Question

The reaction; $2A+B+C\to D+2E$; is found to be I order in $A$, II order in $B$ and zero order in $C$.
(a) Write the rate expression.
(b) What is the effect on rate on increasing the conc. of $A,B$ and $C$ two times?

Answer 1

(a) $Rate=K\left[A{]}^1\right[B{]}^2[C{]}^0$

(b) Let initial conc. of $A,B$ and $C$ be $a,b$, and $c$ mol $litr{e}^{-1}$ respectively

Then, Rate $r_1=K{a}^1{b}^2{c}^0$

Now if conc. of $A,B$ and $C$ are doubled, i.e. $2a,2b$ and $2c$ respectively, then,

$r_2=K\left(2a{)}^1\right(2b{)}^2(2c{)}^0....(2)$

By eqs. (1) and (2), $\frac{r_1}{r_2}=\frac{1}{8}\therefore r_2=8r_1$.