Question

An aqueous solution contains 0.216 M ascorbic acid (H2C6H6O6) and 0.131 M hydrochloric acid.

Calculate the ascorbate (C6H6O62-) ion concentration in this solution.

[C6H6O62-] =______________ mol/L.

Answer 1

Ascorbic acid = HAsc
.........HAsc ==> H^+ + Asc^-
initial.0.216.....0......0
change....-x.......x......x
equil..0.216-x.....x.......x

..........HCl ==>H^+ + Cl^-
initial...0.131..0......0
change...-0.131..0.131..0.131
equiol....0......0.131..0.131

Write the Ka expression for HAsc
K = (H^+)(Asc^-)/(HAsc)
For (H^+) substitute x + 0.131 (x from the HAsc equil + 0.131 from the HCl equil).
For (Asc^-) substitute x
For (HAsc) substitute 0.216-x
Solve for x.