CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
For the reaction A(g) ⇌ 2 B(g) at 310K, a researcher records the instantaneous rates of the forward and reverse reactions every 50 s. A portion of the data is shown in the table.
Time (s) | Forward rate (molL−1s−1) | Reverse rate (molL−1s−1)
0 | 0.120 | 0.000
50 | 0.095 | 0.025
100 | 0.075 | 0.045
150 | 0.060 | 0.060
200 | 0.050 | 0.070
250 | 0.045 | 0.080
Use the data to answer the following.
(a) Determine the time at which the system is at equilibrium for the first time. Explain how you arrived at your answer using the numerical values provided.
(b) Calculate the net rate of formation of B(g) at t = 100 s. Include the appropriate sign in your answer and interpret its meaning with respect to the direction of net change.
(c) Between 150 s and 250 s, identify the interval during which products are being converted to reactants overall. Justify your choice quantitatively.
(d) If the researcher were to extend data collection to 500 s, predict the values (within ±0.005molL−1s−1) you would expect for both the forward and reverse rates at that time, and provide reasoning based on the experimental trend.