31.

Blue colour of water in sea is due to :

• refraction of blue light by impurities in sea water

• refraction of blue sky by water

• scattering of light by impurities

• All of the above

In aerosol, the dispersion medium is :

• solid

• liquid

• gas

• all of the above

A reaction , 2A $\to$ products (x) is found to follow zero order kinetics .Then :

• $\frac{\mathrm{dx}}{\mathrm{dt}}= \mathrm{k} \left[\mathrm{A}\right]$

• $\frac{\mathrm{dx}}{\mathrm{dt}}=\mathrm{k} [\mathrm{A}{]}^0$

• $\frac{\mathrm{dx}}{\mathrm{dt}} = \mathrm{k} [\mathrm{A}{]}^2$

• $\frac{\mathrm{dx}}{\mathrm{dt}} = \mathrm{k} \left[2\mathrm{A}\right]$

The rate of a reaction is primarily determined by the slowest step .This step is called :

• rate determining step

• reaction rate

• activation step

• None of the above

HCl is a gas but HF is a low boiling liquid .This is because :

• H-F bond is strong

• H-F bond is weak

• molecules aggregate because of hydrogen bonding

• HF is a weak acid

Ostwald process is used for the manufacture of :

• nitric acid

• sulphuric acid

• ammonia

• bleaching powder

Which defect causes decrease in the density of crystal ?

• Frenkel

• Schottky

• Interstitial

• F-centre

For a dilute solution , Raoult's law states that :

• the lowering of vapour pressure is equal to mole fraction of solute

• the relative lowering of vapour pressure is equal to mole fraction of solute

• the relative lowering of vapour pressure is proportional to the amount of solute in solution

• the vapour pressure of the solution is equal to the mole fraction of solvent

A gaseous mixture contains 56 g N₂ , 44 g CO₂ and 16 g CH₄ .The total pressure of the mixture is 720 mm Hg .What is the partial pressure of CH₄ ?

• 142 mm

• 156 mm

• 182 mm

• 180 mm

The chemical used for cooling in refrigerators is :

• CO₂

• NH₄OH

• NH₄Cl

• liquid NH₃