The gas-phase equilibrium has at a certain temperature

CHEMISTRY · Single correct · AP · Chemistry · Equilibrium · Equilibrium

Problem

The gas-phase equilibrium

2\,\mathrm{SO_2}(g)+\mathrm{O_2}(g)\;\rightleftharpoons\;2\,\mathrm{SO_3}(g)

has

K_c = 5.0

at a certain temperature. A 1.0 L reaction vessel initially contains the equilibrium mixture shown in the table below.

t = 0

an additional

0.20\,\text{mol}

of SO

_2

is injected into the vessel. Concentrations are then monitored for several minutes:

Time (min)	[SO $_2$ ]	[O $_2$ ]	[SO $_3$ ]
0 $^{+}$	0.70	0.20	0.50
1	0.60	0.17	0.58
2	0.55	0.15	0.62
3	0.53	0.14	0.64

At which listed time does the reaction first overshoot equilibrium so that

Q_c

exceeds

K_c

? (a) 0 min (immediately after injection) (b) 2 min (c) 1 min (d) 3 min