Question

the equilibrium constant of the decomposition of NOCL is 1.6*10^-5. calculatethe concentration of all species at equilibrium if initially 3.52 mol of NOCL is placed in a 5.00 L container

Answer 1

You don't say if that is Kc or Kp; however, since you listed a volume I assume it is kc. M NOCl = 3.52/5.00 = about 0.7M but you can do it closer than that.
............2NOCl ==> 2NO + Cl2
I............0.70......0......0
C............-2x.......2x.....x
E............0.70-2x...2x.....x
Substitute and solve.