Â
NO2 (g) +Â Â Â NO (g)Â Â Â Â Â
⇌     N2O (g) Â
+Â Â Â O2 (g)
Initial                   Â
0.056Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
0.294Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
 Â
0.184Â Â Â Â Â Â Â Â Â Â Â Â
0.377
at equilibrium       0.056
+x         Â
0.294
+x            Â
0.184-x        0.377-x
So,
equilibrium NO2 concentration = 0.056 +x
But given that equilibrium NO2 concentration = 0.118 M
Hence,
                 Â
0.056 +x = 0.118
                             Â
x = 0.062 M
Hence,
equilibrium concentrations are
[NO2] = 0.118 M
[NO] = 0.294 +x = 0.294 + 0.062 = 0.356 M
[N2O] = 0.184-x = 0.184 -0.062 = 0.122 M
[O2] = 0.377-x = 0.377-0.062 = 0.315 M
Therefore,
    Kc = [ N2O] [O2]/ [NO2] [NO]
          Â
= 0.122 x 0.315 / 0.118 x 0.356
           Â
= 0.912
Therefore,
   Kc = 0.912
