Question

For the standardization of their sodium hydroxide solution a pair of students weighed out 0.5342 g of KHP (MM 204.22 g/mol). They found that it took 21.36 mL of their NaOH solution to reach the endpoint. What is the concentration of their NaOH solution?

Answer 1

The concentration of their NaOH solution is 0.1225 M.

Step-by-step explanation:

Moles of KHP :

Given, Mass of KHP = 0.5342 g

Molar mass of KHP = 204.22 g/mol

The formula for the calculation of moles is shown below:

`moles = (Mass\ taken)/(Molar\ mass)`

Thus,

`Moles= (0.5342\ g)/(204.22\ g/mol)`

`Moles\= 2.6158* 10^(-3)\ mol`

According to the reaction shown below:

KHP + NaOH ⇒ KNaP + H₂O

1 mole of KHP reacts with 1 mole of NaOH

So,

`2.6158* 10^(-3)\ mol` of KHP reacts with
`2.6158* 10^(-3)\ mol` of NaOH

Moles of NaOH =
`2.6158* 10^(-3)\ mol`

Volume = 21.36 mL = 0.02136 L ( 1 mL = 0.001 L)

The expression for molarity is:-

`Molarity=(Moles\ of\ solute)/(Volume\ of\ the\ solution)`

`Molarity_(NaOH)=(2.6158* 10^(-3))/(0.02136)`

`Molarity_(NaOH)=0.1225\ M`

The concentration of their NaOH solution is 0.1225 M.