A reversible chemical reaction at equilibrium has two reactants. If the concentration of the reactants are doubled, the equilibrium constant will

At $550 \mathrm{K}$, the ${\mathrm{K}}_{\mathrm{c}}$ for the following reaction is ${10}^4 {\mathrm{mol}}^{-1} \mathrm{L}, {\mathrm{X}}_{\left(\mathrm{g}\right)}+{\mathrm{Y}}_{\left(\mathrm{g}\right)}\rightleftharpoons {\mathrm{Z}}_{\left(\mathrm{g}\right)}$. At equilibrium, it was observed that $\left[\mathrm{X}\right]=\frac{1}{2}\left[\mathrm{Y}\right]=\frac{1}{2}\left[\mathrm{Z}\right]$ 

What is the value of $\left[\mathrm{Z}\right]$ (in $\mathrm{mol} {\mathrm{L}}^{-1}$) at equilibrium? 

If pressure is increased on the equilibrium

Ice$\rightleftharpoons$Water

Which of the following occurs?