Question

The bond energy of an $O-H$ bond is $109$ kcal/mol. When $1$ mole of water is formed, heat involved in kilocalories is:

• A. $-218$
• B. $-109$
• C. $+218$
• D. $+109$

Answer 1

The correct option is A $-218$

$H_{2}O$ has $2$ $O-H$ bonds.

Given that the bond energy of a $O-H$ bond is $109$ kcal/mol.

When one mole of water is formed, energy will be released.

Therefore, the heat released $=-109\times 2$ $=-218$ kcal per one mole of water formed.