Which of the following correctly represents reaction for estimating standard enthalpy of formation of HBr?

To estimate the standard enthalpy of formation of HBr, we consider the following reaction, which illustrates the formation of one mole of HBr from its elements in their standard states:

The balanced chemical equation is:

1. Balanced Chemical Reaction: $\frac{1}{2} \text{H}_2(g) + \frac{1}{2} \text{Br}_2(g) \rightarrow \text{HBr}(g)$

In this reaction:

• Hydrogen gas ($\text{H}_2$) is taken from its diatomic form.
• Bromine gas ($\text{Br}_2$) is also taken from its diatomic state.
• The product is hydrogen bromide ($\text{HBr}$), which is formed in the gaseous state.

Explanation:

• Standard State: The standard enthalpy of formation refers to the change in enthalpy when one mole of a compound is formed from its elements in their standard states (1 bar, 298.15 K).

Thus, the given reaction appropriately represents the standard enthalpy of formation for hydrogen bromide (HBr).