Question

Potassium hydrogen phthalate is a solid, monoprotic acid frequently used in the laboratory as a primary standard. It has the unwieldy formula of KHC8H4O4. This is often written in shorthand notation as KHP. If 32.5 mL of a potassium hydroxide solution are needed to neutralize 3.74 grams of KHP, what is the molarity of the potassium hydroxide solution? __M

Answer 1

we have the Balanced chemical equation as:

KHC8H5O4 + KOH ---> K2HC8H4O4 + H2O

Molar mass of KHC8H5O4 = 1*MM(K) + 5*MM(H) + 8*MM(C) + 4*MM(O)

= 1*39.1 + 5*1.008 + 8*12.01 + 4*16.0

= 204.22 g/mol

mass of KHC8H5O4 = 3.74 g

we have below equation to be used:

number of mol of KHC8H5O4,

n = mass of KHC8H5O4/molar mass of KHC8H5O4

=(3.74 g)/(204.22 g/mol)

= 1.831*10^-2 mol

From balanced chemical reaction, we see that

when 1 mol of KHC8H5O4 reacts, 1 mol of KOH reacts

mol of KOH reacted = (1/1)* moles of KHC8H5O4

= (1/1)*1.831*10^-2

= 1.831*10^-2 mol

This is number of moles of KOH

volume , V = 32.5 mL

= 3.25*10^-2 L

we have below equation to be used:

Molarity,

M = number of mol / volume in L

= 1.831*10^-2/3.25*10^-2

= 0.5635 M

Answer: 0.563 M