PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions for Chemistry

Write the equation of the reaction of hydrogen iodide with benzyl ethyl ether.

Explain the fact that in aryl alkyl ethers 

1. the alkoxy group activates the benzene ring towards electrophilic substitution and
2. it directs the incoming substituents to ortho and para positions in the benzene ring.

Give the uses of freon 12.

How the following conversion can be carried out?

Isopropyl alcohol to iodoform

How the following conversion can be carried out?

Aniline to phenylisocyanide

Give one example each of lyophobic sol and lyophilic sol.

Aqueous copper sulphate solution (blue in colour) gives a bright green solution with aqueous potassium chloride. Explain this experimental result.

Give the uses of DDT.

Give the uses of carbon tetrachloride.

Give the uses of iodoform.

What are lyophilic and lyophobic colloids ? Which of these sols can be easily coagulated on the addition of small amounts of electrolytes?

Define the following terms: Lyophilic colloid

Write a method by which lyophobic colloids can be coagulated.

Calculate the amount of CaCl₂ (molar mass = 111 g mol⁻¹) which must be added to 500 g of water to lower its freezing point by 2 K, assuming CaCl₂ is completely dissociated. (K_f for water = 1.86 K kg mol⁻¹)

Complete the equation

PbS + O₃ ⟶

Out of sulphur sol and proteins, which one form multimolecular colloids?

Account for the following :

Ozone is thermodynamically unstable.

Calculate the freezing point of solution when 1.9 g of MgCl₂ (M = 95 g mol⁻¹) was dissolved in 50 g of water, assuming MgCl₂ undergoes complete ionization.

(K_f for water = 1.86 K kg mol⁻¹)

When 2.56 g of sulphur was dissolved in 100 g of CS₂, the freezing point lowered by 0.383 K. Calculate the formula of sulphur (S_x).

(K_f for CS₂ = 3.83 K kg mol⁻¹, Atomic mass of sulphur = 32 g mol⁻¹]

Give reasons for the following observations: Lyophilic sol is more stable than lyophobic sol.