CBSE Class 12 Chemistry 2019 — Set 56/2/1

Write balanced chemical equations for the following processes: (a) Cl₂ is passed through slaked lime. (b) SO₂ gas is passed through an aqueous solution of Fe(III) salt. OR (a) Write two poisonous gases prepared from chlorine gas. (b) Why does Cu²⁺ solution give blue colour on reaction with ammonia?

Give reasons: (a) Cooking is faster in pressure cooker than in cooking pan. (b) Red Blood Cells (RBC) shrink when placed in saline water but swell in distilled water.

Define order of reaction. Predict the order of reaction in the given graphs, where [R]₀ is the initial concentration of reactant and t1/2 is half-life: (a) A plot of t1/2 (y-axis) vs [R]₀ (x-axis) that is a horizontal straight line — t1/2 is independent of [R]₀. (b) A plot of t1/2 (y-axis) vs [R]₀ (x-axis) that is a straight line passing through the origin with a positive slope — t1/2 is directly proportional to [R]₀.

When FeCr₂O₄ is fused with Na₂CO₃ in the presence of air it gives a yellow solution of compound (A). Compound (A) on acidification gives compound (B). Compound (B) on reaction with KCl forms an orange coloured compound (C). An acidified solution of compound (C) oxidises Na₂SO₃ to (D). Identify (A), (B), (C) and (D).

Write IUPAC name of the complex [Co(en)₂(NO₂)Cl]^+. What type of structural isomerism is shown by this complex? OR Using IUPAC norms, write the formulae for the following complexes: (a) Hexaaquachromium(III) chloride (b) Sodium trioxalatoferrate(III)

(a) Although both [NiCl₄]²⁻ and [Ni(CO)₄] have sp³ hybridisation yet [NiCl₄]²⁻ is paramagnetic and [Ni(CO)₄] is diamagnetic. Give reason. (Atomic no. of Ni = 28) (b) Write the electronic configuration of d⁵ on the basis of crystal field theory when (i) Δo < P and (ii) Δo > P

Write structures of main compounds A and B in each of the following reactions: (a) C₆H₅COOH xrightarrowPCl₅ A xrightarrowH₂/Pd-BaSO₄ B (b) CH₃CN xrightarrow[(ii)H₃O^+](i)CH₃MgBr A xrightarrowZn(Hg)/conc. HCl B

The following data were obtained for the reaction A + 2B arrow C: Experiment 1: [A]=0.2 M, [B]=0.3 M, initial rate of formation of C =4.2 × 10⁻² M min⁻¹; Experiment 2: [A]=0.1 M, [B]=0.1 M, rate =6.0 × 10⁻³ M min⁻¹; Experiment 3: [A]=0.4 M, [B]=0.3 M, rate =1.68 × 10⁻¹ M min⁻¹; Experiment 4: [A]=0.1 M, [B]=0.4 M, rate =2.40 × 10⁻² M min⁻¹. (a) Find the order of reaction with respect to A and B. (b) Write the rate law and overall order of reaction. (c) Calculate the rate constant (k).

A solution containing 1.9 g per 100 mL of KCl (M = 74.5 g mol⁻¹) is isotonic with a solution containing 3 g per 100 mL of urea (M = 60 g mol⁻¹). Calculate the degree of dissociation of KCl solution. Assume that both the solutions have same temperature.

Give reasons for the following: (a) Transition metals form complex compounds. (b) E^° values for (Zn²⁺/Zn) and (Mn²⁺/Mn) are more negative than expected. (c) Actinoids show wide range of oxidation states.

Among all the isomers of molecular formula C₄H₉Br, identify (a) the one isomer which is optically active. (b) the one isomer which is highly reactive towards SN2. (c) the two isomers which give same product on dehydrohalogenation with alcoholic KOH.

Complete the following reactions: (a) Cyclobutanecarbonitrile (a cyclobutane ring bearing a -CN group) xrightarrowH₂/Ni (b) A benzene ring bearing a -CH₃ group, a -Br group ortho to it, and a -N₂^+Cl^- (diazonium) group para to the -CH₃ xrightarrowH₃PO₂ + H₂O (c) Benzylamine, C₆H₅CH₂NH₂ + CHCl₃ xrightarrowEthanolicKOH OR How do you convert the following: (a) N-phenylethanamide to p-bromoaniline (b) Benzene diazonium chloride to nitrobenzene (c) Benzoic acid to aniline

(a) Give reasons: (i) Benzoic acid is a stronger acid than acetic acid. (ii) Methanal is more reactive towards nucleophilic addition reaction than ethanal. (b) Give a simple chemical test to distinguish between propanal and propanone.

(a) What are the products of hydrolysis of maltose? (b) What type of bonding provides stability to α-helix structure of protein? (c) Name the vitamin whose deficiency causes pernicious anaemia. OR Define the following terms: (a) Invert sugar (b) Native protein (c) Nucleotide

(a) The conductivity of 0.001 mol L⁻¹ acetic acid is 4.95 × 10⁻⁵ S cm⁻¹. Calculate the dissociation constant if Lambdamo for acetic acid is 390.5 S cm² mol⁻¹. (b) Write Nernst equation for the reaction at 25^° C: 2Al(s) + 3Cu²⁺(aq) arrow 2Al³⁺(aq) + 3Cu(s) (c) What are secondary batteries? Give an example. OR (a) Represent the cell in which the following reaction takes place: 2Al(s) + 3Ni²⁺(0.1M) arrow 2Al³⁺(0.01M) + 3Ni(s). Calculate its emf if Eocell = 1.41 V. (b) How does molar conductivity vary with increase in concentration for strong electrolyte and weak electrolyte? How can you obtain limiting molar conductivity (Lambdamo) for weak electrolyte?

(a) Give equations of the following reactions: (i) Phenol is treated with conc. HNO₃. (ii) Propene is treated with B₂H₆ followed by H₂O₂/OH^-. (iii) Sodium t-butoxide is treated with CH₃Cl. (b) How will you distinguish between butan-1-ol and butan-2-ol? (c) Arrange the following in increasing order of acidity: Phenol, ethanol, water OR (a) How can you obtain Phenol from (i) Cumene, (ii) Benzene sulphonic acid, (iii) Benzene diazonium chloride? (b) Write the structure of the major product obtained from dinitration of 3-methylphenol. (c) Write the reaction involved in Kolbe's reaction.