CBSE Class 12 Chemistry — Short Answer Questions

Give reasons for the following: (3 × 1) (a) Carboxylic acids have higher boiling point than alcohols of comparable molecular masses. (b) Alpha (α) hydrogens of aldehydes and ketones are acidic in nature. (c) Nucleophilic addition of ammonia and its derivatives does not occur with carbonyl group in strongly acidic medium.

Write the reaction involved in the following: (3 × 1) (a) Reimer-Tiemann reaction (b) Kolbe's reaction (c) Friedel-Crafts acylation of anisole

(a) Answer the following: (3 × 1) (i) Why is the Equilibrium Constant (Kc) related to E°cell and not to Ecell? (ii) Two metals 'A' and 'B' have standard electrode potential values of −0.24 V and +0.80 V respectively. Which of these will liberate hydrogen gas from dil. H₂SO₄? (iii) Write the cell reaction which occurs in lead storage battery when it is in charging. OR (b) What type of battery is Mercury cell? Why it is more advantageous than dry cell? Write overall reaction taking place in Mercury cell.

Write the reactions of D-Glucose with the following: (3 × 1) (a) HI (b) Br₂ water (c) Conc. HNO₃

Compound 'X' with molecular formula C₄H₉Br reacts with aqueous KOH to give an alcohol. The rate of this reaction depends only on the concentration of the compound 'X'. When an optically active isomer 'Y' of the compound 'X' was treated with aqueous KOH solution, the rate of reaction was found to be dependent on concentration of compound 'Y' and aqueous KOH both. (3 × 1) (a) Write down the structural formula of both 'X' and 'Y'. (b) Out of 'X' and 'Y', which one will undergo racemisation and why? (c) Out of 'X' and 'Y', which one will form product with inversion of configuration and why?

For the first order thermal decomposition reaction, following data was obtained: C₂H₅Cl(g) → C₂H₄(g) + HCl(g) | S. No. | Time(s) | Total Pressure (atm) | | 1 | 0 | 0.30 | | 2 | 30 | 0.50 | Calculate rate constant. [Given: $\log 3 = 0.48$]

Calculate the boiling point of a solution containing 0.61 g of benzoic acid ($\text{Molar mass} = 122 \text{ g mol}^{-1}$) in 5 g of CS₂ in which it dimerises to the extent of 88%. The boiling point and Kb of CS₂ are 46.2 °C and $2.3 \text{ K kg mol}^{-1}$ respectively.