Question

For the standardization of their sodium hydroxide solution a pair of students weighed out 0.4607 g of KHP (MM 204.22 g/mol). They found that it took 20.26 mL of their NaOH solution to reach the endpoint. What is the concentration of their NaOH solution in M?

Answer 1

Number of moles of KHP , n = Mass/ molar mass

                                         = 0.4607 g / 204.22(g/mol)

                                        = 2.26x10^-3 mol

The balanced molecular equation between KHP & NaOH is :

NaOH + KHP ------> NaKP+ H2O

From the balanced equation

1 mole of KHP reacts with 1 mole of NaOH

2.26x10^-3 mol of KHP reacts with 2.26x10^-3 mol of NaOH

Given Volume of NaOH is 20.26 mL = 20.26x10^-3 L

So Molarity of NaOH , M = Number of moles / volume of NaOH in L

                                    = 2.26x10^-3 mol / 20.26x10^-3 L

                                    = 0.111 M

Therefore the molarity of NaOH solution is 0.111 M