28. The value of Kc for the reaction 2HI(g)H2(g)+I2(g) is 1×10-4. At a given time, the composition of reaction mixture is [HI]=2×10-5 mol, [H2]=1×10-5 mol and [I2]=1×10-5 mol. In which direction will the reaction proceed?


Given that,
[HI]=2×10-5 mol[H2]=1×10-5 mol[I2]=1×10-5 mol 
At a given time, the reaction quotient Q for the reaction will be given by the expression
Q=[H2][I2][HI]2=1×10-5×1×10-5(2×10-5)2=14=0.25=2.5×10-1
As the value of reaction quotient is greater than the value of Kc, i.e., 1×10-4 the reaction will proceed in the reverse reaction.