Unit 4 Chemical Kinetics (Intext Questions-2)
Intext Questions
4.3 For a reaction, $\mathrm{A}+\mathrm{B} \rightarrow$ Product; the rate law is given by, $r=k[\mathrm{~A}]^{1 / 2}[\mathrm{~B}]^{2}$. What is the order of the reaction?
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Answer
The order of the reaction $=\frac{1}{2}+2$
$=2 \frac{1}{2}$
$=2.5$
4.4 The conversion of molecules $X$ to $Y$ follows second order kinetics. If concentration of $\mathrm{X}$ is increased to three times how will it affect the rate of formation of $\mathrm{Y}$ ?
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Answer
The reaction $X \rightarrow Y$ follows second order kinetics.
Therefore, the rate equation for this reaction will be:
Rate $=k[\mathrm{X}]^{2}(1)$
Let $[X]=a$ mol $L^{-1}$, then equation (1) can be written as:
Rate $_{1}=k .(a)^{2}$
$=k a^{2}$
If the concentration of $X$ is increased to three times, then $[X]=3 a \mathrm{~mol} \mathrm{~L}^{-1}$
Now, the rate equation will be:
Rate $=k(3 a)^{2}$
$=9\left(k a^{2}\right)$
Hence, the rate of formation will increase by 9 times.
