Question

What is the molarity of a NaOH solution if 26.55 ml are needed to titrate a 0.6939 g sample of KHP?

Answer 1

Hint: KHP means potassium hydrogen phthalate. The molecular formula of potassium hydrogen phthalate (KHP) is \[{{C}_{6}}{{H}_{4}}(CO_{2}^{-}{{K}^{+}})(C{{O}_{2}}H)\] . KHP is acidic in nature and will react with a base like sodium hydroxide.

Complete answer:
- In the question it is asked to calculate the molarity or concentration of 26.55 ml sodium hydroxide solution needed to titrate 0.6939 g of KHP.
- First we have to calculate the number of moles of KHP by taking the number of grams of the KHP and the molecular weight of the KHP.
- To calculate the number moles of KHP we need the molecular weight of the KHP.
- The molecular weight of the KHP is 204.22 g/mol.
- Number of moles of KHP can be calculated as follows.
Number of moles KHP = $\dfrac{0.6939}{204.22}=3.398\times {{10}^{-3}}mol$
- By using the number of moles of KHP we can calculate the concentration of the 26.55 ml of the sodium hydroxide and it is as follows.
Concentration or molarity of the sodium hydroxide = $\dfrac{\text{number of moles of KHP}}{\text{volume of NaOH in liters}}$
- Volume of sodium hydroxide in ml = 26.55 $\times {{10}^{-3}}$ .
- We can calculate the molarity of the sodium hydroxide with known values and it is as follows.
Concentration or molarity of the sodium hydroxide = \[\dfrac{3.398\times {{10}^{-3}}}{26.55\times {{10}^{-3}}}=0.1280mol/lit\]
- Therefore the molarity of 26.55 ml of sodium is 0.1280 mol/lit.

Note:
We have to know the molecular weight of the KHP to calculate the number of moles of KHP and we should first calculate the number of moles of KHP and later by using the number of moles of KHP we can calculate the molarity of the sodium hydroxide.