8.0 g of a radioactive substance remains 0.5 g in 1 h. What is its half-life period?

• 10min

• 15min

• 30min

• None of these

The reaction A → B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 h. What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B?

• 1 h

• 0.5 h

• 0.25 h

• 2 h

1.0 L of 2.0 M acetic acid is mixed with 1.0 L of 3.0 Methyl alcohol. The reaction is CH₃COOH + C₂H₅OH $\rightleftharpoons$ CH₂COOC₂H₅ + H₂O. 1.0 L of 2.0 M acetic acid is mixed with 1.0 L of 3.0 Methyl alcohol. The reaction is

• 0.5 times

• 2.0 times

• 4.0 times

• 0.25 times

The time of completion of 90% of a first order reaction is approximately

• 1.1 times that of half-life

• 2.2 times that of half-life

• 3.3 times that of half-life

• 4.4 times that of half-life

The rate of reaction between two reactants A and B decreases by a factor of 4, if the concentration of reactant B is doubled. The order of this reaction with respect to reactant B is

• 2

• -1

• 1

• -2

In a first-order reaction A → B, if k is rate constant and initial concentration of reactant A is 0.5 M then, the half-life is

• $\frac{\ln 2}{\mathrm{k}}$

• $\frac{0.693}{0.5}$

• $\frac{\log 2}{2\mathrm{k}}$

• $\frac{\log 2}{\mathrm{k} \sqrt{0.5}}$

The velocity constant for a reaction is 0.693 × 10^-1 min^-1 and intial concentration is 0.2 mol/L, the half-life periods is

• 400s

• 600s

• 800s

• 100s

468.

For the chemical reaction N₂ + 3H₂ → 2NH₃, if $\frac{\mathrm{d}\left[{\mathrm{NH}}_3\right]}{\mathrm{dt}} = 2\times {10}^{-4} \mathrm{mol} {\mathrm{L}}^{-1} {\mathrm{s}}^{-1}, \mathrm{the}\hspace{0.17em}\mathrm{value}\hspace{0.17em}\mathrm{of}\hspace{0.17em}\frac{-\mathrm{d}\left[{\mathrm{H}}_2\right]}{\mathrm{dt}} \mathrm{is}$

•  1 × 10^-4 mol L^-1 s^-1

• 3 × 10^-4 mol L^-1 s^-1

• 4 × 10^-4 mol L^-1 s^-1

• 6 × 10^-4 mol L^-1 s^-1

If 2.0 g of a radioactive substance has half-life of 7 days, the half-life of 1 g sample is

• 7 days

• 14 days

• 28 days

• 35 days

The decay constant of a radioactive sample is λ. The half-life and mean life of the sample are, respectively

• $\frac{1}{\mathrm{\lambda }}; \ln \frac{2}{\mathrm{\lambda }}$

• $\ln \frac{2}{\mathrm{\lambda }}; \frac{1}{\mathrm{\lambda }}$

• $\mathrm{\lambda } \ln 2; \frac{1}{\mathrm{\lambda }}$

• $\frac{\mathrm{\lambda }}{\ln 2}; \frac{1}{\mathrm{\lambda }}$