Question

Which reaction do you predict would have a positive (+) value for entropy (  S)?

		CO2 (s) → CO2 (g)
		H2O (l) → H2O (s)
		H2 (g) + Cl2 (g) → 2 HCl (g)
		N2 (g) + 3 H2 (g) → 2 NH3 (g)
		Ag+ (aq) + Cl- (aq) → AgCl (s)

Answer 1

Sol :-

Entropy (S) is the property of the system which measure the degree of ranodomness. The increases order of entropy is :

Solids < Liquids < Aqueous < Gases.

So,

(a). CO2 (s) --------------> CO2 (g), ΔS = +ve, because 1 mol of solid converted into 1 mol of gas.

(b). H₂O (l) --------------> H₂O (s), ΔS = -ve, because 1 mol of liquid converted into 1 mol of solid.

(c). H₂ (g) + Cl₂ (g) --------------> 2HCl (g) ,  ΔS = 0 (approx), because 2 mol of gaese converted into 2 mol of gases.

(d). N₂ (g) + 3H₂ (g) --------------> 2NH (g) , ΔS = -ve,, because 4 mol of gaese converted into 2 mol of gases.

(e). Ag⁺ (aq) + Cl^- (aq) --------------> AgCl (s), ΔS = -ve,, because 2mol of aqueous converted into 1 mol of solid.

Hence, option (a) is the correct answer.