The Arrhenius equation is given by: k = A e$^{-E_a/RT}$ Taking natural log on both sides: ln $k$ = ln $A$ − $\dfrac{E_a}{R} \cdot \dfrac{1}{T}$ This is in the form of a straight line $y = mx + c$, where the slope is $-E_a/R$. Hence, a plot of ln $k$ vs. $\dfrac{1}{T}$ gives a straight line with slope equal to $-E_a/R$.