Question

If bond enthalpies of Cl—Cl bond, H—H bond and H—Cl bond are 243, 435 and 431 kJ mol ⁻¹ respectively, then calculate the ∆_fH° in kJ mol⁻¹ of HCl.

(a) − 184 

(b) − 92

(c) 170 

(d) − 88

Answer 1

Correct option is (b) − 92

The moles of HCl(g) are formed from its element, hence