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Question

1. Rate of Reaction:

For the reaction A→ B:

 

Time (sec)     [A] in mol/L 

0.0             2.25

3.0             0.95

6.0             0.52

9.0             0.38

12.0            0.27

15.0            0.18

a) Sketch a graph of [A] vs. time

(use graph paper or a suitable digital matrix to make a reasonable looking graph)

i. Identify the dependent and independent variables

Ii. determine the average rate of change over the first 9 seconds.

b) Describe the relationship between the instantaneous rate of reaction at the start of the reaction (initial rate) vs towards the end of the reaction? 

Answer 1

a). I can't very easily sketch the graph on this platform, but it should be easy if you just plot time on the x-axis and concentration on the y-axis.

i). The independent variable is time and dependent variable is [A].

ii). Average rate over the first 9 seconds = 2.25 - 0.38 / 9 = 0.208 mol/Lsec

b). The instantaneous rate is faster than the rate towards the end of the reaction. In the first 3 seconds, the initial rate = 1.93 mol/Lsec and at the end of the reaction (the last 3 seconds), the rate is 0.21 mol/Lsec.