First of all, we need to find the average rate if disappearence for A, where the formula is -ΔC/Δt
First rate (A) = -ΔC/Δt = – (0.430-0.720)/(196-0) = 1.48 * 10-3 mol/(L*s)
Second rate (A) = -Δc/Δt = – (0.140-0.430)/(392-196) = 1.48 * 10-3 mol/(L*s)
As we can see, the average rate of A equals 1.48 * 10-3 mol/(L*s)
Provided that A⟶2B,
The average rate of change (B) = 1.48 * 10-3 * 2 = 2.96 * 10-3 mol/(L*s)