The value of ΔH° for the reaction Cu⁺(g) + I⁻(g) → CuI(g) is − 446 kJ mol⁻¹. If the ionization energy of Cu(g) is 745 kJ mol⁻¹ and the electron affinity of I(g) is − 295 kJ mol⁻¹, then the value of ΔH

Question

The value of ΔH° for the reaction Cu⁺(g) + I⁻(g) → CuI(g) is − 446 kJ mol⁻¹. If the ionization energy of Cu(g) is 745 kJ mol⁻¹ and the electron affinity of I(g) is − 295 kJ mol⁻¹, then the value of ΔH° for the formation of one mole of CuI(g) from Cu(g) and I(g) is -

Accepted Answer

Answer: 4 kJ — Cu → Cu⁺ + e⁻ ΔH = +745 I + e⁻ → I⁻ ΔH = −295 Cu⁺ + I⁻ → CuI ΔH = −446 Total: ΔH = 745 − 295 − 446 = +4 kJ mol⁻¹

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