molarity of H2 = 0.25 / 10 = 0.025 M
molarity of F2 = 0.37 / 10 = 0.037 M
H2Â Â Â +Â Â Â Â Â F2
<-------------------------> 2HF
0.025Â Â
0.037Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
0Â Â Â Â Â --------------------->
initial
0.025-x    Â
0.037-x                           Â
2x  ------------------------> equilibrium
K = (2x)^2 / (0.025-x) (0.037-x)
81.0 = (2x)^2 / (0.025-x) (0.037-x)
81.0 = 4x^2 / (0.025-x) (0.037-x)
x =0.023
H2 concentration at equilibrium = 0.025-x = 0.025- 0.023
H2 concentration at equilibrium    =
0.002 M
