Which of the following reactions will get affected by increasing the pressure? Also, mention whether change will cause the reaction to go into forward or backward direction.(i) COCl2 (g) ⇌CO (g) + Cl2 (g)(ii) CH4 (g) + 2S2 (g) ⇌CS2 (g) + 2H2S (g)(iii) CO2 (g) + C (s) ⇌ 2CO (g)(iv) 2H2 (g) + CO (g) ⇌ CH3OH (g)(v) CaCO3 (s) ⇌CaO (s) + CO2 (g)(vi) 4 NH3 (g) + 5O2 (g) ⇌ 4NO (g) + 6H2O(g)

According to Le Chatelier’s principle, an increase in pressure applied to the system at equilibrium favours the reaction in the direction which takes place with a decrease in a total number of moles. If there is no change in the number of moles of gases in a reaction, a pressure change does not affect the equilibrium.

Hence, reactions affected will be those in which number of moles of products (np) is not equal to number of moles of reactants (np )

np ≠ nr. Hence, the reactions (i), (iii), (iv), (v) and (vi) will be affected. By applying Le Chatelier’s principle, we can predict the direction. In general,

The reaction will go to the left if np > nr

The reaction will go tp the right if np < nr

(i)COCl2 (g) CO (g) + Cl2 (g)

Number of moles of products (np)= 2

Number of moles of reactants (nr) = 1

np > nr

According to Le Chatelier’s principle, the reaction will proceed in the backward reaction.

(ii) CH4 (g) + 2S2 (g) CS2 (g) + 2H2S (g)

Number of moles of products (np)= 3

Number of moles of reactants (nr) = 3

np = nr

According to Le Chatelier’s principle, the reaction will not be affected by the pressure.

(iii) CO2 (g) + C (s) 2CO (g)

Number of moles of products (np)= 2

Number of moles of reactants (nr) = 1

np > nr

According to Le Chatelier’s principle, the reaction will proceed in the backward direction.

(iv) 2H2 (g) + CO (g) CH3OH (g)

Number of moles of products (np)= 1

Number of moles of reactants (nr) = 3

np < nr

According to Le Chatelier’s principle, the reaction will proceed in the forward direction.

(v) CaCO3 (s) CaO (s) + CO2 (g)

Number of moles of products (np)= 2

Number of moles of reactants (nr) = 1

np > nr

According to Le Chatelier’s principle, the reaction will proceed in the backward direction.

(vi) 4 NH3 (g) + 5O2 (g) 4NO (g) + 6H2O(g)

Number of moles of products (np)= 10

Number of moles of reactants (nr) = 9

np > nr

According to Le Chatelier’s principle, the reaction will proceed in the backward direction.

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