My professor in class literally didn't know how to do these equations that we are expected to know, and then moved on. I'm stuck. Any tips on how to do mass and charge balancing would be great. Here's a question in example:
Q: Choose the correct and full set of mass balance equation(s) for a solution prepared by mixing equal volumes of 0.050 M sodium oxalate, Na2C2O4 (aq), and 0.010 M ammonium chloride, NH4Cl (aq).
(a) 0.005 M = [NH4+] + [NH3]
(b) 0.010 M = [NH4+] + [NH3]
(c) 0.020 M = [NH4+] + [NH3]
(d) 0.025 M = [HC2O4–] + [C2O42–]
(e) 0.025 M = [H2C2O4] + [HC2O4–] + [C2O42–]
(f) 0.050 M = [HC2O4–] + [C2O42–]
(g) 0.050 M = [H2C2O4] + [HC2O4–] + [C2O42–]
(h) 0.025 M = [Na+]
(i) 0.050 M = [Na+]
(j) 0.005 M = [Cl–]
(k) 0.010 M = [Cl–]
I chose b, g and k because of course due to the molarity above, [Cl-] would be = 0.010M, so would [NH4+], and [C2O42-] would disassociate into [H2C2O4], [HC2O4-] and [C2O4 2-], and altogether the concentration would be 0.050M from the original question.
It's not in the question, but would [Na+] = 0.10M?
Charge Balancing:
Q:Choose the correct charge balance equation(s) for a solution prepared by mixing equal volumes of 0.050 M Na2C2O4 (aq), and 0.010 M NH4Cl (aq), without making any assumptions about pH.
(a) [NH4+] + [NH3] = [H2C2O4] + [HC2O4–] + [C2O42–]
(b) [NH4+] + [NH3] = [H2C2O4] + [HC2O4–] + 2[C2O42–]
(c) [NH4+] + [H3O+] = [HC2O4–] + [C2O42–] + [OH–]
(d) [NH4+] + [H3O+] = [HC2O4–] + 2[C2O42–] + [OH–]
(e) [NH4+] + [Na+] + [H3O+] = [HC2O4–] + [C2O42–] + [Cl–] + [OH–]
(f) [NH4+] + [Na+] + [H3O+] = [HC2O4–] + 2[C2O42–] + [Cl–] + [OH–]
I chose f as I believe that [C2O4 2-] disassociation would make 2[C2O4 2-] in the product and [HC2O4-] but not [H2C2O4] (that'd be cancelled out).
Does that make sense? How would one calculate the coefficients for OH- and H30+? I know in the multiple choices none of them have coefficients but in the future when I was doing the equilibriums there seemed to be more than one OH-.