The pH of blood stream is maintained by a proper balance of `H_(2)CO_(3)` and `NaHCO_(3)` concentration. What volume of 5 M `NaHCO_(3)` solution should be mixed with a 10 mL sample of blood which is 2 M in `H_(2)CO_(3)` in order to maintain its pH ?
`[pk_(a)" for "H_(2)CO_(3)=6.1][10^(1.3)=19.9]`

Options

A. 40 mL
B. 38 mL
C. 50 mL
D. 79 mL

Answer

D

Explanation

`pH=pK_(a)+log.((HCO_(3)^-))/((H_(2)CO_(3)))`
Let V mL of `NaHCO_(3)` is required moles of `H_(2)CO_(3)`
`=2xx0.01=0.02`
Let V mL of `NaHCO_(3)` is required moles of `Na_(2)CO_(3)`
`=5xxV=5V` ltBrgt `thereforepH=pKa+log((5V)/(0.02))`
7.4=6.1+log`((5V)/(0.02))` ltBrgt `rArr v=79ml`