Question

Calculate the molarity of the NaOH solution if 220 mL of NaOH was added to 430 mL of 2.10 M HNO2. The pH of the resulting solution was 1.40 units greater than the original acid solution. Show work.

Answer 1

HNO2 (aq) + NaOH (aq) <======> NaNO2 (aq) + H2O (aq)

from this balanced equation it is clear that one mole of HNO2 required one mole of NaNO2

no of moles HNO2 = Molarity of HNO2 x volume of HNO2

= 2.10 M x 0.43 L

= 0.903 mole

0.903 mol of HNO2 required 0.903 mol NaOH

now we have moles of NaOH volume of NaOH

Molarity = mol of NaOH / volume in liters

= 0.903 mol / 0.22 L

= 4.105 M

the fromed salt here is NaNO2 which is week acid salt it will also have some pH thats why pH is more than expected