Question

A) An aqueous solution contains 0.376 M KHCO₃ and 0.224 M H₂CO₃.

The pH of this solution is____

B) An aqueous solution contains 0.183 M KHCO₃ and 0.300 M H₂CO₃.

The pH of this solution is ______

C) An aqueous solution contains 0.313 M NaHCO₃ and 7.12×10^-2 M H₂CO₃.

The pH of this solution is _________

Answer 1

Solution :-

Using the Henderson Hassel Balch equation we can find the pH of the buffer solution.

HCO3^- and H2CO3 makes the buffer solution.

pKa of the H2CO3 is 6.35

part a) solution containing 0.376 M KHCO3 and 0.224 M H2CO3

pH= pka + log [base]/[acid]

pH= 6.35+ log [HCO3^-]/[H2CO3]

pH= 6.35 + log [0.376]/[0.224]

pH= 6.57

part b) solution containing 0.183 M KHCO3 and 0.300 M H2CO3

pH= pka + log [base]/[acid]

pH= 6.35+ log [HCO3^-]/[H2CO3]

pH= 6.35 + log [0.183]/[0.300]

pH= 6.14

part c) solution containing 0.313 M NaHCO3 and 7.12*10^-2 M H2CO3

pH= pka + log [base]/[acid]

pH= 6.35+ log [HCO3^-]/[H2CO3]

pH= 6.35 + log [0.313]/[0.0712]

pH= 6.99