Class 12

### A …… lens is used to correct myopia and a ….. lens is used to correct hypermetropia. A Concave, concave B Convex, convex C Convex, concave D Concave, convex

Correct option is (D) Concave, convex Myopia means short-sightedness, in this, a person has a clear vision when looking at objects close to them, but distant objects will appear blurred, to correct...

### Rate of reaction of any substance depends on (A) active mass (B) molecular weight (C) atomic weight (D) equivalent weight

Correct option is (A) active mass The rate at which a substance reacts depends upon its active mass as the rate of reaction is directly proportional to concentration of each reactant and product.

### Formula of oleum is (A) (B) (C) (D)

Correct option is (A) $\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{7}$ Oleum, or fuming sulfuric acid, is a solution of various compositions of sulfur trioxide in sulfuric acid, or sometimes more...

### Two cells of emf and , internal resistance and , connected in parallel. The equivalent emf of the combination is- (A) (B) (C) (D)

Answer: Option (B)$\frac{\varepsilon_{1} r_{2}+\varepsilon_{2} r_{1}}{r_{1}+r_{2}}$

### Acetic acid on treatment with NaOH gives Y and with SOCl2 gives Z. Y and Z when heated form acetic anhydride. The compounds Y and Z respectively are:

Solution: Option 3 is correct Sodium hydroxide (NaOH) reacts with acetic acid (CH3​COOH) to form sodium acetate (CH3​COONa) and water  (H2​O). The equation for this reaction can...

### The standard enthalaphy of formation of ethane is -84.7 KJ/mol. What is the enthalapy change for the formation of 0.06 kg ethane?

1. -42.35 kJ 2. -169.4 kJ 3. -50.82 kJ 4. -236.7 kJ Solution: -169.4 kJ Given mass = 0.06 kg = 60 g Molar mass of ethane = 2(12) + 6(1) = 30 g number of moles of ethane in 60 grams = 60/30 = 2 We...

### What happens during the action of catalyst?

1. Temperature increases 2. Temperature decreases 3. Ea increases 4. Ea decreases Solution: Ea decreases A catalyst is a material that speeds up a reaction without being consumed in the process....

### The bisectors of angles A and B of a scalene triangle ABC meet at O. (i) What is the point O called? (ii) OR and OQ is drawn a perpendicular to AB and CA respectively. What is the relation between OR and OQ? (iii) What is the relation between ∠ACO and ∠BCO?

Solution: (i) The point O where the angle bisectors meet is called the incenter of the triangle. (ii) The perpendicular drawn from point O to AB and CA are equal. i.e., OR and OQ. (iii) ∠ACO = ∠BCO....

### Styrene and 1,3-butadiene on polymerisation forms

1. Buna-N 2. Neoprene 3. Butyl rubber 4. Buna-S Solution: Buna-S Styrene-butadiene rubber is another name for the rubber produced (SBR). Bu stands for butadiene, Na for sodium, and S for styrene in...

### Using ruler and compasses only, draw an equilateral triangle of side 5 cm and draw its inscribed circle. Measure the radius of the circle.

Solution: Steps to construct: Step 1: Draw a line segment BC = 5cm. Step 2: With Center as B and radius 5cm, with center as C and radius 5cm draw two arcs which intersect each other at point A. Step...

### Construct a tangent to a circle of radius 4cm from a point on the concentric circle of radius 6 cm and measure its length. Also, verify the measurement by actual calculation.

Solution: Steps to construct: Step 1: Mark a point O. Step 2: With center O and radius 4cm and 6cm, draw two concentric circles. Step 3: Join OA and mark its mid-point as M. Step 4: With center M...

### Two circles of radii 5 cm and 2-8 cm touch each other. Find the distance between their centers if they touch : (i) externally (ii) internally.

Solution: Radii of the circles are 5 cm and 2.8 cm. i.e. OP = 5 cm and CP = 2.8 cm. (i) When the circles touch externally, then the distance between their centers = OC = 5 + 2.8 = 7.8 cm. (ii) When...

### A point P is at a distance 13 cm from the center C of a circle and PT is a tangent to the given circle. If PT = 12 cm, find the radius of the circle.

Solution: CT is the radius CP = 13 cm and tangent PT = 12 cm CT is the radius and TP is the tangent CT is perpendicular TP Now in right angled triangle CPT, CP2 = CT2 + PT2 [using Pythagoras axiom]...

### Which among the following elements exhibits only +3 oxidation state?

Nd La Dy Yb Solution: La We have Z = 57 for La. In +3 oxidation state Lanthanum(La) achieves the noble gas configuration. So, Lanthanum exhibits only +3 oxidation state.

### (a) In the figure (i) given below, AB is a diameter of the circle. If ∠ADC = 120°, find ∠CAB. (b) In the figure (ii) given below, sides AB and DC of a cyclic quadrilateral ABCD are produced to meet at E, the sides AD and BC are produced to meet at F. If x : y : z = 3 : 4 : 5, find the values of x, y and z.

Solution: (a) Construction: Join BC, and AC then ABCD is a cyclic quadrilateral. Now in ∆DCF Ext. ∠2 = x + z and in ∆CBE Ext. ∠1 = x + y Adding (i) and (ii) x + y + x + z = ∠1 + ∠2 2 x + y + z =...

### (a) In the figure given below, PQ is a diameter. Chord SR is parallel to PQ.Given ∠PQR = 58°, calculate (i) ∠RPQ (ii) ∠STP (T is a point on the minor arc SP)

(b) In the figure given below, if ∠ACE = 43° and ∠CAF = 62°, find the values of a, b and c (2007) Solution: (a) In ∆PQR, ∠PRQ = 90° (Angle in a semi-circle) and ∠PQR = 58° ∠RPQ = 90° – ∠PQR = 90° –...

### Which is most stable oxidation state of Vanadium (Atomic no. 23)?

1. +2 2. +3 3. +4 4. +5 Solution: +5 Ammonium metavanadate, NH4VO3, is the most common source of vanadium in the +5 oxidation state. This isn't particularly water soluble, thus it's normally...

### When aniline forms 2,4,6- tribromo aniline on reaction with bromine water , it undergoes

1. nucleophilic addition 2. nucleophilic substitution 3. electrophilic substitution 4. electrophilic addition Solution: electrophilic substitution Bromination is the reaction that is taking place...

### For the elementary reaction . Identify the correct relation from the following relations:

Solution: the correct option is A As the reaction progresses, the reactant concentration decreases and the product concentration rises. As a result, the rate of...

### The decreasing order of thermal stability of hydrides of group 15 elements is

Solution: The correct option is 2. Hydride stability reduces as one moves along the group from NH3 to SbH3. This is because their bond dissociation enthalpy has decreased. The...

### The magnitude of is

1. Nature of solute only 2. Nature of the solute and the concentration of solution 3. Nature of the solvent and the concentration of solution 4. Nature of solvent only Solution: 3. Nature of the...

### What is SI unit of Luminous intensity?

1. Ampere 2. 0C 3. Kelvin 4. Candela Solution: Candela The SI unit of luminous intensity is candela.

### Two moles of an ideal gas are expanded from volume of 15.5 litre to 20 litre against a constant external pressure of 1 atmosphere. The amount of work done is

- 4.5 J 2×10-2 J - 506.5 J 225 J Solution: - 506.5 J The following equation can be used to describe the work done by a system against an external pressure: We know that: w =  -P​​ext ∆V 1atm...

### Which of the following is the strongest reducing agent?

Na Mg Li Ca Solution: Li Lithium has the highest ionization potential of all alkali metals, implying that its tendency to ionize to give Li+ ions should be the least, implying that Li should be the...

### Which among the following electrical properties has SI unit siemens per meter?

Conductance Conductivity Resistance Resistivity Solution: Conductivity The ability of an electrolyte solution to conduct electricity is measured by its conductivity (or specific conductance)....

### Aniline reacts with bromine water at room temperature to give

3-Bromoaniline 2-Bromoaniline 4-Bromoaniline 2,4,6-Tribromoaniline Solution: 2,4,6-Tribromoaniline       This happens due to the highly activating nature of -...

### Which of the following statements is not true for glyceraldehyde?

It is a sugar molecule It is optically active It contains two asymmetric carbon atoms It has carbonyl and hydroxyl group Solution: It contains two asymmetric carbon atoms        ...

### Copper crystallizes as face centered cubic lattice , with edge length of unit cell 361 pm. Calculate the radius of the copper atom.

108.6 pm 127.65 pm 181.6 pm 157.6 pm Solution: 127.65 pm For F.C.C,  a√2 = 4r 361×√2 = 4r r = 127.65 pm

### What is the bond length of C-H bonds in alkanes?

154 pm 120 pm 133pm 112pm Solution: 112 pm

### Which of the following solution will have highest freezing point depression?

M Glucose M Sucrose M Urea M KCl Solution: M KCl ΔTf = i Kf m ΔTf is the freezing point depression, i is the van’t Hoff factor, Kf is the molal freezing point depression constant for the solvent,...

### Identify the polymer from following, that contains amide linkage

Terylene PHBV Nylon - 6,6 Dextron Solution: Nylon-6,6 Polyamides have the amide linkage. Example- Nylon 6-6, Nylon 6 Nylon 6, 6 is used in the manufacturing of sheets, brush bristles, and...

### The volume of 400cm3 of chlorine gas at 400 mm of Hg is decreased to 200 cm3 at constant temperature. What is new pressure of the gas?

800 mm of Hg 1600 mm of Hg 200 mm of Hg 600 mm of Hg Solution: 800 mm of Hg This is an example of Boyle's law, which states that the volume of a gas is inversely proportional to the pressure at...

### What is the melting point of zinc?

473 K 1193 K 423 K 692 K Solution: 692 K The metal Zinc has a melting point of 692K.

### Which among the following polymers is an example of addition polymers?

Dacron Unrealformaldehyde Polymer Nylon-6 Polythene Solution: Polythene The addition polymers are formed by the repeated addition of monomer molecules possessing double or triple bonds, e.g., the...

### Which among the following is a first oxidation product of butan-2-ol?

Butanal Butanoic Acid Propanoic acid and carbon di-oxide Butan-2-one Solution: Butan-2-one Ketone is the first oxidation product of secondary alcohol. For example, butan-2-ol is oxidised to...

### Which of the following compounds is obtained when benzene is treated with CO and HCl in presence of catalyst anhyfrous under high pressure?

Toulene Benzoic Acid Benzaldehyde Acetophenone Solution: Benzaldehyde       When the vapors of CO and HCI are passed into benzene in the presence of anhydrous AICI3/CuCI, benzaldehyde...

### Which among the following oxides of nitrogen, the nitrogen atom contains one unpaired electron?

$A)\,{{N}_{2}}{{O}_{4}}$ $B)\,N{{O}_{2}}$ $C)\,{{N}_{2}}{{O}_{5}}$ $D)\,{{N}_{2}}{{O}_{3}}$ Solution:  $B)\,N{{O}_{2}}$ Among the oxides of nitrogen, only NO2​ contains odd number of...

### Calculate the wavelength of an electron moving with a velocity of

As per de Broglie’s equation, $\lambda=\frac{h}{m v}$ Where, $\lambda$ denotes thr wavelength of the moving particle $\mathrm{m}$ is the mass of the particle $v$ denotes the velocity of the...

### Glycogen is a branched-chain polymer of α-D-glucose units in which chain is formed by C1—C4 glycosidic linkage whereas branching occurs by the formation of C1-C6 glycosidic linkage. Structure of glycogen is similar to __________. (i) Amylose (ii) Amylopectin (iii) Cellulose (iv) Glucose

Option (ii) is the answer. Glycogen has a similar structure to amylopeptin. It's an a-D glucose unit branched chain polymer with C1-C4 glycosidic linkage for chain formation and C1-C6 glycosidic...

### Which of the following polymer is stored in the liver of animals? (i) Amylose (ii) Cellulose (iii) Amylopectin (iv) Glycogen

Option (iv) is the answer. Glycogen is a type of sugar that is stored in the liver of mammals.

### Sucrose (cane sugar) is a disaccharide. One molecule of sucrose on hydrolysis gives _________. (i) 2 molecules of glucose (ii) 2 molecules of glucose + 1 molecule of fructose (iii) 1 molecule of glucose + 1 molecule of fructose (iv) 2 molecules of fructose

Option (iii) is the answer. Cane sugar (sucrose) is a disaccharide. When sucrose is hydrolyzed, one molecule of glucose and one molecule of fructose are produced.

### Which of the following pairs represents anomers?

Option (C) is the answer. Anomers are isomers that differ only in the conformation of the hydroxyl group at C—1 and are known as - and -fonns.

### Proteins are found to have two different types of secondary structures viz. α-helix and β-pleated sheet structure. α-helix structure of the protein is stabilised by : (i) Peptide bonds (ii) van der Waals forces (iii) Hydrogen bonds (iv) Dipole-dipole interactions

Option ( iii) is the answer. Hydrogen bonding help to keep the -helix structure of proteins stable. By twisting into a right-handed helix and hydrogen bonding the -NH group of each amino acid...

### In disaccharides, if the reducing groups of monosaccharides i.e. aldehydic or ketonic groups are bonded, these are non-reducing sugars. Which of the following disaccharide is a non-reducing sugar?

Option (B) is the answer. This structure represents sucrose, in which the C1—C2 glycosidic bond connects -D glucose and -D-fructose. This is a non-reducing sugar since the reducing groups of glucose...

### Which of the following acids is a vitamin? (i) Aspartic acid (ii) Ascorbic acid (iii) Adipic acid (iv) Saccharic acid

Option (ii) is the answer. Vitamin C is ascorbic acid. Amino acid aspartic acid is a kind of amino acid. Dicarboxylic acids include adipic acid and saccharic acid.

### Dinucleotide is obtained by joining two nucleotides together by phosphodiester linkage. Between which carbon atoms of pentose sugars of nucleotides are Are these linkages present? (i) 5′ and 3′ (ii) 1′ and 5′ (iii) 5′ and 5′ (iv) 3′ and 3′

Option (i) is the answer. Between the pentose sugars of nucleotides, there are 5′ and 3′ connections.

### Nucleic acids are the polymers of ______________. (i) Nucleosides (ii) Nucleotides (iii) Bases (iv) Sugars

Option (ii) is the answer. Nucleic acids are nucleotide polymers connected together by phosphodiester linkage.

### Which of the following statements is not true about glucose? (i) It is an aldohexose. (ii) On heating with HI, it forms n-hexane. (iii) It is present in furanose form. (iv) It does not give 2,4-DNP test.

Option (iii) is the answer. It's found in the pyranose structure.

### Each polypeptide is a protein has amino acids linked with each other in a specific sequence. This sequence of amino acids is said to be ____________. (i) primary structure of proteins. (ii) secondary structure of proteins. (iii) the tertiary structure of proteins. (iv) quaternary structure of proteins.

Option (i) is the answer. The main structure of proteins is the sequence of amino acids in a polypeptide chain.

### DNA and RNA contain four bases each. Which of the following bases is not present in RNA? (i) Adenine (ii) Uracil (iii) Thymine (iv) Cytosine

Option (iii) is the answer. Adenine, guanine, thymine, and cytosine are the four bases found in DNA. Adenine, uracil, guanine, and cytosine are the four bases found in RNA. As a result, thymine is...

### Which of the following B group vitamins can be stored in our body? (i) Vitamin B1 (ii) Vitamin B2 (iii) Vitamin B6 (iv) Vitamin B12

Option (iv) is the answer. Because vitamin B12 is water insoluble, it can be stored in the body.

### Which of the following bases is not present in DNA? (i) Adenine (ii) Thymine (iii) Cytosine (iv) Uracil

Option (iv) is the answer. In DNA, uracil is absent; instead, thymine is present.

### Three cyclic structures of monosaccharides are given below which of these are anomers.(i) I and II (ii) II and III (iii) I and III (iv) III is anomer of I and II

Option (i) is the answer. Anomers are cyclic configurations of monosaccharides that differ in structure at carbon-1. I and II are anomers in this case because they differ solely in carbon-1.

### Which of the following reactions of glucose can be explained only by its cyclic structure? (i) Glucose forms pentaacetate. (ii) Glucose reacts with hydroxylamine to form an oxime. (iii) Pentaacetate of glucose does not react with hydroxylamine. (iv) Glucose is oxidised by nitric acid to gluconic acid

Option (iii) is the answer. The absence of a free -CHO group is indicated by the fact that glucose pentaacetate does not react with hydroxylamine. Only the cyclic nature of glucose may explain this...

### Optical rotations of some compounds along with their structures are given below which of them have D configuration.(i) I, II, III(ii) II, III(iii) I, II(iv) III

Option (i) is the answer. The -OH group is on the lowest asymmetric carbon on the right side of the I, II, and III structures, which is similar to (+) glyceraldehyde.

### Structure of a disaccharide formed by glucose and fructose is given below. Identify anomeric carbon atoms in monosaccharide units.(i) ‘a’ carbon of glucose and ‘a’ carbon of fructose. (ii) ‘a’ carbon of glucose and ‘e’ carbon of fructose. (iii) ‘a’ carbon of glucose and ‘b’ carbon of fructose. (iv) ‘f’ carbon of glucose and ‘f ’ carbon of fructose.

Option (iii) is the answer. Anomeric carbon is carbon that is next to an oxygen atom in the cyclic structure of glucose or fructose. 'a' and 'b' are next to the oxygen atom, as illustrated in the...

### Three structures are given below in which two glucose units are linked. Which of these linkages between glucose, units are between C1 and C4 and which linkages are between C1 and C6?(i) (A) is between C1 and C4, (B) and (C) is between C1 and C6 (ii) (A) and (B) are between C1 and C4, (C) is between C1 and C6 (iii) (A) and (C) is between C1 and C4, (B) is between C1 and C6 (iv) (A) and (C) is between C1 and C6, (B) is between C1 and C4

Option (iii) is the answer (A) and (C) are in the Cl-C4 range, while (B) is in the Cl-C6 range.

### Carbohydrates are classified on the basis of their behaviour on hydrolysis and also as reducing or non-reducing sugar. Sucrose is a __________. (i) monosaccharide (ii) disaccharide (iii) reducing sugar (iv) non-reducing sugar

Option (ii) and (iv) are the answers. Sucrose is a non-reducing sugar and a disaccharide.

### Proteins can be classified into two types on the basis of their molecular shape i.e., fibrous proteins and globular proteins. Examples of globular proteins are : (i) Insulin (ii) Keratin (iii) Albumin (iv) Myosin

Option (i) and (iii) are the answers Globulular protein is the structure that develops when a chain of polypeptides coils around to form a spherical shape. Insulin and albumin, for example, are...

### Which of the following carbohydrates are branched polymer of glucose? (i) Amylose (ii) Amylopectin (iii) Cellulose (iv) Glycogen

Option (i) and (iv) are the answers. Amylopectin and glycogen are both glucose branching polymers.

### Amino acids are classified as acidic, basic or neutral depending upon the relative number of amino and carboxyl groups in their molecule. Which of the following is acidic?

Option (ii) and (iv) are the answers. Acidic amino acids have more than one -COOH group one against the –NH2 group.

### Lysine, is _______________.(i) α-Amino acid (ii) Basic amino acid (iii) Amino acid synthesised in the body (iv) β-Amino acid

Option (i), (ii) and (iii) are the answers. (a)Lysine is a kind of amino acid with the structural formula . (b) Because the number of NH2 groups (2) is more than the number of COOH groups, it is a...

### Which of the following monosaccharides are present as five-membered cyclic structure (furanose structure)? (i) Ribose (ii) Glucose (iii) Fructose (iv) Galactose

Option (i) and (iii) are the answers. The five-membered cyclic structure of ribose and fructose is shown (furanose structures). They have a five-membered ring, similar to the foran compound....

### In fibrous proteins, polypeptide chains are held together by ___________. (i) van der Waals forces (ii) disulphide linkage (iii) electrostatic forces of attraction (iv) hydrogen bonds

Option (ii) and (iv) are the answers. Disulphide linkage and hydrogen bonding hold polypeptide chains together in fibrous proteins.

### Which of the following are purine bases? (i) Guanine (ii) Adenine (iii) Thymine (iv) Uracil

Option (i) and (ii) are the answers. Purines are made up of a six-membered nitrogen-containing ring fused together with a five-membered nitrogen-containing ring. Purine bases guanine and adenine...

### Which of the following terms are correct about enzyme? (i) Proteins (ii) Dinucleotides (iii) Nucleic acids (iv) Biocatalysts

Option (i) and (iv) are the answers. Enzymes are protein molecules that act as biocatalysts in the body's chemical reactions.

### Name the sugar present in milk. How many monosaccharide units are present in it? What are such oligosaccharides called?

Lactose is the sugar found in milk. Glucose and galactose are two monosaccharides found in lactose. Disaccharides are oligosaccharides that include two monosaccharide units.

### How do you explain the presence of all the six carbon atoms in glucose in a straight chain?

When glucose is heated with HI for a long time, n-hexane develops, implying that all six carbon atoms are connected in a straight chain.

### In nucleoside, a base is attached at 1C position of the sugar moiety. A nucleotide is formed by linking the phosphoric acid unit to the sugar unit of a nucleoside. At which position of sugar unit is the phosphoric acid linked in a nucleoside to give a nucleotide?

When a nitrogenous base is connected to the 1' position of a five-carbon sugar, a nucleoside is produced. The 5' carbon of the sugar in a nucleoside molecule is bonded to the 5' carbon of the sugar...

### Name the linkage connecting monosaccharide units in polysaccharides.

Glycosidic linkages connect the monosaccharide units of polysaccharides. When an oxide bond is created between two monosaccharide units with the loss of a water molecule, it is called a glycosidic...

### Under what conditions glucose is converted to gluconic and saccharic acid?

When glucose is treated with a mild oxidising agent like Br2 water, it is transformed to gluconic acid, a six-carbon carboxylic acid. When glucose is treated with nitric acid, it is transformed to...

### Monosaccharides contain carbonyl group hence are classified, as aldose or ketose. The number of carbon atoms present in the monosaccharide molecule is also considered for classification. In which class of monosaccharide will you place fructose?

Carbonyl groups can be found in monosaccharides. As a result, they're categorised as either aldose or ketose. Aldose refers to monosaccharides that contain an aldehyde group. Ketose refers to...

### The letters ‘D’ or ‘L’ before the name of a stereoisomer of a compound indicates the correlation of configuration of that particular stereoisomer. This refers to their relationship with one of the isomers of glyceraldehyde. Predict whether the following compound has ‘D’ or ‘L’ configuration.

On the left side of the C5 carbon atom, the –OH group is connected. As a result, the provided compound is in the 'L' configuration.

### Aldopentoses named as ribose and 2-deoxyribose are found in nucleic acids. What is their relative configuration?

D-configuration is the configuration of both aldopentoses. -D-ribose is ribose, while -D-2-deoxyribose is 2-deoxyribose.

### Which sugar is called invert sugar? Why is it called so?

Invert sugar is another name for sucrose. It comes from sugarcane and sugarbeet and is a naturally occurring sugar. When sucrose is hydrolyzed, the sign of rotation changes from Dextro (+) to laevo...

### Amino acids can be classified as α-, β-, -, δ- and so on depending upon the relative position of the amino group concerning the carboxyl group. Which type of amino acids forms polypeptide chain in proteins?

The sort of amino acids that make up a polypeptide chain are -amino acids and alpha-amino acids, where the amino acid is linked to the -carbon in the molecule.

### α-Helix is a secondary structure of proteins formed by twisting of the polypeptide chain into right-handed screw-like structures. Which type of interactions is responsible for making the a-helix structure stable?

The –NH group of each amino acid residue hydrogen is bound to the –C=O of an adjacent turn of the helix, forming a right-handed screw helix shape.

### Some enzymes are named after the reaction, where they are used. What name is given to the class of enzymes which catalyse the oxidation of one substrate with simultaneous reduction of another substrate?

Enzyme oxidoreductases is the name given to a group of enzymes that catalyse redox processes. Alcohol Dehydrogenase, for example, aids in the reduction of alcohol levels in the human body when...