Question

The H-H bond energy is 430 kJ mol^-1 and Cl-Cl bond energy is 240 kJ mol^-1. Δ_fH for HCl is - 90 kJ, then H-Cl bond energy is ______.

पर्याय

• 213 kJ mol^-1

• 180 kJ mol^-1

• 360 kJ mol^-1

• 425 kJ mol^-1

Answer 1

The H-H bond energy is 430 kJ mol^-1 and Cl-Cl bond energy is 240 kJ mol^-1. Δ_fH for HCl is - 90 kJ, then H-Cl bond energy is 425 kJ mol^-1.

Explanation:

\[\ce{1/2 H_{2(g)} + 1/2 Cl_{2(g)} -> HCl_{(g)}}\]

`Delta_"f" "H"_"HCl" = [("B"."E". "of"  "H" - "H")/2 + ("B"."E". "of Cl - Cl")/2]` - [B.E. of H - Cl]

- 90 = `[430/2 + 240/2]`- [B.E. of H - Cl]

- 90 = 215 + 120 - [B.E. of H - Cl]

- 90 = 335 - [B.E. of H - Cl]

∴ B.E. of H - Cl = 335 + 90 = 425 kJ mol^-1.