Another equilibrium problem help? Medal and fan, multiple choice At a certain temperature, the equilibrium constant for the reaction of NO with Cl2 is 6250. If the initial concentration of NOCl is 1.0 M and that of NO is .10 M, what is the concentration of Cl2 at equilibrium? 2NO(g) + Cl2(g) 2NOCl A. .016 M B. .062 M C. .0016 M D. 1.0 M Thanks(:

Question

Another equilibrium problem help? Medal and fan, multiple choice

At a certain temperature, the equilibrium constant for the reaction of NO with Cl2 is 6250. If the initial concentration of NOCl is 1.0 M and that of NO is .10 M, what is the concentration of Cl2 at equilibrium?
2NO(g) + Cl2(g) <-> 2NOCl

A. .016 M
B. .062 M
C. .0016 M
D. 1.0 M

Thanks(:

matt101 · Answer

Start with your ICE chart. We now the reaction needs to move to the reactant side since there is no Cl2 initially

          2NO(g) + Cl2(g) <-> 2NOCl
I           0.10       0 M              1.0
C          +2x        +x              -2x
E      0.10+2x       x             1.0-2x

Using the Keq equation:

$$6250=\frac{ (1-2x)^2 }{ x(0.1+2x)^2 }$$

However, because the Keq is so much larger than the starting concentrations, the reverse reaction will not proceed very far, and so the changes in NO and NOCl concentration will be negligible. This will simplify the Keq equation.

$$6250=\frac{ (1)^2 }{ x(0.1)^2 }$$$$x=0.016$$
The answer is A!

anonymous · Answer

I know why I was stuck now. I wasn't concentrating on both the coefficients and I had forgotten about x being equal to O when K is much larger than Q.  Thankyou so much!(: