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

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

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

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

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

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

168.

Half-life period of a radioactive element is 100 yr. How long will it take for its 93. 75% decay?

• 400yr

• 300yr

• 200yr

• 193yr

The unit of rate constant of a second order reaction is

• mol/L-s

• L/mol-s

• L²/mol²-s

• per second

2N₂O₅ $\rightleftharpoons$ 4NO₂ + O₂

For the above reaction which of the following is not correct about rates of reaction?

• $\frac{-\mathrm{d}\left[{\mathrm{N}}_2{\mathrm{O}}_5\right]}{\mathrm{dt}}= 2\frac{\mathrm{d}\left[{\mathrm{O}}_2\right]}{\mathrm{dt}}$

• $\frac{-2\mathrm{d}\left[{\mathrm{N}}_2{\mathrm{O}}_5\right]}{\mathrm{dt}}= \frac{\mathrm{d}\left[{\mathrm{NO}}_2\right]}{\mathrm{dt}}$

• $\frac{-\mathrm{d}\left[{\mathrm{NO}}_2\right]}{\mathrm{dt}}= 4\frac{\mathrm{d}\left[{\mathrm{O}}_2\right]}{\mathrm{dt}}$

• $\frac{-2\mathrm{d}\left[{\mathrm{N}}_2{\mathrm{O}}_5\right]}{\mathrm{dt}}= 4\frac{\mathrm{d}\left[{\mathrm{NO}}_2\right]}{\mathrm{dt}}= \frac{\mathrm{d}\left[{\mathrm{O}}_2\right]}{\mathrm{dt}}$