81.

Which of the following is not a characteristic of chemisorption?

• $∆$H is of the order of 400 kJ

• Adsorption is irreversible

• Adsorption may be multimolecular layer

• Adsorption is specific

The concentration of electrolyte required to coagulate a given amount of As₂S₃ solution is minimum in the case of

• magnesium nitrate

• potassium nitrate

• potassium sulphate

• aluminium nitrate

In the manufacture of sulphuric acid by contact process, Tyndall box is used to

• filter dust particles

• remove impurities

• convert SO₂ to SO₃

• test the presence of dust particles

Pick out the statement which is not relevant in the discussion of colloids

• sodium aluminium silicate is used in the softening of hard water

• potash alum is used m shavmg rounds and as a styptic in medicine

• artificial rain is caused by throwing electrified sand on the clouds from an aeroplane

• deltas are formed at a place where the river pours its water into the sea

The diameter of colloidal particles range from

• 10^-6m to 10^-9m

• 10^-9m to 10^-12m

• 10³m to 10^-3m

• 10^-3m to 10^-6 m

Identify the gas which is readily adsorbed by activated charcoal

• N₂

• SO₂

• H₂

• O₂

A emulsifier is a substance which

• stabilises the emulsion

• homogenises the emulsion

• coagulates the emulsion

• accelerates the dispersion of liquid in liquid

The temperature of the system decreases in an

• adiabatic compression

• isothermal compression

• isothermal expansion

• adiabatic expansion

An example for autocatalysis is :

• oxidation of NO to NO₂

• oxidation of SO₂ to SO₃

• decomposition of KClO₃ to KCl and O₂

• oxidation of oxalic acid by acidified KMnO₄

2SO₂ (g) + O₂ (g) $\stackrel{{\mathrm{V}}_2{\mathrm{O}}_5}{\rightleftharpoons }$ is an example for 

• neutralisation reaction

• homogeneous catalysis

• heterogeneous catalysis

• irreversible reaction