Question

Which of the following graphs represents an exothermic reaction?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

Using van 't Hoff equation,
$\frac{dln{K}_p}{dT}=\frac{\Delta H^{\circ }}{R{T}^2}$ or, $ln{K}_p=\frac{-\Delta H^{\circ }}{R}\frac{1}{T}+C$
This is a linear equation of the form $y=mx+C$ where $y=ln{K}_p$, $x=\frac{1}{T}$ and the slope m would be $\frac{-\Delta H^{\circ }}{R}$. Since $\Delta H$ is -ve (exothermic), the slope of the graph is positive.