples of four metals A, B, C, and D were taken and added to the following solution one by one.
The results obtained have been tabulated as follows Use the table above to answer the following questions about metals A, B, C and D. Which is the most reactive metal?What would you observe if B is...
During the refining of an impure metal by electrolysis, the pure metal is deposited: (a) At the cathode (b) On the walls of the electrolytic tank (c) At the anode (d) At the bottom of the electrolytic tank
Solution: Option (a) is the answer. The impure metal is deposited in the anode mud. But the pure metal is deposited on the cathode and anode mud contains contaminants.
Write equations for the reactions of
(i) iron with steam (ii) calcium and potassium with water Answer: (i) With the release of H2, iron reacts with steam to generate a magnetic oxide of Fe. (ii) Calcium forms calcium hydroxide and...
Which of the following alloys contains non-metal as one of the constituents? (a) Brass (b) Amalgam (c) Steel (d) Bronze
Solution: Option (c) is the answer. Steel is a metal and carbon-containing alloy steel (a non-metal).
Which of the following reactants are used to carry out the thermite reaction required for welding the broken railway tracks? (a) Al2O3 + Fe (b) MnO2 + Al (c) Fe2O3 + Al (d) Cu2O + Fe
Solution: Option (c) is the answer. Explanation: Iron oxide is reduced to iron by aluminium during the thermite process. This molten iron is then spilt on railways between the fractured iron to...
Calamine ore can be used to extract one of the following metals. This metal is: (a) Copper (b) Mercury (c) Aluminium (d) Zinc
Option (d) is the answer. Calamine: an astringent produced from zinc carbonate or zinc oxide, commonly used in the form of lotions for the treatment or pain of the skin or of bug bites.
Why is sodium kept immersed in kerosene oil?
Sodium is a reactive metal that, if left open, will react with oxygen and ignite. To avoid reactions with oxygen, moisture, and carbon dioxide in the air, sodium metal is immersed in kerosene.
Explain the meanings of malleable and ductile.
Malleable metals are those that can be pounded into sheets.Ductile metals are those that can be pulled into thin wires.
Which of the following pair of metals exist in their native state in nature? (a) Ag and Hg (b) Ag and Zn (c) Au and Hg (d) Au and Ag
Solution: Option (d) is the answer. The high-non-reactive metals are gold (Au) and silver (Ag.). Consequently, they can not react with oxygen or any other elements in the environment in their...
Give an example of a metal which
(i) Is the best conductor of heat? (ii) Is a poor conductor of heat? Answer: (i) Silver is the best heat conductor. (ii) Mercury and lead are both poor heat conductors.
Give an example of a metal which
(i) Is a liquid at room temperature? (ii) Can be easily cut with a knife? Answer: (i) Mercury is a liquid when kept at room temperature. (ii) The metals sodium and potassium may be sliced with a...
Which of the following is an ore of mercury metal? (a) Rock salt (b) Cinnabar (c) Calamine (d) Haematite
Solution: Option (b) is the answer. Cinnabar is a hazardous HgS-containing mercury sulphide mineral. It is mercury's sole significant ore. It has a shiny red colour, which for thousands of years in...
Which of the following alloys contains mercury as one of the constituents? (a) Stainless steel (b) Solder (c) Duralumin (d) Zinc amalgam
Solution: Option (d) is the answer. Explanation: Amalgam is understood to be an alloy containing mercury. Zinc amalgam is a liquid mercury and zinc alloy.
a) What is an electric motor? With the help of a labelled diagram, describe the working of a simple electric motor.
b) What are the special features of commercial electric motors?
Answer: a) An electric motor converts electrical energy into mechanical energy. Working: The coil ABCD is horizontal. The current enters the carbon brush P and the half ring X commutator. The coil...
a) State what would happen to the direction of rotation of a motor if:
i) the current were reversed
ii) the magnetic field were reversed
iii) both current and magnetic field were reversed simultaneously
b) In what ways can a motor be made more powerful?
Answer: a) i. As a result of reversing the current, the direction of rotation would be reversed. a) I If the current is reversed, the direction of rotation would be reversed. ii. It should be noted...
a) In a DC motor, why must the current to the coil be reversed twice during each rotation?
b) What device reverses the current?
Answer: a) The current to the coil in a DC motor must be reversed twice during each rotation because the coil will not rotate in the opposite direction until the current is reversed twice. b) A...
What is the principle of an electric motor? Name some of the devices in which electric motors are used.
Answer: The electric motor works on the Fleming left-hand rule. Hold the fingers, middle finger, and thumb of the left hand at right angles. The forefinger shows the magnetic field, the middle...
State Fleming’s left-hand rule. Explain it with the help of labelled diagrams.
Answer: Fleming's left hand rule states that the forefinger, the middle finger, and the thumb of the left hand should be held at right angles to one another. The direction of the force operating on...
a) A current-carrying conductor is placed perpendicularly in a magnetic field. Name the rule which can be used to find the direction of force acting on the conductor.
b) State two ways to increase the force on a current-carrying conductor in a magnetic field.
Answer: (a) The Fleming left-hand rule can be used to find the direction of force applied on a current-carrying conductor. (b) Increasing the current flow in a conductor in a magnetic field...
c) Name one device whose working depends on the force exerted on a current-carrying coil placed in a magnetic field.
Answer: (c) An electric motor works by applying force to a current-carrying coil in a magnetic field.
Fill in the following blanks with suitable words:
a) Fleming’s rule for the motor effect uses the ……
b) A motor contains a kind of switch called a …. Which reverses the current every half …..
Answer: (a) Fleming's Rule for the motor effect uses the left hand. Using Fleming's left-hand rule, the forefinger (or index finger) represents the magnetic field, the middle finger (or middle...
What is the role of the split ring in an electric motor?
Answer: An electric motor's split ring function is to reverse the direction of current flow through its coil whenever it moves from its horizontal position to its vertical position during the...
In an electric motor, which of the following remains fixed and which rotates with the coil?
Answer: The carbon brushes of the motor stay fastened to the motor's base, however, the commutator (divided rings) is free to revolve.
Of what substance is the core of the coil of an electric motor made?
Answer: The core of an electric motor's coil is comprised of soft iron, which gives it its flexibility. The soft iron used in the core of an electric motor's coil is used because it improves the...
Of what substance are the brushes of an electric motor made?
Answer: Carbon is used in the manufacture of electric motor brushes. It is through two brushes, which are often formed of carbon, that electricity is allowed to flow into the commutator and...
What is the function of a commutator in an electric motor?
Answer: The commutator in an electric motor has the function of reversing the direction of the current flow through the coil whenever the coil reaches the vertical position during the revolution of...
What is the other name of the split ring used in an electric motor?
Answer: The split ring used in an electric motor is also known as a commutator. In an electric motor, a split-ring or commutator has two conducting arcs separated by an insulator. It permits the...
Name the device which is used to reverse the direction of current in the coil of a motor.
Answer: Commutator A commutator is a device that reverses the direction of current in a motor's coil (or split ring). In an electric motor, a split ring or commutator has two conducting arcs...
For Fleming’s left-hand rule, write down the three things that are 90 to each other, and next to each one write down the finger or thumb that represents it.
Answer: a) current: the direction is indicated by the center finger b) Magnetic field: the forefinger indicates the direction of the magnetic field. c) Force or motion: the thumb indicates the...
State whether the following statement is true or false:
An electric motor converts mechanical energy into electrical energy.
Answer: False An electric motor converts electrical energy into mechanical energy.
A motor converts one form of energy into another. Name the two forms.
Answer: The two types of energy that are involved are as follows: a) Electricity as a source of energy b) Mechanical energy
Name the device which converts electrical energy into mechanical energy.
Answer: Electric motor is the device which converts electric energy into mechanical energy.
Name one device which works on the magnetic effect of current.
Answer: An electric bell is a gadget that operates on the magnetic field created by current flow. It is used to make sound by acting as an electromagnet.
In a statement of Fleming’s left-hand rule, what do the following represent?
a) direction of center finger
b) direction of the forefinger
c) direction of thumb
Answer: (a) According to Fleming's left-hand rule, the current is represented by the direction of the center finger. b) Fleming's left-hand rule expresses the magnetic field by the direction of the...
When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
Answer: When a current-carrying conductor is put in a magnetic field, the force experienced by the conductor is at its greatest when the conductor is at right angles to the magnetic field.
What happens when a current-carrying conductor is placed in a magnetic field?
Answer: An electrical current-carrying conductor is exposed to a magnetic field, which results in the conductor experiencing a mechanical force, which is responsible for its movement.
c) Explain why the core of an electromagnet should be of soft iron and not of steel.
d) State the factors on which the strength of an electromagnet depends. How does it depend on these factors?
Answer: c) Soft iron should be used as the core of an electromagnet rather than steel because soft iron loses its magnetism when there is no electric current flowing through it, whereas steel does...
a) What is an electromagnet? Describe the construction and working of an electromagnet with the help of a labelled diagram.
b) Explain why an electromagnet is called a temporary magnet.
Answer: a) The term "electromagnet" refers to a temporary magnet that operates when current is supplied through it. In order to construct an electromagnet, a soft iron is used with an insulated...
e) Write some of the important uses of electromagnets.
Answer: e) Electromagnets are used in a variety of electrical equipment, including loudspeakers, electric bells, and electric motors, among others. They are also used by doctors to cure their...
Long Answer Type Questions: c) What is the shape of field lines inside a current-carrying solenoid? What does the pattern of filed lines inside a current-carrying solenoid indicate?
d) List three ways in which the magnetic field strength of a current-carrying solenoid can be increased?
Answer: c) When the magnetic field lines inside a current-carrying solenoid are parallel to one another and in straight lines, the magnetic field inside the solenoid is uniform. d) When employing a...
Long Answer Type Questions: e) What type of core should be put inside a current-carrying solenoid to make an electromagnet?
Answer: e) A core of soft iron should be put inside a current-carrying solenoid to make an electromagnet.
Long Answer Type Questions: a) What is a solenoid? Draw a sketch to show the magnetic field pattern produced by a current-carrying solenoid.
b) Name the type of magnet with which the magnetic field pattern of a current-carrying solenoid resembles.
Answer: a) A solenoid is described as a lengthy coil of insulated copper wire that contains a large number of near turns and is used to operate a motor. b) It has been demonstrated that the magnetic...
a) How does an electromagnet differ from a permanent magnet?
b) Name two devices in which electromagnets are used and two devices where permanent magnets are used.
Answer: a) When compared to a permanent magnet, an electromagnet differs in that an electromagnet may produce a magnetic field as long as the current is running through it, whereas a permanent...
a) Draw a circuit diagram to show how a soft iron piece can be transformed into an electromagnet.
b) Describe how an electromagnet could be used to separate copper from iron in a scrapyard.
Answer: a. The circuit diagram is An insulated copper wire is twisted around coil C, with the ends of the copper wire being linked to a battery at either end of the coil. As a result, an...
Name any two factors on which the strength of magnetic field produced by a current-carrying solenoid depends. How does it depend on these factors?
Answer: The strength of a current-carrying solenoid's magnetic field relies on: a) the solenoid's strength is determined by its current. b) The number of turns of the solenoid determines the...
State and explain the clock face rule for determining the polarities of a circular wire carrying current.
Answer: The clock face rule states that looking at one face of a circular wire when current is flowing is: I) The round wire's face is the south pole when the current runs clockwise around it. ii)...
a) Draw the magnetic lines of force due to a circular wire carrying current.
b) What are the various ways in which the strength of the magnetic field produced by a current-carrying circular coil can be increased?
Answer: a) The diagram of the magnetic lines of force due to a circular wire carrying current. b) Enhance the number of turns of the wire in the coil and the current flowing through it to increase...
What is Maxwell’s corkscrew rule? For what purpose is it used?
Answer: As stated by Maxwell, the corkscrew represents current, while the handle represents magnetic field. This rule is used to find the magnetic field direction around a straight current-carrying...
State and explain Maxwell’s right hand thumb rule.
Answer: According to Maxwell's right-hand thumb rule, when a current-carrying conductor is held in the right hand, the thumb indicates the current direction and the fingers encircling the wire...
a) Draw a sketch to show the magnetic lines of force due to a current-carrying straight conductor.
b) Name and state the rule to determine the direction of magnetic field around a straight current-carrying conductor.
Answer: a) The diagram required: b) Maxwell's right hand rule is used to determine the magnetic field direction around a straight current-carrying wire. The thumb points in the direction of the...
Describe some experiment to show that the magnetic field is associated with an electric current.
Answer: As illustrated in the illustration, a thick insulated copper wire AB runs north-south. Under the copper wire AB is a plotting compass M. A switch connects both ends of the cable to the...
Describe how you will locate a current-carrying wire concealed in a wall.
Answer: A plotting compass can be used to locate a current-carrying wire hidden in a wall using the magnetic influence of the current. When the plotting compass is moved across the wall, the needle...