Calculate the pH during the titration of 20.00 mL of 0.1000 M HNO2(aq) with 0.1000 M KOH(aq) after 13.27 mL of the base have been added. Ka of nitrous acid = 7.1 x 10-4.

pH = 2.462.

Explanation:

Hello there!

In this case, according to the reaction between nitrous acid and potassium hydroxide:

It is possible to compute the moles of each reactant given their concentrations and volumes:

Thus, the resulting moles of nitrous acid after the reaction are:

So the resulting concentration considering the final volume (20.00mL+13.27mL) is:

In such a way, we can write the ionization of this weak acid to obtain:

So we can set up its equilibrium expression to obtain x as the concentration of H3O+:

Next, by solving for the two roots of x, we get:

Whereas the correct value is 0.003451 M. Finally, we compute the resulting pH:

Best regards!

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