CHEMISTRY · Single correct · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
For the reaction E ⇌ F in a sealed container, the rates of the forward and reverse reactions were measured at three different times.
Time (min): 0 5 10
Rate_forward (mol L⁻¹ min⁻¹): 4.0 2.0 1.5
Rate_reverse (mol L⁻¹ min⁻¹): 0.0 2.0 2.5
Which statement best describes the behavior of the system between 5 min and 10 min?
(a) Between 5 min and 10 min, the system remains at equilibrium because the forward and reverse rates stay essentially constant.
(b) E continues to convert to F overall between 5 min and 10 min because the forward rate, on average, is greater than the reverse rate.
(c) After reaching equilibrium at 5 min, the net change is conversion of F back to E because the reverse rate exceeds the forward rate throughout 5–10 min.
(d) The reaction stops completely after 5 min, so no further conversion between E and F occurs.