Rate law, rate constant, order and molecularity — practice questions

Question 1 · difficulty L2 · understanding

Rate law for a reaction between $A$ and $B$ is given by $$\mathrm{r}=\mathrm{k}[\mathrm{~A}]^{\mathrm{n}}[\mathrm{~B}]^{\mathrm{m}}$$ If concentration of $A$ is doubled and concentration of $B$ is halved from their initial value, the ratio of new rate of reaction to the initial rate of reaction $\left(\frac{r_2}{r_1}\right)$ is

• A. $(\mathrm{n}-\mathrm{m})$
• B. $2^{(\mathrm{n}-m)}$
• C. $\frac{1}{2^{m+n}}$
• D. $(\mathrm{m}+\mathrm{n})$

Question 2 · difficulty L2 · understanding

For a reaction of order n, the unit of the rate constant is :

• A. mol 1$$-$$n L 1$$-$$n s
• B. mol 1$$-$$n L 2n s $$-$$1
• C. mol 1$$-$$n L n$$-$$1 s $$-$$1
• D. mol 1$$-$$n L 1$$-$$n s $$-$$1

Question 3 · difficulty L2 · understanding

Given above is the concentration vs time plot for a dissociation reaction : $\mathrm{A} \rightarrow \mathrm{nB}$. Based on the data of the initial phase of the reaction (initial 10 min ), the value of n is $\_\_\_\_$ .

• A. 2
• B. 5
• C. 4
• D. 3

Question 4 · difficulty L2 · understanding

For a chemical reaction $$\mathrm{A}+\mathrm{B} \rightarrow$$ Product, the order is 1 with respect to $$\mathrm{A}$$ and $$\mathrm{B}$$. $$\mathrm{Rate}$$ $$\mathrm{mol~L^{-1}~S^{-1}}$$ $$\mathrm{[A]}$$ $$\mathrm{mol~L^{-1}}$$ $$\mathrm{[B]}$$ $$\mathrm{mol~L^{-1}}$$ 0.10 20 0.5 0.40 $$x$$ 0.5 0.80 40 $$y$$ What is the value of $$x$$ and $$y$$ ?

• A. 80 and 4
• B. 160 and 4
• C. 80 and 2
• D. 40 and 4

Question 5 · difficulty L2 · understanding

For kinetic study of the reaction of iodide ion with $$\mathrm{H}_{2} \mathrm{O}_{2}$$ at room temperature : (A) Always use freshly prepared starch solution. (B) Always keep the concentration of sodium thiosulphate solution less than that of KI solution. (C) Record the time immediately after the appearance of blue colour. (D) Record the time immediately before the appearance of blue colour. (E) Always keep the concentration of sodium thiosulphate solution more than that of KI solution. Choose the correct answer from the options given below :

• A. $$(\mathrm{A}),(\mathrm{B}),(\mathrm{C})$$ only
• B. $$(\mathrm{A}),(\mathrm{D}),(\mathrm{E})$$ only
• C. $$(\mathrm{D}),(\mathrm{E})$$ only
• D. $$(\mathrm{A}),(\mathrm{B}),(\mathrm{E})$$ only

Question 6 · difficulty L2 · understanding

For a reaction $\mathrm{A} \rightarrow \mathrm{P}$ at T K , the half life $\left(\mathrm{t}_{1 / 2}\right)$ is plotted as a function of initial concentration $[\mathrm{A}]_0$ of A as given below. The value of $x$ in the given figure is $\_\_\_\_$ s (Nearest integer)

Question 7 · difficulty L2 · understanding

Given below are two statements : Statement I : The rate law for the reaction $$A+B \rightarrow C$$ is rate $$(r)=k[A]^2[B]$$. When the concentration of both $$\mathrm{A}$$ and $$\mathrm{B}$$ is doubled, the reaction rate is increased "$$x$$" times. Statement II : The figure is showing "the variation in concentration against time plot" for a "$$y$$" order reaction. The Value of $$x+y$$ is __________.

Question 8 · difficulty L2 · understanding

Consider the following data for the given reaction $$2 \mathrm{HI}_{(\mathrm{g})} \rightarrow \mathrm{H}_{2(\mathrm{~g})}+\mathrm{I}_{2(\mathrm{~g})}$$ The order of the reaction is _________.

Question 9 · difficulty L2 · understanding

For conversion of compound A $$\to$$ B, the rate constant of the reaction was found to be $$\mathrm{4.6\times10^{-5}~L~mol^{-1}~s^{-1}}$$. The order of the reaction is ____________.

Question 10 · difficulty L2 · understanding

The reaction between X and Y is first order with respect to X and zero order with respect to Y. Experiment $${{[X]} \over {mol\,{L^{ - 1}}}}$$ $${{[Y]} \over {mol\,{L^{ - 1}}}}$$ $${{Initial\,rate} \over {mol\,{L^{ - 1}}\,{{\min }^{ - 1}}}}$$ I 0.1 0.1 $$2 \times {10^{ - 3}}$$ I L 0.2 $$4 \times {10^{ - 3}}$$ III 0.4 0.4 $$M \times {10^{ - 3}}$$ IV 0.1 0.2 $$2 \times {10^{ - 3}}$$ Examine the data of table and calculate ratio of numerical values of M and L. (Nearest Integer)