Question

To determine the molarity of naoh solution, student took 3.5 g of khp (khp – potassium hydrogen phthalate; molar mass = 204.22 g/mol) and dissolved in 50 ml of water and titrated with the given unknown molarity naoh solution loaded in burette. his burette volume read 1.85 ml at the start of the experiment and 24.65 ml when the phenolphthalein indicator turned pink. using above experimental details, determine the molarity of naoh solution? (enter your answer in two decimal palaces).

Answer 1

Hello!

First, we need to determine the concentration of KHP. This concentration is:

$\frac{3,5g KHP }{50 mL sol}* \frac{1000 mL}{1 L}* \frac{1 mol KHP}{204,22 g KHP}=0,343 M$

The neutralization reaction is:

KHP + NaOH → NaKP + H₂O

At the equivalence point:

$moles NaOH=moles KHP \\ \\ cNaOH*vNaOH=cKHP*vKHP \\ \\ cNaOH= \frac{cKHP*vKHP}{vNAOH}= \frac{0,343M*50mL}{(24,65 mL-1,85 mL)} =0,75 M$

So, the concentration of NaOH is 0,75M

Have a nice day!