Question

Consider the reaction A(g)+12B(g)→2C(g).

A) Identify the expression for the rate of the reaction with respect to each of the reactants and products.

-rate=−Δ[A]Δt=−2Δ[B]Δt=12Δ[C]Δt

-rate=−1/2Δ[A]Δt=−2Δ[B]Δt=Δ[C]Δt

-rate=−2Δ[A]Δt=−Δ[B]Δt=12Δ[C]Δt

-rate=−2Δ[A]Δt=−1/2Δ[B]Δt=Δ[C]Δt

Answer 1

In the reaction A(g) + 1/2 B(g) → 2 C(g), the correct rate expressions take into account the stoichiometric coefficients, with the consumption of A and B being -Δ[A]/Δt and -2Δ[B]/Δt respectively, and the formation of C being (1/2)Δ[C]/Δt.

Step-by-step explanation:

When determining reaction rates in a chemical equation, it is essential to account for the stoichiometry of the reaction. For the given reaction A(g) + 1/2 B(g) → 2 C(g), the rates of consumption of the reactants A and B must reflect the stoichiometry. Therefore, when expressing these rates, we must include the stoichiometric coefficients in the rate expressions.

The correct rate expressions for this reaction are:

• Rate with respect to A: rate = -Δ[A]/Δt
• Rate with respect to B: rate = -2Δ[B]/Δt
• Rate with respect to C: rate = (1/2)Δ[C]/Δt

The negative sign indicates the consumption of reactants, while the positive sign indicates the formation of products. Since 2 molecules of C are produced for every molecule of A consumed, the rate of disappearance of A is half that of the appearance of C. Similarly, because B reacts in a 1:2 ratio with A, twice as much B is consumed for each unit of A, which explains the factor of 2 in the rate expression for B.