Which of the following statement is correct about the half-life period?

1. It is proportional to initial concentration of zero order reaction
2. Half-life period can be used to determine the order of the reaction
3. Half-life period for 1^st order reaction is independent of concentration
4. Catalyst does not affect half-life time period

Choose the correct answer from the options given below:

A, B and C only

The correct answer is 3. A, B and C only.

Half-life period is the time required for the concentration of a reactant to decrease to half of its initial value. It is a characteristic property of a reaction and does not depend on the initial concentration of the reactants (for first order reactions).

A. Half-life period is proportional to initial concentration of zero order reaction.

This is correct. For a zero order reaction, the half-life period is given by the following equation:

\(t_{1/2} = \frac{[R]_0}{2k}\)

where \([R]_0\) is the initial concentration of the reactant and k is the rate constant.

B. Half-life period can be used to determine the order of the reaction.

This is also correct. The half-life period of a first order reaction is independent of the initial concentration of the reactants, while the half-life period of a zero order reaction is proportional to the initial concentration of the reactants. Therefore, the order of a reaction can be determined by measuring the half-life period at different initial concentrations of the reactants.

C. Half-life period for 1st order reaction is independent of concentration.

This is also correct. The half-life period of a first order reaction is given by the following equation:

\(t_{1/2} = \frac{0.693}{k}\)

where k is the rate constant. As you can see, the initial concentration of the reactants does not appear in this equation.

D. Catalyst does not affect half-life time period.

This is incorrect. A catalyst increases the rate of a reaction without being consumed itself. Therefore, a catalyst will decrease the half-life period of a reaction.