A reaction C(g) ⇌ D(g) is observed for 10 min following mixing of pure C with no D present
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A reaction
C(g) ⇌ D(g)
is observed for 10 min following mixing of pure C with no D present. Instantaneous rate data are collected every minute.
Time / min
Rate_forward / (molL−1s−1)
Rate_reverse / (molL−1s−1)
0
1.45
0.00
1
1.12
0.18
2
0.91
0.34
3
0.74
0.49
4
0.60
0.58
5
0.53
0.62
6
0.49
0.60
7
0.46
0.55
8
0.45
0.45
9
0.45
0.43
10
0.46
0.42
Answer the following questions about the kinetic trends.
(1) On plain paper, sketch qualitative (not numerically precise) curves of the forward and reverse rates versus time for the 10-min interval. Clearly label both curves.
(2) Identify the minute at which the system is closest to equilibrium and explain how you arrived at your answer using the data or your sketch.
(3) Determine during which 1-min interval there is a net conversion of D into C, even though earlier intervals showed the opposite net change. Support your conclusion with numerical evidence.
(4) Discuss how the shapes of the curves illustrate the dynamic nature of chemical equilibrium rather than a cessation of molecular activity.