A student continuously measures the pressure of each species in a sealed reaction…
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 continuously measures the pressure of each species in a sealed reaction mixture at 25 °C. Between 0 s and 250 s, the pressures change markedly; from 250 s to 600 s, the readings fluctuate randomly by less than 2 % around constant average values. Which conclusion is best supported by these observations?
(a) All chemical change has ceased after 250 s because the constant pressures show no further reaction.
(b) The forward and reverse reactions continue at equal rates, indicating a dynamic equilibrium after roughly 250 s.
(c) The slight pressure fluctuations after 250 s are most likely due to a small leak in the apparatus rather than a chemical process.
(d) After 250 s the forward reaction has gone to completion, so the system is now converting products back to reactants only.