$X(g) +Y(g) \rightleftharpoons Z(g)$
At equilibrium, it was observed that :
$[X]=\large\frac{1}{2} $$[Y]=\large\frac{1}{2}$$ [Z].$
What is the value of $[Z]$ (in mol $L^{-1}$) at equilibrium ?
\[\begin {array} {1 1} (a)\;2 \times 10^{-4} & \quad (b)\;10^{-4} \\ (c)\;2 \times 10^{4} & \quad (d)\;10^{4} \end {array}\]
