Science (English Medium) Class 12 - CBSE Important Questions for Chemistry

Henry’s law constant for CO₂ in water is 1.67 × 10⁸ Pa at 298 K. Calculate the quantity of CO₂ in 500 mL of soda water when packed under 2.5 atm CO₂ pressure at 298 K.

Define the term abnormal molar mass.

Write one difference in Solution and Colloid

Define the following term: 

Colligative properties

The vapour pressure of pure liquid X and pure liquid Y at 25°C are 120 mm Hg and 160 mm Hg respectively. If equal moles of X and Y are mixed to form an ideal solution, calculate the vapour pressure of the solution.

What happens if external potential applied becomes greater than E°cell of electrochemical cell?

The conductivity of 0.20 mol L⁻¹ solution of KCl is 2.48 × 10⁻² S cm⁻¹. Calculate its molar conductivity and degree of dissociation (α). Given λ⁰ (K⁺) = 73.5 S cm² mol⁻¹ and λ⁰ (C1⁻) = 76.5 S cm² mol⁻¹.

What type of battery is mercury cell? Why is it more advantageous than dry cell?

Why does the conductivity of a solution decrease with dilution?

Name the type of cell which was used in Apollo space programme for providing electrical power.

State second law of electrolysis

What advantage do the fuel cells have over primary and secondary batteries?

Which of the following solutions of KCl will have the highest value of molar conductivity?

Give reasons:

Mercury cell delivers a constant potential during its life time.

The rate constant of a first order reaction increases from 2 × 10⁻² to 4 × 10⁻² when the temperature changes from 300 K to 310 K. Calculate the energy of activation (E_a).

(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)

The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate the energy of activation of the reaction assuming that it does not change with temperature.

For a reaction R ---> P, half-life (t_1/2) is observed to be independent of the initial concentration of reactants. What is the order of reaction?

Define the following term:

Pseudo first-order reaction

For a reaction
\[\ce{2H2O2->[I^-][Alkaline medium]2H2O + O2}\]

The Proposed mechanism is given below: 
(1) H₂O₂+I^- → H₂O+IO^-(slow)
(2) H₂O₂+IO^-→H₂O+I^-+O₂(fast)

(i) Write the rate law for the reaction.
(ii) Write the overall order of a reaction.
(iii) Out of steps(1) and (2), which one is the rate-determining step? 

The decomposition of NH₃ on a platinum surface is a zero-order reaction. If the rate constant (k)  is 4 x 10^-3 ms^-1, how long will it take to reduce the initial concentration of NH₃ from 0.1 M to 0.064 M?