Question

which of the following reactions will get affected by increase in pressure ? Also mention whether the change will cause the reaction to go the right or left direction.
(i) `CH_(4)(g)+2S)_(2) (g) hArr CS_(2) (g) + 2H_(2)S(g)`
(ii) `CO_(2) (g) +C(s) hArr 2CO (g)`
(iii) `4NH_(3)(g) +5O_(2)(g) hArr 4NO (g) + 6H_(2)O(g)`
(iv) `C_(2)H_(4)(g) +H_(2)(g) hArr C_(2)H_(6) (g)`
(v) `COCI_(2)(g) hArr CO(g) +CI_(2)(g)`
(vi) `CaCO_(3)(g) hArr CaO(s)+CO_(2)(g)`

Answer 1

Only those reactions will be affected by increasing the pressure in which the number of moles of the gaseous reactants and products are different `(n_(p) ne n_(r))` (gaseous). With the exception of the reaction (1),all the remaining five reactions will get affected by increasing the pressure . In general.
the reaction will go to the left if `n_(p) gt n_(r)`
The reaction will go to the right if `n_(p) lt n_(r)`
Keeping this in mind.
(i) Increases in pressure will not affect equilibrium because `n_(p) =n_(r) =3.`
(ii) Increase in pressure will favour backward reaction because `n_(p)(2) gt n_(r) (1)`
(iii) Increase in pressure will favour backward reaction because `n_(p) (10) gt n_(r) (9)`
(iv) Increase in pressure will favour forward reaction because`n_(p)(1) lt n_(r) (2)`
(v) Increase in pressure will favour backward reaction because `n_(p) (2) gt n_(r)(1)`
(vi) Increase in pressure will favour backward reaction because `n_(p) (1) gt n_(r) (0)`