Question

In a titration of nitrous acid with NaOH, the pH of the solution is 3.14 when the moles of HNO2 and the moles of NO2-- are equal. What is the Ka of nitrous acid?

Answer 1

`Ka=3.98x10^(-4)`

Step-by-step explanation:

Hello there!

In this case, since the modelling of titration problems can be approached via the Henderson-Hasselbach equation to set up a relationship between pH, pKa and the concentration of the acid and its conjugate base, we can write:

`pH=pKa+log(([NO_2^-])/([HNO_2]) )`

Whereas the pH is given as 3.14 and the concentrations are the same, that is why the pH would be equal to the pKa as the logarithm gets 0 (log(1)=0); thus, we can calculate the Ka via:

`Ka=10^(-pKa)=10^(-3.14)\\\\Ka=3.98x10^(-4)`

Best regards!