Question

119. In analytical chemistry, bases used for titrations must often be standardized; that is, their concentration must be precisely determined. Standardization of sodium hydroxide solutions can be accomplished by titrating potassium hydrogen phthalate (KHC8H4O4), also known as KHP, with the NaOH solution to be standardized. a. Write an equation for the reaction between NaOH and KHP. b. The titration of 0.5527 g of KHP required 25.87 mL of an NaOH solution to reach the equivalence point. What is the concentration of the NaOH solution

Answer 1

NaOH + KHC8H4O4 → NaKC8H4O4 + H2O

Concentration NaOH = 0.105 M

Step-by-step explanation:

Step 1: Data given

Mass of KHP = 0.5527 grams

Molar mass KHP = 204.22 g/mol

Volume of NaOH = 25.87 mL

Step 2: The balanced equation

NaOH + KHC8H4O4 → NaKC8H4O4 + H2O

Step 3: Calculate moles KHP

Moles KHP = mass KHP / molar mass KHP

Moles KHP = 0.5527 grams / 204.22 g/mol

Moles KHP = 0.002706 moles

Step 4: Calculate moles NaOH

For 1 mol NaOH we need 1 mol KHP to react

For 0.002706 moles KHP we need 0.002706 moles NaOH

Step 5: Calculate concentration NaOH

Concentration = moles / volume

Concentration NaOH = 0.002706 moles / 0.02587 L

Concentration NaOH = 0.105 M

Answer 2

0.1046M NaOH solution

Step-by-step explanation:

a. KHP is a salt used as primary standard because allows direct standarization of bases solutions. The reaction of KHP with NaOH is:

KHP + NaOH → H₂O + KP⁻ + Na⁺

As you can see, KHP has 1 acid proton that reacts with NaOH.

Molar mass of KHP is 204.22g/mol; 0.5527g of KHP contains:

0.5527g KHP × (1mol / 204.22g) = 2.706x10⁻³moles of KHP. As 1 mole of KHP reacts per mole of NaOH, at equivalence point you must add 2.706x10⁻³moles of NaOH

As you spent 25.87mL of the solution, molarity of the solution is:

2.706x10⁻³moles of NaOH / 0.02587L = 0.1046M NaOH solution