Question

Determine the molarity of NaOH to three decimal places if 19.20 mL of this NaOH were used to titrate 0.322 g of KHP (MM 204.22 g/mol)

Answer 1

The balanced equation of reaction they describe is the following:

NaOH + KHP → KNaP + H2O

By stoichiometry, we have that the ratio NaOH and KHP is one to one, which means that if we have n moles of KHP we will need the same n moles NaOH.

Now, let's determine the moles of KHP using its molecular mass:

`\begin{gathered} \text{Moles of KHP = g of KHP}*(1molKHP)/(204.22gKHP) \\ \text{Moles of KHP = 0.322g of KHP}*(1molKHP)/(204.22gKHP) \\ \text{Moles of KHP = }1.577*10^(-3)molKHP \end{gathered}`

Therefore, we must add 1.577x10^-3 moles of NaOH. The molarity is defined as:

`\begin{gathered} \text{Molarity = }\frac{\text{Moles of solute}}{L\text{ of solution}} \\ \text{Molarity}=\text{ }\frac{\text{1.577}*10^(-3)mol}{19.20mL*(1L)/(1000mL)} \\ \text{Molarity}=0.082M \end{gathered}`

The molarity of NaOH solution is 0.082M