In: Other
We have the reaction
2 A(aq) +B(aq) + 3 C(aq) ? 2 D(aq) + 2 E(aq) + 3F(aq)
.
At 25oC, we start with a solution that is 0.977 M in
A(aq), 0.655 M in B(aq), and 0.911 M in C(aq). There is no D(aq),
E(aq), or F(aq) present. Equilibrium is established, and at
equilibrium, the concentration of C(aq) is 0.677 M. What is the
value of the equilibrium constant, K, for this reaction? What is
the value of ?Go for this reaction? For this reaction,
we have another experiment where we only start with D(aq), E(aq),
and F(aq). At equilibrium, the concentrations of D(aq), E(aq), and
F(aq) are, respectively, 0.211 M, 0.322 M, and 0.255 M. What is the
concentration of B(aq) at equilibrium? The temperature is still
25oC.
The balanced reaction with ICE TABLE
2 A(aq) +B(aq) + 3 C(aq) = 2 D(aq) + 2 E(aq) + 3F(aq)
I 0.977 0.655 0.911
C (-2x) (-x) (-3x) +2x +2x +3x
E (0.977-2x) (0.655-x) (0.911-3x) +2x +2x +3x
At equilibrium
concentration of C(aq) = 0.677 M
0.911-3x = 0.677
x = 0.078
Concentration of A = 0.977-2x = 0.977 - 2*0.078 = 0.821 M
Concentration of B = 0.655-x = 0.655 - 0.078 = 0.577 M
Concentration of D = concentration of E = 2*0.078 = 0.156 M
Concentration of F = 3*0.078 = 0.234 M
Equilibrium constant expression of the reaction
Kc = [F]3[E]2[D]2 / [C]3[B] [A]2
= (0.234)3(0.156)4 / (0.078)3(0.577)(0.821)2
= 0.0411
G°= - RT ln K
= - 8.314 J/mol·K x (25+273)K x ln (0.0411)
= 7907.78 J
If start with only D
At equilibrium
Kc = [F]3[E]2[D]2 / [C]3[B] [A]2
= (0.255)3(0.322)2(0.211)2 / (-3x)3(-x)(-2x)2
0.0411 = (7.654 x 10^-5) / 108x6
108x6 = 0.00186
x = 0.161
concentration of B(aq) at equilibrium = x = 0.161 M