Question

Consider the following hypothetical reaction (at 375 K). The standard free energies in kJ/mol are given below each substance in parentheses.What is the value of the Gibbs free energy for the reaction at this temperature? Is the reaction spontaneous?

$\underset{(-20.0)}{2A}\to \underset{\left(150.0\right)}{B}+\underset{(-350.0)}{C}△G^{\circ }=?$

• A. $-$ 220; yes
• B. $-$ 180; no
• C. $-$ 160; yes
• D. $+$ 180; no
• E. $-$ 160; no

Answer 1

The correct option is C $-$ 160; yes

$\Delta G_{rxn}^o=\Delta G_B^o+\Delta G_C^o-2\Delta G_A^o$
$\Delta G_{rxn}^o=150.0-350.0-2(-20.0)$
$\Delta G_{rxn}^o=-160.0$ kJ/mol
Since the value of $\Delta G_{rxn}^o$ is negative, the reaction is spontaneous.