Consider the following hypothetical reaction mechanism A + 3B → 2C. The rate of appearance of C given by d[C]/dt may also be expressed as: A) d[C]/dt = d[A]/dt B) d[C]/dt = −(3/2) d[B]/dt C) d[C]/dt = −(2/3) d[B]/dt E) d[C]/dt = (2/3) d[B]/dt
Solution: When we are given an equation, we can write the rate expression in terms of appearance of products and disappearance of reactants.
The rate expression for the equation give would be:
Rate = -Δ[A] = -1 Δ[B] = 1 Δ[C]
Δt 3 Δt 2 Δt
Therefore -1 Δ[B] = 1 Δ[C]
3 Δt 2 Δt
Rate of appearance of C is Δ[C]/ Δt
Δ[C]/ Δt = -2/3Δ[B]/ Δt Choice C