Question

a quantity of 18.68 mL of KOH solution is needed to neutralize 0.4218 g of KHP. What is the concentration (in molarity) of the KOH solution?

Answer 1

To neutralize an acidic substance with the basic solution, the number of moles should be equal. First, we calculate for the number of moles of KHP.

molar mass of KHP = (1 mol K)(39.1 g K/1 mol K) + (1 mol H)(1 g H/1 mol H) + (1 mol P)(30.97 g P / 1 mol P) = 71.07 g KHP/ mol

number of moles KHP = (0.4218 g KHP) x (1 mol KHP / 71.07 g KHP)
        n = 0.0059 moles

Let M be the molarity of the solution and equating the number of moles,
     0.0059 moles = (18.68 mL)(1 L/1000 mL)(M)
            M = 0.32 moles/L

ANSWER: 0.32 M