Board Paper of Class 12-Science 2011 Chemistry (SET 3) - Solutions

What type of a battery is lead storage battery? Write the anode and the cathode reactions and the overall reactions occurring in a lead storage battery.

Two half-reactions of an electrochemical cell are given below:

Construct the redox equation from the standard potential of the cell and predict it the reaction is reactant favoured or product favoured.

State reasons for each of the following: 

(i) The N − O bond in is shorter than the N − O bond in

(ii) SF₆ is kinetically an inert substance. 

OR

State reasons for each of the following: 

(i) All the P-Cl bonds in PCl₅ molecule are not equivalent. 

(ii) Sulphur has greater tendency for catenation than oxygen.

Distinguish between ‘rate expression’ and ‘rate constant’ of a reaction.

Assign reasons for each of the following: 

(i) Transition metals generally form coloured compounds. 

(ii) Manganese exhibits the highest oxidation state of +7 among the 3d series of transition elements. 

How would you obtain 

(i) Picric acid (2, 4, 6-trinitrophenol) from phenol, 

(ii) 2-Methylpropene from 2-methylpropanol? 

Explain the following giving one example for each: 

(i) Reimer-Tiemann reaction. 

(ii) Friedel Craft’s acetylation of anisole.

Describe what you understand by primary structure and secondary structure of proteins.

What is essentially the difference between α-form of glucose and β-form of glucose? Explain.

Name the sub-groups into which polymers are classified on the basis of magnitude of intermolecular forces.

The density of lead is 11.35 g cm⁻³ and the metal crystallizes with fcc unit cell. Estimate the radius of lead atom (At. Mass of lead = 207 g mol⁻¹ and N_A = 6.02 × 10²³ mol⁻¹) 

Explain how the phenomenon of adsorption finds application in each of the following processes:

(i) Production of vacuum

(ii) Heterogeneous catalysis

(iii) Froth Floatation process

OR

Define each of the following terms:

(i) Micelles

(ii) Peptization

(iii) Desorption

Nitrogen pentoxide decomposes according to equation: 2N₂O₅(g) → 4NO₂(g) + O₂(g) 

This first order reaction was allowed to proceed at 40° C and the data below were collected:

(a) Calculate the rate constant. Include units with your answer. 

(b) What will be the concentration of N₂O₅ after 100 minutes? 

(c) Calculate the initial rate of reaction.

Complete the following chemical equations:

(i)

(ii)

(iii)

Write the name, stereochemistry and magnetic behaviour of the following: 

(At. nos. Mn = 25, Co = 27, Ni = 28) 

(i) K₄[Mn(CN)₆] 

(ii) [Co(NH₃)₅Cl]Cl₂

(iii) K₂[Ni(CN)₄]

Describe the principle behind each of the following processes:

(i) Vapour phase refining of a metal.

(ii) Electrolytic refining of a metal.

(iii) Recovery of silver after silver ore was leached with NaCN.

Answer the following: 

(i) Haloalkanes easily dissolve in organic solvents, why? 

(ii) What is known as a racemic mixture? Give an example. 

(iii) Of the two bromoderivatives, C₆H₅CH(CH₃)Br and C₆H₅CH(C₆H₅)Br, which one is more reactive in substitution reaction and why? 

Complete the following chemical equations: 

(i)

(ii) C₆H₅N₂Cl + H₃PO₂ + H₂O →

(iii) 

Answer the following questions: 

(i) Why do soaps not work in hard water? 

(ii) What are the main constituents of dettol? 

(iii) How do antiseptics differ from disinfectants?

(a) Give chemical tests to distinguish between 

(i) Propanal and propanone, 

(ii) Benzaldehyde and acetophenone. 

(b) How would you obtain 

(i) But-2-enal from ethanal, 

(ii) Butanoic acid from butanol, 

(iii) Benzoic acid from ethylbenzene? 

OR

(a) Describe the following giving linked chemical equations: 

(i) Cannizzaro reaction 

(ii) Decarboxylation 

(b) Complete the following chemical equations: 

(i) 

(ii) 

(iii)

(a) Explain the following: 

(i) NF₃ is an exothermic compound whereas NCl₃ is not. 

(ii) F₂ is most reactive of all the four common halogens. 

(b) Complete the following chemical equations: 

(i) C + H₂SO₄ (conc) →

(ii) P₄ + NaOH + H₂O →

(iii)

OR

(a) Account for the following: 

(i) The acidic strength decreases in the order HCl > H₂S > PH₃

(ii) Tendency to form pentahalides decreases down the group in group 15 of the periodic table. 

(b) Complete the following chemical equations: 

(i) P₄ + SO₂Cl₂ →

(ii) XeF₂ + H₂O →

(iii)

(a) Differentiate between molarity and molality for a solution. How does a change in temperature influence their values? 

(b) Calculate the freezing point of an aqueous solution containing 10.50 g of MgBr₂ in 200 g of water. (Molar mass of MgBr₂ = 184 g) (K_f for water = 1.86 K kg mol⁻¹) 

OR

(a) Define the terms osmosis and osmotic pressure. Is the osmotic pressure of a solution a colligative property? Explain. 

(b) Calculate the boiling point of a solution prepared by adding 15.00 g of NaCl to 250.0 g of water. (K_b for water = 0.512 K kg mol⁻¹), (Molar mass of NaCl = 58.44 g)