The role of a catalyst in a reversible reaction is to

The reaction $3O_2 \rightleftharpoons 2O_3; \Delta H = 69 \ kcal$ is favoured by..........

$N_2$ and $O_2$ combine to form nitric oxide as follows: ${N_2}_{(g)} + {O_2}_{(g)} \rightleftharpoons 2NO - \text{heat}$. Which of the following conditions will favor the production of $NO$?

For the reaction $SO_{2(g)} + 1/2 O_{2(g)} \rightleftharpoons SO_{3(g)}$,the percentage yield of product at different pressures is shown in the figure. Then,which among the following is true?

Does the number of moles of reaction products increase,decrease,or remain the same when each of the following equilibria is subjected to a decrease in pressure by increasing the volume?
$(a) \quad PCl_{5(g)} \longleftrightarrow PCl_{3(g)} + Cl_{2(g)}$
$(b) \quad CaO_{(s)} + CO_{2(g)} \longleftrightarrow CaCO_{3(s)}$
$(c) \quad 3Fe_{(s)} + 4H_2O_{(g)} \longleftrightarrow Fe_3O_{4(s)} + 4H_{2(g)}$

In the reaction $A_{(g)} + 2B_{(g)} \rightleftharpoons C_{(g)} + Q \ kJ$,greater product will be obtained or the forward reaction is favoured by: