Question

The standard Gibbs energy change at $300 \,K$ for the reaction $2 A \to B+C$ is $2494.2]$. At a given time, the composition of the reaction mixture is $[ A ]=\frac{1}{2},[ B ]=2$ and $[ C ] =\frac{1}{2} .$ The reaction proceeds in the : $[ R =8.314\, J / \,K /\, mol , e =2.718]$

• A. forward direction because $Q > K_c$
• B. reverse direction because $Q> K_c$
• C. forward direction because $Q < K_c$
• D. reverse direction because $Q < K_c$

Answer 1

Answer: (B)

reverse direction because $Q> K_c$

Answer 2

$\Delta G^{\circ}$ at $300\, K =2494.2 \,J$
$\Delta G ^{0}=- RT \ell n K$
$-2494.2=-8.314 \times 300 \,\ell\, n\, K$
$K =10$
$Q =\frac{[ B ][ C ]}{[ A ]^{2}}=\frac{2 \times \frac{1}{2}}{\left(\frac{1}{2}\right)^{2}}=4$
$Q > K _{ c } \Rightarrow$ reverse direction.