Question

1:

a) Write the equilibrium expression for the following:

2 NOCl (g) = 2 NO (g) + Cl2 (g)

b) In the reaction above, the equilibrium concentration of NOCl = [0.0610], NO=[0.0151], Cl2= [0.0142], what is the equilibrium constant?

c) The initial concentration of NO2 in a closed container is 0.750 M. At equilibrium, the concentration of O2 is 0.125 M. What are the concentrations of NO2 and NO at equilibrium?

2 NO2 (aq) = 2 NO (aq) + O2 (aq)

Answer 1

Q1.

a)

Equilibrium Expression is defined by

Keq = [products]^p /[reactnats]^r

where p/r are their coefficients

so

Keq = [NO]^2[Cl2]/([NOCl]^2)

b)

if, in equilibrium we know that

NOCl = [0.0610],

NO=[0.0151],

Cl2= [0.0142]

then

Keq = (0.0151^2)(0.0142) / (0.0610^2)

Keq = 0.0008701

c)

if initially:

[NO2] = 0.75 M

[NO] = 0

[O2] = 0

find equilibrium concentrations

[NO2] = 0.75 -2x

[NO] = 0 +2x

[O2] = 0 + x

where x is the extent of reaction

AND we know that, [O2] = 0.125

so

[O2] = 0 + x = 0.125

then, x =0.125

[NO2] = 0.75 -2*0.125 = 0.50 M

[NO] = 0 +2*0.125 = 0.250 M