CBSE Class 12 Chemistry Solved Question Paper 2012

Define ‘peptization’.

Express the relation among cell constant, the resistance of the solution in the cell and conductivity of the solution. How is molar conductivity of a solution related to its conductivity?

A reaction is of second order with respect to a reactant. How is its rate affected if the concentration of the reactant is (i) doubled (ii) reduced to half?

Explain the role of each of the following:

(i) NaCN in the extraction of silver

(ii) SiO₂ in the extraction of copper

How is copper extracted from a low-grade ore of it?

Explain the following facts giving appropriate reason in each case:

(i) NF₃ is an exothermic compound whereas NCl₃ is not.

(ii) All the bonds in SF₄ are not equivalent.

What is the basicity of H₃PO₂ acid and why?

The molar conductivity of a 1.5 M solution of an electrolyte is found to be 138.9S cm²mol^-1. Calculate the conductivity of the conductivity of this solution.

What are n-types semiconductors?