An aqueous solution of sodium hydroxide (NaOH) was standardized by titrating it

Question

An aqueous solution of sodium hydroxide (NaOH) was standardized by titrating it against 25.00 mL of a solution prepared by dissolving 2.138g of potassium hydrogen phthalate (KHP) in 100.00 mL of DI water. The initial reading taken from the buret containing the NaOH was 0.48m L and the final volume reading was 27.64mL. What is the molarity of the NaOH solution? An aqueous solution of sodium hydroxide (NaOH) was standardized by titrating it against 25.00 mL of a solution prepared by dissolving 2.138g of potassium hydrogen phthalate (KHP) in 100.00 mL of DI water. The initial reading taken from the buret containing the NaOH was 0.48m L and the final volume reading was 27.64mL. What is the molarity of the NaOH solution?

Explanation / Answer

HP- + OH- => P^2- + H2O

KHP reacts in 1:1 mole ratio with NaOH

Molar mass of KHP is 204.22g/mol

Assume that volume doesn't change when solution is being made, since we have no idea of obtaining this information

2.138g x (1mol/204.22g) = 0.01047 mol

This is in 100 mL, so molarity is

0.01047mol/0.1L => 0.1047 mol/L

Thus, in 25mL of this solution has

0.025L x 0.1047 mol/L = 0.002617 mol

which is also the number of mol of NaOH

Difference in volume is 27.16 mL

0.002617 mol / 0.02716 L = 0.09637 mol/L

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