Consider the complex ions,
trans-[Co(en)₂Cl₂]⁺ (A) and
cis-[Co(en)₂Cl₂]⁺ (B).
The correct statement regarding them is :

For a reaction X + Y ⇌ 2Z , 1.0 mol of X, 1.5 mol
of Y and 0.5 mol of Z were taken in a 1 L vessel and
allowed to react. At equilibrium, the concentration
of Z was 1.0 mol L^–1. The equilibrium constant of reaction
is $${x \over {15}}$$. The value of x is _________.

For a dimerization reaction,
2A(g) $$ \to $$ A₂(g)
at 298 K, $$\Delta $$U^o = –20 kJ mol^–1, $$\Delta $$S^o = –30 JK^–1 mol^–1,
then the $$\Delta $$G^o will be _____ J.

Among the following compounds, geometrical isomerism is exhibited by :