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

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?

Write the main product(s) in each of the following reactions:

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. 

How the supersonic jet aeroplanes are responsible for the depletion of ozone layers?

Calculate the freezing point of the solution when 31 g of ethylene glycol (C₂H₆O₂) is dissolved in 500 g of water.

(K_f for water = 1.86 K kg mol^–1)

Define the following term:

Multimolecular colloids

Define the following term as related to proteins:

Denaturation

Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.

Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.

Calculate the mass of ascorbic acid (Vitamin C, C₆H₈O₆) to be dissolved in 75 g of acetic acid to lower its melting point by 1.5°C. K_f = 3.9 K kg mol⁻¹.

A 5% solution (by mass) of cane sugar in water has freezing point of 271 K. Calculate the freezing point of 5% glucose in water if freezing point of pure water is 273.15 K.