For a general reaction $A \to B$,a plot of the concentration of $A$ versus time is given in the figure. Answer the following questions based on this graph:
$(i)$ What is the order of the reaction?
$(ii)$ What is the slope of the curve?
$(iii)$ What are the units of the rate constant?

(N/A) $(i)$ The reaction is a zero-order reaction because the plot of concentration versus time is a straight line with a negative slope.
$(ii)$ For a zero-order reaction,the integrated rate equation is $[A] = -kt + [A]_0$. Comparing this to the equation of a straight line $y = mx + c$,the slope is $-k$.
$(iii)$ The units of the rate constant for a zero-order reaction are $mol \ L^{-1} \ s^{-1}$.