A concentration-versus-time graph for the system X(g) ⇌ Y(g) initially shows a stable…
CHEMISTRY · Subjective · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A concentration-versus-time graph for the system X(g) ⇌ Y(g) initially shows a stable plateau at [X] = 0.25 M and [Y] = 0.75 M. At t = 30 s, the curve for Y suddenly spikes to 1.20 M and then gradually falls to a new plateau of 0.85 M by t = 60 s; simultaneously, the curve for X dips to 0.15 M and then rises to a new plateau of 0.30 M. Which species was added to the system at t = 30 s, and what evidence from the graph supports your conclusion?