Concentration time data were collected for the following reaction at 30 oc
a + b --> 2c
concentration time data at t = 30oc
time (s) [a] (mol l-1)
0 0.65
15 0.52
30 0.35
45 0.28
60 0.22
75 0.14
90 0.095
(i) calculate the average rate of consumption of a in the first 15 seconds of reaction.
(ii) calculate the average rate of production of c in the first 15 seconds of reaction.
(iii) calculate the average rate of consumption of a in the last 15 seconds of the reaction.
(iv) explain the difference between the rates of consumption calculated in (i) and that in (iii)

(i) Calculate the average rate of consumption of A in the first 15 seconds of reaction: -8.67X10^(-3) M/s

(ii) Calculate the average rate of production of C in the first 15 seconds of reaction: 0.0.17 M/s

(iii) Calculate the average rate of consumption of A in the last 15 seconds of the reaction: -3x10^(-3) M/s

(iv) Explain the difference between the rates of consumption calculated in (i) and that in (iii): At the beginning the reaction, is fast, then, when time passes, the reaction slows because there are less concentration of the reactants to produce C, so the rate is less.

Explanation:

The general formula to calculate any reaction rate is:

With this formula we can make the calculations, and we can know if r is positive or negative by knowing if we are calculating for a reactant or a product, positive for products, negative for reactants.

(i)

(ii)

In this case we need to multiply delta by 2, because 1 mole of A produces 2 moles of C:

As we know it is a product, r needs to be positive, so we change the sign of the result and we have: 0.017 M/s

(iii)

(iv)

Is already answered in the upper part.