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

ID: 692831 • Letter: 1

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?

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?

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

Explanation / Answer

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