Consider the reaction:
2 HBr (g) → H₂ (g) + Br₂ (g)
a. Express the rate of the reaction in terms of the change in concentration of each of the reactants and products.

Verified step by step guidance

1. Express the rate of the reaction in terms of the change in concentration of HBr. The rate of disappearance of HBr can be written as: \( -\frac{1}{2} \frac{\Delta [\text{HBr}]}{\Delta t} \).
2. Express the rate of the reaction in terms of the change in concentration of H₂. The rate of formation of H₂ can be written as: \( \frac{\Delta [\text{H}_2]}{\Delta t} \).
3. Express the rate of the reaction in terms of the change in concentration of Br₂. The rate of formation of Br₂ can be written as: \( \frac{\Delta [\text{Br}_2]}{\Delta t} \).
4. Since the stoichiometry of the reaction is 2:1:1 for HBr, H₂, and Br₂ respectively, the rate of disappearance of HBr is twice the rate of formation of H₂ and Br₂.
5. Therefore, the rate of the reaction can be expressed as: \( -\frac{1}{2} \frac{\Delta [\text{HBr}]}{\Delta t} = \frac{\Delta [\text{H}_2]}{\Delta t} = \frac{\Delta [\text{Br}_2]}{\Delta t} \).

Key Concepts

Reaction Rate

The reaction rate is a measure of how quickly reactants are converted into products in a chemical reaction. It is typically expressed as the change in concentration of a reactant or product over time. In this case, the rate can be defined in terms of the decrease in concentration of HBr and the increase in concentrations of H2 and Br2.

Stoichiometry

Stoichiometry involves the quantitative relationships between the amounts of reactants and products in a chemical reaction, based on the balanced chemical equation. For the given reaction, the coefficients indicate that two moles of HBr produce one mole of H2 and one mole of Br2, which is essential for expressing the rates in terms of their respective concentrations.

Concentration Change

Concentration change refers to the difference in the amount of a substance in a given volume over time. In the context of the reaction, it is important to express how the concentrations of HBr, H2, and Br2 change as the reaction progresses, which is crucial for calculating the rate of the reaction accurately.