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NEET levelSingle correct optionDifficulty 1 of 3td118

The $H - H$ bond enthalpy is $436 kJ mo l^{- 1}$ . What is $Δ H$ for $2 H (g) H X_{2} (g)$ ?

A $+ 436 kJ mo l^{- 1}$
B $+ 872 kJ mo l^{- 1}$
C $- 436 kJ mo l^{- 1}$
D $- 218 kJ mo l^{- 1}$

Answer: C

Breaking one mole of

H - H

bonds absorbs

436 kJ

. The reverse process, forming the bond from atoms, releases the same amount, so

Δ H = - 436 kJ mo l^{- 1}

.

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