For the reversible reaction A(g)⇌B(g) carried out in a rigid container at constant temperature, the concentrations of A and B were recorded at 5-minute intervals:
Time (min) [A] (M) [B] (M)
5 0.40 0.10
10 0.25 0.25
15 0.20 0.30
20 0.20 0.30
At which recorded time is there first experimental evidence that the system has reached equilibrium?
a) 10 min
b) 5 min
c) 20 min
d) 15 min