A 100 L reaction container is charged with 0.612 mol of NOBr, which decomposes at a certain temperature** (say between 100 and 150 oC) according to the following reaction:

NOBr(g) ? NO(g) + 0.5Br2(g)

At equilibrium the bromine concentration is 2.12x10-3 M. Calculate Kc (in M0.5)

**Not specifying the temperature allows for a more liberal use of random numbers.

The value of the equilibrium constant is 0.024

Explanation:

Initial moles of   = 0.612 mole

Volume of container = 100 L

Initial concentration of  

equilibrium concentration of

Equilibrium constant is the ratio of the concentration of products to the concentration of reactants each term raised to its stochiometric coefficients.

The given balanced equilibrium reaction is,

at t=0       0       0

At eqm. conc.      x       x/2     

The expression for equilibrium constant for this reaction will be,

we are given : x/2 =

Now put all the given values in this expression, we get :

Thus the value of the equilibrium constant is 0.024