What is the equilibrium concentrations of each substance in the system

Question

In a given experiment 3.4 moles of pure NOCl was placed in an otherwise empty 2.0 L container. Equilibrium was established given the following reaction:

2NOCl(g) 2NO(g) Cl2(g) K = 1.6 × 10-5

Answer 1

This should be in chemistry.

Use the RICE Method:

Reaction: 2 NOCl  -----> 2 NO plus Cl2

Initial:  1.4M (why?).....0.....0

Change: -X..... X.....X/2  (explanation: every time you lose one NOCl you make one NO + 1/2 Cl2)

Equilibrium: 1.4-X.....X.....X/2

Now use your definition of the equilibrium constant, and write in the values from the equilibrium line, expressed in terms of X as an unknown.

It looks as if you're heading for a cubic equation (Help!) but since K is small, you can assume that X is small compared with 1.4, and replace (1.4-X) by 1.4 on its own.

Notice that you cannot ignore the other X's (why not?)

Then all that remains is the arithmetic.  Over to you.  Good luck.