Question

1) The equilibrium constant, K, for the following reaction is 1.29×10^-2 at 600 K.

COCl₂(g) <--- ---> CO(g) + Cl₂(g)

An equilibrium mixture of the three gases in a 1.00 L flask at 600 K contains  0.206 M  COCl₂, 5.16×10^-2 M CO and 5.16×10^-2M Cl₂. What will be the concentrations of the three gases once equilibrium has been reestablished, if 2.88×10^-2 mol of CO(g) is added to the flask?

[COCl2]	=	M
[CO]	=	M
[Cl2]	=	M

2) The equilibrium constant, K, for the following reaction is 1.80×10^-4 at 298 K.

NH₄HS(s) <--- ---> NH₃(g) + H₂S(g)

An equilibrium mixture of the solid and the two gases in a 1.00 L flask at 298 K contains  0.315 mol  NH₄HS,   1.34×10^-2 M NH₃ and 1.34×10^-2 M H₂S. If the concentration of H₂S(g) is suddenly increased to 2.12×10^-2 M, what will be the concentrations of the two gases once equilibrium has been reestablished?

[NH3]	=	M
[H2S]	=	M

Answer 1

COCl2(g) <--- ---> CO(g) + Cl2(g)

Q = [CO][Cl2]/[cocl2]

    = (0.0516*0.0516)/0.206

    = 0.01292

Q = K,system is at equilibrium.

          COCl2(g) <--- ---> CO(g) + Cl2(g)

initial 0.206 M            0.0516+0.0288 M 0.0516 M

change     +x                    - x           -x

equil     0.206+x M            0.0804-x       0.0516-x

K = ((0.0804-x)*(0.0516-x))/(0.206+x) = 0.0129

x = 0.01115

[COCl2] = 0.206+0.01115 = 0.21715 M

[CO]     = 0.0804-x = 0.0804-0.01115 = 0.06925   M
   

[Cl2]     = 0.0516-0.01115 = 0.04045 M

2)

   NH4HS(s) <--- ---> NH3(g) + H2S(g)

initial 0.315 M           0.0134 M 0.0134 M

after   0.315 M           0.0134 M 0.0212 M

change     +x               -x        -x

equilb   0.315+x M        0.0134-x   0.0212-x M

   K = [NH3][H2S]

    1.8*10^-4 = (0.0134-x)*(0.0212-x)

x = 0.00333 M

[NH3] = 0.0134-x = 0.0134-0.00333 = 0.01 M

[H2S]     = 0.0212-x = 0.0212-0.00333 = 0.01787 M