Question

For the reaction H₂ + I₂ ⇌ 2HI, ∆H = 12.40 Kcal the heat of formation of HI is ……

(a) 12.4 Kcal mol^-1 

(b) -12.4 Kcal mol^-1 

(c) -6.20 Kcal mol^-1 

(d) 6.20 Kcal mol^-1

Answer 1

(d) 6.20 Kcal mol^-1

H₂ + I₂ → 2HI ∆H = 12.40K.cal

1/2 H + 1/2 I → HI = ∆H / 2

∴ 12.40 / 2 = 6.20 K.cal mol^-1 .