Question

Which of the following graph is correct for a zero order reaction?

• A.
• B.
• C.
• D.

Answer 1

Answer: (B), (D)

Plot of rate of reaction vs time

Let’s consider the following zero-order reaction.

$A\to$ Products

Rate of reaction $=k[A{]}^0=k$

As rate constant is fixed for a given reaction at specific temperature and it doesn’t depend upon time.

Hence, the rate of reaction will be constant in a graph of reaction rate vs time. So, it will be a straight horizontal line.

After some time, when the concentration of reactant vanishes, then rate of reaction suddenly falls with time.


So, option $\left(A\right)$ is the correct plot while option $\left(C\right)$ is the incorrect plot for reaction rate vs time graph.

Plot of reactant concentration vs time

For a zero-order reaction,

$\left[A\right]=\left[A_0\right]-kt\dots \dots ..\left(1\right)$

Where,

$\left[A_0\right]=$ Initial concentration of reactant

$\left[A\right]=$ Remaining concentration of reactant at time $t$

$k=$ Rate constant

$t=$ time

On comparing equation $\left(1\right)$ with the equation of a straight line,

$y=c+mx$

It shows that, for the concentration of reactant vs time plot, the curve will be a straight line with negative slope $(-k).$



So, option $\left(D\right)$ will be the correct plot, while option $\left(B\right)$ will be the incorrect plot for the concentration of the reactant vs time graph.

Hence, options $\left(A\right)$ and $\left(D\right)$ are the correct answers.