The chemical equilibrium of a reversible reaction is not influenced by

The reaction $SO_2 + Cl_2 \rightleftharpoons SO_2Cl_2$ is exothermic. If some $SO_2$ is added to the equilibrium mixture at constant volume,then ...........

Explain the effect of adding $(i)$ Oxalic acid $(H_2C_2O_4)$,$(ii)$ $HgCl_2$,and $(iii)$ Potassium thiocyanate $(KSCN)$ on the equilibrium reaction: $Fe^{3+}(aq) + SCN^-(aq) \rightleftharpoons [Fe(SCN)]^{2+}(aq)$ (deep red color).

Explain the effect of temperature change on chemical equilibrium with an example.

For the equilibrium $2NO_{2(g)} \rightleftharpoons N_2O_{4(g)} + 21.9 \ kcal$,an increase in temperature will:

Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per the following endothermic reaction:
$CH_{4(g)} + H_2O_{(g)} \rightleftharpoons CO_{(g)} + 3H_{2(g)}$
$(a)$ Write an expression for $K_p$ for the above reaction.
$(b)$ How will the values of $K_p$ and the composition of the equilibrium mixture be affected by:
$(i)$ increasing the pressure
$(ii)$ increasing the temperature
$(iii)$ using a catalyst?