A typical vitamin C tablet (containing pure ascorbic

Answered question

2022-04-13

A typical vitamin C tablet (containing pure ascorbic acid, H2C6H6O6) weighs 500. mg. One vitamin C tablet is dissolved in enough water to make 200.0 mL of solution. calculate the pH of this solution. Ascorbic acid is a diprotic acid.

Answer & Explanation

star233

star233

Skilled2022-06-20Added 403 answers

Given that 500. mg of Ascorbic acid ( C6H6O6H2) is dissolved in water to make 200.0mL
solution.
Molarity of ascorbic acid==Mass of ascorbic acid (g)Molar mass of ascorbic acid (g/mol)×1000

=0.5g176.13 g/mol×1000200mL

=0.014M

C6H6O6H2(aq)+H2O(!)   C6H6)O6H-(aq)+H3O*(aq)     Ka1=7.9×10-5

Initial: 0.014M 0 0

Change: -x x x
Equilibrium: 0.014-x x x

Ka1=[C6H6O6H-][H3O+][C6H6O6H2]

7.9×10-5=x×x0.014-x

(0.014-x) can be taken as 0.014

x=1.051×10-3

C6H6O6H-(aq)+H2O(l)     C6H6O62-(aq)+H3O+(aq)    Ka2=1.6×10-12

Initial: 1.051×10-3m0    1.051×10-3M

Change: -y y y

Equilibrium: (1.051×10-3-y)

Ka2=(1.051×10-3+y)×y1.051×10-3-y

1.6×10-12=1.051×10-3×y1.051×10-3

y=1.6×10-12M

[H+] of the solution= x+y

=(1.051×10-3 M) + (1.6×10-12 M)

=1.05116×10-3 M

pH = -log[H+]

= -log (1.05116×10-3 M)

= 2.97 3.0

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