Question

Which of the following statement is incorrect for the reaction?
$H _{2}(g)+ Br _{2}(l) \longrightarrow 2 HBr (g); \Delta_{r} H^{\circ}=-178.3\, kJ\, mol ^{-1}$

• A. The enthalpy change given is equal to $\Delta_{f} H^{\circ} HBr$.
• B. $\Delta_{r} H^{\circ}=2 \Delta_{f} H^{\circ} HBr$
• C. $\Delta_{f} H^{\circ}$ of an element in refrence state is taken as zero
• D. None of the above

Answer 1

Answer: (A)

Statement (a) is incorrect.
It's correct form is as follows :
The enthalpy change given, i.e. $\Delta_{r} H^{\circ}=-178.3\, kJ / mol$ is not equal to $\Delta_{f} H^{\circ} HBr$ as here two moles, instead of one mole of the product is formed.
Rest other statements are correct.