Chemical Kinetics MCQ Questions & Answers in Physical Chemistry | Chemistry
Learn Chemical Kinetics MCQ questions & answers in Physical Chemistry are available for students perparing for IIT-JEE, NEET, Engineering and Medical Enternace exam.
191.
The half-life of a reaction is inversely proportional to the square of the initial concentration of the reactant. Then the order of the reaction is
A
the order and molecularity of the slowest step are equal to one
B
molecularity of the reaction can be zero, one or two
C
more than one reacting species are involved in one step
D
molecularity of the reaction can be determined only experimentally.
Answer :
the order and molecularity of the slowest step are equal to one
For a unimolecular reaction, both order and molecularity are one in rate determining step.
193.
The rate constants $${k_1}$$ and $${k_2}$$ for two different reactions are $${10^{16}} \cdot {e^{\frac{{ - 2000}}{T}}}$$ and $${10^{15}} \cdot {e^{\frac{{ - 1000}}{T}}},$$ respectively. The temperature at which $${k_1} = {k_2}$$ is
195.
The rate constant for the reaction, $$2{N_2}{O_5} \to 4N{O_2} + {O_2}$$ is $$2 \times {10^{ - 5}}\,{s^{ - 1}}.$$ If rate of reaction is $$1.4 \times {10^{ - 5}}\,mol\,{L^{ - 1}}\,{s^{ - 1}},$$ what will be the concentration of $${N_2}{O_5}$$ in $$mol\,{L^{ - 1}}?$$
A
0.8
B
0.7
C
1.2
D
1
Answer :
0.7
Rate $$ = k\left[ {{N_2}{O_5}} \right]$$ ( first order as unit of rate constant is $${s^{ - 1}}$$ )
$$\eqalign{
& \left[ {{N_2}{O_5}} \right] = \frac{{{\text{rate}}}}{k} \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{1.4 \times {{10}^{ - 5}}\,mol\,{L^{ - 1}}\,{s^{ - 1}}}}{{2 \times {{10}^{ - 5}}\,{s^{ - 1}}}} \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 0.7\,mol\,{L^{ - 1}} \cr} $$
196.
The specific rate constant of a first order reaction depends on the
A
concentration of the reactant
B
concentration of the product
C
time
D
temperature
Answer :
temperature
It is a characteristic constant of a particular reaction at a given temperature. It does not depend upon initial concentration of the reactants, time of reaction and extent of reaction.
197.
In the reaction of formation of sulphur trioxide by contact process $$2S{O_2} + {O_2} \rightleftharpoons 2S{O_3}$$ the rate of reaction was measured as $$\frac{{d\left[ {{O_2}} \right]}}{{dt}} = - 2.5 \times {10^{ - 4}}\,mol\,{L^{ - 1}}{s^{ - 1}}.$$ The rate of reaction is terms of $$\left[ {S{O_2}} \right]$$ in $$mol\,{L^{ - 1}}{s^{ - 1}}$$ will be :
198.
$$A + 2B \to C,$$ the rate equation for this reaction is given as Rate $$ = K\left[ A \right]\left[ B \right].$$ If the concentration of $$A$$ is kept the same but that of $$B$$ is doubled what will happen to the rate itself ?
A
halved
B
the same
C
doubled
D
quadrupled
Answer :
doubled
$$\eqalign{
& {\text{Rate}} = k\left[ A \right]\left[ B \right] = R \cr
& R' = k\left[ A \right]\left[ {2B} \right] \cr
& \frac{R}{{R'}} = \frac{{k\left[ A \right]\left[ B \right]}}{{k\left[ A \right]\left[ {2B} \right]}} \cr
& = \frac{{k\left[ A \right]\left[ B \right]}}{{2k\left[ A \right]\left[ B \right]}} \cr
& \Rightarrow 2R = R'\,\,i.e.,\,{\text{rate become doubles}}{\text{.}} \cr} $$
199.
The rate equation for the reaction $$2A + B → C$$ is found to be : rate $$= k[A][B].$$ The correct statement in relation to this reaction is that the
A
rate of formation of $$C$$ is twice the rate of disappearance of $$A$$
B
$${t_{\frac{1}{2}}}$$ is a constant
C
unit of $$k$$ must be$${s^{ - 1}}$$
D
value of $$k$$ is independent of the initial concentrations of $$A$$ and $$B$$
Answer :
value of $$k$$ is independent of the initial concentrations of $$A$$ and $$B$$
The velocity constant depends on temperature only. It is independent of concentration of reactants.
200.
The decomposition of dimethyl ether is a fractional order reaction. The rate of reaction is given by $${\text{rate}} = {\text{k}}{\left( {{p_{_{C{H_3}OC{H_3}}}}} \right)^{\frac{3}{2}}}.$$ If the pressure is measured in bar and time in minutes, then what are the units of rate and rate constant?
A
\[\text{bar}\,{{\min }^{-1}},\,\text{ba}{{\text{r}}^{2}}\,{{\min }^{-1}}\]
B
\[\text{bar}\,{{\min }^{-1}},\,\text{ba}{{\text{r}}^{-\frac{1}{2}}}\,{{\min }^{-1}}\]
C
\[\text{ba}{{\text{r}}^{-\frac{1}{2}}}\,{{\min }^{-1}},\,\text{ba}{{\text{r}}^{2}}\,{{\min }^{-1}}\]
D
\[\text{bar}\,{{\min }^{-1}},\,\text{ba}{{\text{r}}^{\frac{1}{2}}}\,{{\min }^{-1}}\]