(a) Washing soda crystals (b) Iron (III) chloride salts are exposed to the atmosphere. Answers: (a) Washing soda crystals loses few water molecules and forms its monohydrate. Reaction...
State your observation when
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Acids, Bases and Salts
Answer the questions below relating your answers only to salts in the following list: Sodium chloride, anhydrous calcium chloride, copper sulphate-5-water?
(a) What name is given to the water in the compound copper sulphate-5-water? (b) If copper sulphate-5-water is heated, anhydrous copper sulphate is formed. What is...
State the change noticed when blue litmus and red litmus are introduced in the following solutions:
(a) Na2CO3 solution (b) NaCl solution (c) NH4NO3 (d) MgCl2 Solution Answers: (a) Na2CO3 solution - Red litmus turns to blue (b) NaCl solution - No change in...
Name the salt which on hydrolysis forms
(a) Acidic (b) Basic and (c) Neutral solution. Give a balanced equation for each reaction. Answers: (a) Acidic - Iron chloride (FeCl3) Reaction Involved: FeCl3 + 3H2O → 3HCl...
(a) Why does common salt get wet during the rainy season?
(b) How can this impurity be removed? (c) Name a substance which changes the blue colour of copper sulphate crystals to white. (d) Name two crystalline substances which...
State whether a sample of each of the following would increase or decrease in mass if exposed to air.
(a) Solid NaOH (b) Solid CaCl2 (c) Solid Na2CO3.10H2O (d) Conc. sulphuric acid (e) Iron (III) chloride Answers: (a) Solid NaOH – Increases in mass when...
Give reasons for the following:
(a) Sodium hydrogen sulphate is not an acid, but it dissolves in water to give hydrogen ions according to the equation NaHSO4 ⇌ H+ + Na+ + SO42-...
Explain clearly how conc. H2SO4 is used as a dehydrating as well as a drying agent.
The concentrated Sulfuric acid (H2SO4) is hygroscopic in nature and can remove moisture from some substances, so it is used as a drying agent. Also, it can be used as a dehydration agent due to its...
Distinguish between drying and dehydrating agent.
Drying agentsDehydrating agentsRemoves moistureRemoves chemically joined elements of waterUsed to dry gases and used in desiccators to keep the substances dry.Prepares substances like...
(a) Define efflorescence. Give examples.
(b) Define deliquescence. Give examples. (a) Efflorescence is the property of a certain salt to completely lose, or partially their crystallization water when their crystals are exposed to dry air...
What do you understand by the water of crystallisation?
Give four substances which contain water of crystallisation and write their common names. Some salts, in turn, combine with a specific number of water molecules that enter a loose chemical reaction...
M is an element in the form of a powder. M burns in oxygen and the product obtained is soluble in water. The solution is tested with litmus. Write down only the word which will correctly complete each of the following sentences.
(i) If M is a metal, then the litmus will turn _____. (ii) If M is a non-metal, then the litmus will turn _____. (iii) If M is a reactive metal, then _____ will be evolved when M...
Salts are prepared by the following methods:
(a) Direct combination (b) Displacement (c) Double decomposition (precipitation) (d) Neutralisation of insoluble base (e) Neutralisation of an alkali (titration) Answers:...
Complete the following table:
ReactantsProductsMethodSoluble base + Acid (dil)Salt + waterNeutralisation TitrationMetal + Non-metalSalt (soluble/insoluble)……………Insoluble base +Salt (soluble) + water…………….Active metal + Acid...
Which of the following methods, A, B, C, D or E is generally used for preparing the chlorides listed below from (i) to (v). Answer by writing down the chloride and the letter pertaining to the corresponding method. Each letter is to be used only once.
A Action of an acid on a metal B Action of acid on an oxide or carbonate C Direct combination D Neutralisation of alkali by an acid E Precipitation (double decomposition) (i) Copper...
State the terms defined by the following sentences:
(a) A soluble base. (b) The insoluble solid formed when two solutions are mixed together. (c) An acidic solution in which there is only partial ionisation of the solute molecules. Answers:...
(a) Ca(H2PO4)2 is an example of a compound called _______ (acid salt/basic salt/normal salt).
(b) Write the balanced equation for the reaction of: A named acid and a named alkali. Answers: (a) Ca(H2PO4)2 is an example of a compound called acid salt. (b) Reaction Involved:...
From the formula listed below, choose one, in each case, corresponding to the salt having the given description: AgCl, CuCO3, CuSO4.5H2O, KNO3, NaCl, NaHSO4, Pb(NO3)2, ZnCO3, ZnSO4.7H2O.
(a) an acid salt (b) an insoluble chloride (c) on treating with concentrated sulphuric acid, this salt changes from blue to white (d) on heating, this salt changes from...
Choosing only substances from the list given in the box below, write equations for the reactions which you would use in the laboratory to obtain:
(a) Sodium sulphate (b) Copper sulphate (c) Iron(II) sulphate (d) Zinc carbonate Dilute sulphuric acidCopperCopper carbonateIronSodium...
For each of the salt: A, B, C and D, suggest a suitable method of its preparation.
(a) A is a sodium salt. (b) B is an insoluble salt. (c) C is a soluble salt of copper. (d) D is a soluble salt of zinc. Answers: (a) Preparation - Neutralisation Reaction...
You are provided with the following chemicals:
NaOH, Na2CO3, H2O, Zn(OH)2, CO2, HCl, Fe, H2SO4, Cl2, Zn Using suitable chemicals from the given list only, state briefly how you would prepare: (a) Iron(III) chloride, (b) Sodium sulphate, (c)...
Write the balanced equation for the preparation of the following salts in the laboratory:
(a) A soluble sulphate by the action of an acid on an insoluble base, (b) An insoluble salt by the action of an acid on another salt, (c) An insoluble base by the action of a soluble base...
Define the term neutralization.
(a) Give a reaction, mentioning clearly acid and base used in the reaction. (b) If one mole of a strong acid reacts with one mole of a strong base, the heat produced is always same. Why? Answers:...
(a) Give the pH value of pure water. Does it change if common salt is added to it?
(b) Classify the following solutions as acids, bases or salts. Ammonium hydroxide, barium chloride, sodium chloride, sodium hydroxide, H2SO4 and HNO3 (a) The pH of pure water is 7 and the pH does...
Give the preparation of the salt shown in the left column by matching with the methods given in the right column. Write a balanced equation for each preparation.
Zinc Sulphate Precipitation Ferrous sulphide Oxidation Barium Sulphate Displacement Ferric sulphate Neutralisation Sodium sulphate Synthesis Answers:...
Explain why:
(a) It is necessary to find out the ratio of reactants required in the preparation of sodium sulphate. (b) Fused calcium chloride is used in the preparation of FeCl3. (c) Anhydrous FeCl3 cannot...
What would you observe when:
(a) Blue litmus is introduced into a solution of hydrogen chloride gas. (b) Red litmus paper is introduced into a solution of ammonia in water (c) Red litmus paper is introduced in Caustic soda...
Fill in the blanks with suitable words:
An acid is a compound which when dissolved in water forms hydronium ions as the only …………… ions. A base is a compound which is soluble in water and contains …………….. ions. A base reacts with an acid...
Name:
(a) A chloride which is insoluble in cold water but dissolves in hot water, (b) A chloride which is insoluble, (c) Two sulphates which are insoluble, (d) A basic salt, (e) An acidic salt,...
The following is the list of methods for the preparation of salts.
A – Direct combination of two elements. B – a reaction of dilute acid with a metal. C – a reaction of dilute acid with an insoluble base. D – Titration of dilute acid with a solution of soluble...
Describe giving all practical details, how would you prepare:
(a) Copper sulphate crystals from a mixture of charcoal and black copper oxide, (b) Zinc sulphate crystals from Zinc dust (powered Zinc and Zinc oxide) (c) sodium hydrogen...
Answer the following questions related to salts and their preparations:
(a) What is salt? (b) What kind of salt is prepared by precipitation? (c) Name a salt prepared by the direct combination. Write an equation for the reaction that takes place in preparing the salt...
Define the following and give two examples in each case: (a) a normal salt, (b) an acid salt, (c) a mixed salt.
(a) Common salt: Normal salt is a salt formed by the complete replacement of hydrogen atoms with a metallic or ammonium ion. Eg: Na2SO4, NaCl (b) Acidic salts: Acid salts are formed by the...
Solution P has a pH of 13, solution Q has a pH of 6 and solution R has a pH of 2. Which solution
(a) will liberate ammonia from ammonium sulphate on heating? (b) is a strong acid? (c) contains molecules as well as ions? (a) Solution P will liberate ammonia from...
(a) A solution has a pH of 7. Explain how you would (i) increase its pH; (ii) decrease its pH
(b) If a solution changes the colour of litmus from red to blue, what can you say about its pH? (c) What can you say about the pH of a solution that liberates carbon dioxide from...
When you use universal indicator, you see that solutions of different acids produce different colours. Indeed, the solution of the same acid with different concentrations will also give different colours. Why?
The universal index is a pH index made of a mixture of dyes and several compounds that show many smooth color changes at different pH range, depending on the strength of the acid or base. By showing...
How does tooth enamel get damaged? What should be done to prevent it?
Things like chocolates and sweets are degraded by germs in our mouths. Tooth decay in humans begins when the pH falls below 5.5. Therefore, due to the low pH values, their tooth enamel which is the...
What should be added to
(a) Increase the pH value (b) Decrease the pH value of a neutral solution? (a) An alkali can be added to increase the pH value of a solution. (b) An acid can to be added to decrease...
Distinguish between:
(a) A common acid-base indicator and a universal indicator (b) The acidity of bases and basicity of acids (c) Acid and alkali (other than indicators) (a) A common acid-base indicator and a...
You are supplied with five solutions: A, B, C, D and E with pH values as follows:
A = 1.8, B = 7, C = 8.5, D = 13 and E = 5 Classify these solutions as neutral, slightly or strongly acidic and slightly or strongly alkaline. Which solution would be most likely to liberate hydrogen...
What do you understand by pH value? Two solutions X and Y have pH values of 4 and 10, respectively. Which one of these two will give a pink colour with a phenolphthalein indicator?
The strength of acids and alkalis is expressed in terms of hydrogen ion concentration which is represented as pH. The solution with pH value 10 is basic in nature so, it will give pink colour with...
Complete the table:
IndicatorNeutralAcidicAlkalineLitmus PhenolphthaleinPurple Colourless IndicatorNeutralAcidicAlkalineLitmus PhenolphthaleinPurple ColourlessBlue to red ColourlessRed to blue Pink
The skin has and needs natural oils. Why is it advisable to wear gloves while working with strong alkalis?
It is known that alkalis react with oil to form soap. Since our skin contains oil so when we touch strong alkalis, a reaction happens and a soapy solution is created. Therefore, it is recommended...
Write balanced equations to satisfy each statement.
(a) Acid + Active metal → Salt + Hydrogen (b) Acid + base → Salt + Water (c) Acid + Carbonate or bicarbonate → Salt + Water + carbon dioxide (d) Acid...
How would you obtain:
(a) A base from another base (b) An alkali from a base (c) Salt from another salt? (a) The base can be obtained from another base with double decomposition. The aqueous solution of salt at the base...
(a) Dry HCl gas does not change the colour of dry litmus paper. Why?
(b) ls PbO2 a base or not? Comment. (c) Do basic solutions also have H+(aq)? Explain why they are basic by taking an example? (a) Since dry HCl gas has no hydrogen ions in it compared...
HCl, HNO3, C2H5OH, C6H12O6 all contain H atoms but only HCl and HNO3 show acidic character. Why?
Since, HCl and HNO3 ionize in aqueous solution and produce hydrogen ions these reflect the acidic character. While ethanol and glucose does not ionize in an aqueous solution.
You have been provided with three test tubes. One of them contains distilled water and the other two have an acidic solution and a basic solution respectively. If you are given red litmus paper, how will you identify the contents of each test tube?
We know that the bases turn red litmus into blue. Therefore, when a drop is placed in each test tube on a red litmus paper that turns blue can easily be seen as a base. After that, the remaining...
Give one example in each case:
(a) A basic oxide which is soluble in water, (b) A hydroxide which is highly soluble in water, (c) A basic oxide which is insoluble in water, (d) A hydroxide which is insoluble in water, (e) A weak...
Name the ions furnished by:
(a) bases in solution, (b) an acid. (a) Hydroxyl ion (OH–) is furnished by basic solution. (b) Hydrogen ion (H+) is furnished by acidic solution.
What is the difference between:
(a) an alkali and a base, (b) the chemical nature of an aqueous solution of HCl and an aqueous solution of NH3. Answers: (a) AlkaliBaseSoluble in water Insoluble in waterAll alkalis are...
What do you understand by an alkali? Give two examples of: (a) Strong alkalis (b) Weak alkalis
Alkali is a basic hydroxide that when dissolved in water produces hydroxyl ions (OH–) as the only ion-charged ions. Examples: (a) Sodium hydroxide NaOH, Potassium hydroxide KOH (b) Calcium hydroxide...