From the following data at 25°C: 1/2 (g) + 1/2 (g) - OH(g); δ H° = 42 kJ; (g) + 1/2 (g) - (g); δ H° = -242 kJ; (g) - 2H(g); δ H° = 436 kJ; (g) - 2O(g); δ H° = 495 kJ. Which of the following statem

Question

From the following data at 25°C: 1/2 $H_2$(g) + 1/2 $O_2$(g) -> OH(g); δ H° = 42 kJ; $H_2$(g) + 1/2 $O_2$(g) -> $H_2O$(g); δ H° = -242 kJ; $H_2$(g) -> 2H(g); δ H° = 436 kJ; $O_2$(g) -> 2O(g); δ H° = 495 kJ. Which of the following statement(s) is/are correct?

Prashant Kotian · Accepted Answer

Correct answer: A,D. (a) δ H = 2*(218) + 247.5 - (-242) = 436 + 247.5 + 242 = 925.5 kJ. (Correct). (b) δ H(OH->H+O) = 218 + 247.5 - 42 = 423.5 kJ (not 502 kJ, incorrect). (c) delta_f H(H,g) = +218 kJ/mol, not -218 (incorrect). (d) Given directly from first reaction: delta_f H(OH,g) = 42 kJ/mol (correct).

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