JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Chemical Thermodynamics

Enthalpies of formation of

CCl_{4} (g), H_{2} O (g), CO_{2} (g)

and

HCl (g)

are

- 105, - 242, - 394

and

- 92 kJ mol^{- 1}

respectively. The magnitude of enthalpy of the reaction given below is ____

kJ mol^{- 1}

(nearest integer)

CCl_{4} (g) + 2 H_{2} O (g) \to CO_{2} (g) + 4 HCl (g)

Answer: 173

Solution

The reaction enthalpy is the sum of the formation enthalpies of the products minus that of the reactants,

Δ_{r} H = [Δ_{f} H (C O_{2}) + 4 Δ_{f} H (HCl)] - [Δ_{f} H (CC l_{4}) + 2 Δ_{f} H (H_{2} O)]

. Substituting,

Δ_{r} H = [(- 394) + 4 (- 92)] - [(- 105) + 2 (- 242)] = (- 762) - (- 589) = - 173 kJ mo l^{- 1}

. The magnitude of the enthalpy of the reaction is

173 kJ mo l^{- 1}

JEE Main · 2023 · 31 Jan 2023 · Shift 2 · Integer answer