Question

For the following aqueous solutions, (i) write all pertinent equilibria, (ii) write

mass balance equation(s) and (iii) a charge balance equation.

a. 0.10 M solution of NaHCO3 (bicarbonate ion hydrolyzes to form CO3

2-)

b. 0.2 M HF

c. 0.35 M NH3

d. 0.0500 M in HClO2 and 0.100 M in NaClO2.

Answer 1

a. NaHCO3 + H2O = Na+ + HCO3^- (100%ionization)

HCO3^- + H2O = CO3^2- + H3O^+

Ka = [CO3^2-]*[H3O^+]/[HCO3^-]*[H2O]

b. HF = H^+ + F^-

The form and validity of each equilibrium constant are unaffected by the other

equilibria.

a. This doesn't mean that concentrations won't change when new species are

added/subtracted.

b. This means the algebraic expression of "Keq" is the same.

2. To calculate the concentration of the species in these multiple equilibria, you muste generate a number of independent algebraic expressions equal to (or greater than) the number of species present. Then you must solve the set of algebraic expressionss simultaneously.