Question

For the reaction A+2B→C under a given set of conditions, the initial rate is 0.100 M/s.What is Δ[B]/Δt under the same conditions?

Answer 1

Answer: The rate of disappearance ( -Δ[B]/Δt) under the same conditions is 0.200 M/s.

Explanation:

$A+2B\rightarrow C$

Initial Rate of the reaction = 0.100 M/s

Rate of disappearance of B:

$-\frac{1}{2}\frac{\Delta [B]}{\Delta t}=0.100 M/s$

$-\frac{\Delta [B]}{\Delta t}=2\times 0.100 M/s=0.200 M/s$

The rate of disappearance ( -Δ[B]/Δt) under the same conditions is 0.200 M/s.

Answer 2

The rate of change of concentration of a reactant is equal to the initial rate multiplied by the stoichometric coefficient. Thus:
Δ[B]/Δt = 2 x 0.1
= -0.2 M/s (the negative sign is because B is a reactant.)