Take $R = 8.314 J mo l^{- 1} K^{- 1}$ . A gas-phase reaction has $K = 20$ at $500 K$ . Which statements are correct?

A $Δ G^{\circ} = - 12.45 kJ mo l^{- 1}$
BFor a mixture with $Q = 0.50$ , $Δ G = - 15.33 kJ mo l^{- 1}$ and the forward reaction is spontaneous
CFor a mixture with $Q = 100$ , $Δ G = 6.69 kJ mo l^{- 1}$ and the forward reaction is spontaneous
DFor a mixture with $Q = 20$ , $Δ G = Δ G^{\circ}$

Answer: A, B

Δ G^{\circ} = - RT ln 20 = - (4157) (2.9957) /1000 = - 12.45 kJ mo l^{- 1}

Δ G = RT ln (Q / K)

: for

Q = 0.50

it is -15.33 kJ/mol (negative, forward spontaneous). For

Q = 100

it is 6.69 kJ/mol, positive, so the backward reaction is spontaneous and C is false. At

Q = K = 20

Δ G = 0

, not

Δ G^{\circ}