In: Chemistry
Find the equilibrium concentration of the Mn(C2O4)2− ion(in M) when 0.50 L of 0.030 M Mn(NO3)2 are mixed with 1.0 L of 1.2M Na2C2O4. Kf of Mn(C2O4)2 2- is 6.3 x 10 5.
moles Mn2+ = 0.03 M x 0.5 L = 0.015 mmol
moles C2O4^2- = 1.2 M x 1.0 L = 1.2 mmol
ICE chart
Mn2+ + 2C2O4^2- <===> [Mn(C2O4)2]^2-
I 0.015 1.2 -
C -x -2x +x
E 0.015-x 1.2-2x x
So,
Kf = [Mn(C2O4)2]2-/[Mn2+][C2O4^2-]^2
6.3 x 10^5 = x/(0.015-x)(1.2-2x)^2
1.44 - 4.8x + 4x^2
0.0216 - 0.072x + 0.06x^2 - 1.44x + 4.8x^2 - 4x^3
-4x^3 + 4.86x^2 - 1.512x + 0.0216
-2.52 x 10^6 x^3 + 3.062 x 10^6 x^2 - 9.52 x 10^5 x + 1.361 x 10^4 = 0
x = 0.015 mmol
So,
equilibrium concentration of [Mn(C2O4)2]^2- = 0.015 mmol/1.5 L = 0.01 M