A student monitors the rates of the forward and reverse reactions for a system at…
CHEMISTRY · Single correct · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A student monitors the rates of the forward and reverse reactions for a system at constant temperature and records the following data.
Time (s) Rate_forward (mol L⁻¹ s⁻¹) Rate_reverse (mol L⁻¹ s⁻¹)
0 0.80 0.00
40 0.35 0.22
80 0.24 0.24
120 0.22 0.25
160 0.22 0.26
Which of the following best describes how the concentrations of reactants and products are changing between 0 s and 80 s?
(a) Both reactant and product concentrations remain constant between 0 s and 80 s because the system has already reached equilibrium by 80 s.
(b) The concentration of reactants decreases while the concentration of products increases because the forward rate exceeds the reverse rate.
(c) The concentration of reactants increases while the concentration of products decreases because the reverse rate exceeds the forward rate between 0 s and 80 s.
(d) Both reactant and product concentrations decrease over this interval because the forward and reverse rates are each getting smaller with time.