Question

Predict whether the reaction
$CO\left(g\right)+\left(\frac{1}{2}\right)O_2\left(g\right)\to C{O}_2\left(g\right)$ at 300 K is spontaneous & exothermic or non-spontaneous & endothermic, when the standard entropy change is $-0.094kJmo{l}^{-1}{K}^{-1}.$ The standard Gibb's free energies of formation for $C{O}_2$ and $CO$ are $-394.4and-137.2kJmo{l}^{-1}$ respectively.

• A. value of $△H^o$ is negative so the given reaction is non-spontaneous and endothermic.
• B. value of $△H^o$ is positive so the given reaction is non-spontaneous and endothermic.
• C. value of $△H^o$ is negative so the given reaction is spontaneous and exothermic.
• D. value of $△H^o$ is positive so the given reaction is spontaneous and exothermic.

Answer 1

The correct option is C value of $△H^o$ is negative so the given reaction is spontaneous and exothermic.

The given reaction is,
$CO\left(g\right)+\left(\frac{1}{2}\right)O_2\left(g\right)\to C{O}_2\left(g\right)$
for the reaction the Gibb's free energy is given by $△G^o=G_{C{O}_2}^o-G_{CO}^o-\left(\frac{1}{2}\right)G_{O_2}^o$
$=-394.4-(-137.2)-0$
$=-257.2kJmo{l}^{-1}$
from Helmholtz- Gibb's free energy equation
$△G^o=△H^o-T△S^o$
$-257.2=△H^o-300\times -\left(0.094\right)$
$△H^o=-229kJ$ is negative, hence the
since, value of $△H^o$ is negative (heat is releasing) so the given reaction is spontaneous and exothermic.