Question

Which of the following graphs is true for zero order reaction?

• A.
• B.
• C. Both (a) and (b)
• D.

Answer 1

The correct option is C Both (a) and (b)

Consider a zero order reaction,
$A\to Product$
$\text{Rate,}R=K[A{]}^0$
$-\frac{d\left[A\right]}{dt}=K[A{]}^0$
$-\frac{d\left[A\right]}{dt}=K\times 1$
$-d\left[A\right]=Kdt$
Taking limit on both side
$-\underset{[a{]}_0}{\overset{[A{]}_t}{\int }}d\left[A\right]=K\underset{0}{\overset{t}{\int }}dt$

when,
$time=0,A=[A{]}_o$
$time=t,A=[A{]}_t$

$-[A{]}_{[A{]}_o}^{[A{]}_t}=K[t{]}_0^t$

$[A{]}_0-[A{]}_t=Kt$

$[A{]}_t=[A{]}_0-Kt$

Its in $y=mx$ form.

Hence,
Plot between $[A{]}_t$ vs time :

For zero order reaction,
$\text{Rate,}R=K\left(\text{Rate constant}\right)$
$\therefore$
Rate of Zero order reaction is equal to Rate constant of that reaction, which is independent of concentration. Hence, on increasing concentration of reactants, rate of reaction does not increase.
Plot of Rate Vs Concentration: