A closed 1.00 L vessel initially contains only gaseous reactants for the reversible…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A closed 1.00 L vessel initially contains only gaseous reactants for the reversible reaction
R(g) ⇌ P(g)
A kinetic study measures the instantaneous forward and reverse rates every 50 s. The results are summarized below.
Time / s
Rate_forward / (molL−1s−1)
Rate_reverse / (molL−1s−1)
0
1.20
0.10
50
0.90
0.25
100
0.60
0.45
150
0.32
0.30
200
0.28
0.28
Use the information provided to analyze how the direction of net change in the reaction evolves over time.
(1) For each recorded time, indicate whether there is a net conversion of R into P, a net conversion of P into R, or no net conversion. Support each answer with a brief comparison of the two rates.
(2) Estimate the time at which the system first attains equilibrium, explaining your reasoning with reference to the data.
(3) In molecular terms, account for the observed decrease in the forward rate and the simultaneous increase in the reverse rate between 0 s and 100 s.