ENCE 433 Dr. Alba Torrents

EXAMINATION 2 "SOLUTION" Fall 1996

Thursday, October 31

1.

2.

1. Alk = [Na⁺] = 10^-3
2. Alk = -[Cl^-] = -10^-3

Alk = [Na⁺] - [H₂PO₄^-] = 3 [Na₃PO₄] -1 [Na₃PO₄] = 2 [Na₃PO₄] = 2x10^-4.5

3.

(a)

1. pH of the mixture can be estimated using the Deffeyes diagram:

pH ~ 9.5 so we need to add a base.

At this pH most of C_T is as HCO₃^-, so we need to titrate it all to CO₃^-2; We need to add the same number of moles of an strong base.

4. (a)

the number of moles will depend on the desire molarity of the final solution. If X Molar

X = [Na₂CO₃] + [NaHCO₃]

(b) If equilibrated with the atmosphere, one can use just the salt as NaHCO₃ will be form by Na₂CO₃ + CO₂ NaHCO₃