Question

For the chemical equilibrium, $CaC{O}_3\left(s\right)\rightleftharpoons CaO\left(s\right)+C{O}_2\left(g\right),△H^o,$ can be determined from which one of the following plots

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

For the reaction,
$CaC{O}_{3\left(g\right)}\rightleftharpoons Ca{O}_i+C{O}_{2\left(g\right)}$

$K_p=P_{C{O}_2}and{K}_C=\left[C{O}_2\right]$
([$CaC{O}_3]$ = 1 and [CaO] = 1 for solids]
According to Arrhenius equation we have
$K=A{e}^{△H^o,/RT}$
Taking logarithm, we have
log $K_p=logA-\frac{△H^o,}{RT\left(2.303\right)}$

This is an equation of straight line. When log $K_p$ is plotted against 1/T. We get a straight line.



The intercept fo this line = log A, slope = $-△H^o,/2.303R$
Knowing the value of slope from the plot and universal gas constant R, $△H_r^o$ can be calculated.

Equation of straight line : Y = mx + C. Here, log $K_p=-\frac{△H_r^o}{2.303R}\left(\frac{1}{T}\right)+logA$