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Physical Chemistry

What will be the pH of the resultant solution formed by titration of 50ml of 0.02 molar Na2Co3 with 100 ml of 0.0125 molar HCl. If pka1 and pka2 are 6.5 and 10.5 for h2 co3 respectively?

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Profile image of pragati singh
7 Years agoGrade
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1 Answer

Profile image of Arun
6 Years ago
The number of millimoles of sodium carbonate =25×0.4=10 millimoles.
The number of millimoles of HCl =50×0.025=1.25 millimoles.
Out of 10 millimoles of sodium carbonate, 1.25 millimoles will react with 1.25 millimoles of HCl to from 1.25 millimoles of sodium bicarbonate.
8.75 millimoles of sodium carbonate remain unreacted.
An acidic buffer solution is obtained in which acid is sodium bicarbonate and salt is sodium carbonate.
The expression for the pH of the solution is pH=pK 
a
​ 
 +log 
[acid]
[salt]
​ 
 =10.3+log 
1.25
8.75
​ 
 =11.14