Chemical Kinetics - Result Question 2
####2. In the following reaction; $x A \rightarrow y B$
$\log _{10}\left[-\frac{d[A]}{dt}\right]=\log _{10}\left[\frac{d[B]}{dt}\right]+0.3010$
$A$ and $B$ respectively can be
(2019 Main, 12 April I)
(a) n-butane and iso-butane
(b) $C _2 H _2$ and $C _6 H _6$
(c) $C _2 H _4$ and $C _4 H _8$
(d) $N _2 O _4$ and $NO _2$
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Answer:
Correct Answer: 2. (c)
Solution:
- In the given reaction; $x A \longrightarrow y B$
$$ \log _{10}\left[\frac{-d[A]}{d t}\right]=\log _{10}\left[\frac{d[B]}{d t}\right]+0.3010 $$
Value of $\log 2=0.3010$
Substituting 0.3010 by $\log 2$
$$ \log _{10}\left[-\frac{d[A]}{d t}\right]=\log _{10}\left[\frac{d[B]}{d t}\right]+\log 2 $$
Using logarithm rules,
$$ \left[\frac{-d[A]}{d t}\right]=2 \times\left[\frac{d[B]}{d t}\right] \Rightarrow-\frac{1}{2}\left[\frac{d[A]}{d t}\right]=\left[\frac{d[B]}{d t}\right] $$
Using the rate equation (i) to determine the reaction involved is
$$ 2 A \longrightarrow B $$
Option that fits correct in the above reaction is (c).
$$ 2 C _2 H _4 \longrightarrow C _4 H _8 $$
