A sample of potassium hydrogen phthalate (KHC_8H_4O_4), which is an acid, with a

Question

A sample of potassium hydrogen phthalate (KHC_8H_4O_4), which is an acid, with a mass of 0.5827 g is dissolved in water and used to standardize a solution of calcium hydroxide. An endpoint is reached when 39.41 mL of calcium hydroxide has been added. Determine the molarity (in mol/L) of the calcium hydroxide solution. Report your answer to four significant figures. The standardized calcium hydroxide solution is then used to titrate 13.07 mL of a solution of trifluoroacetic acid (F_3CCOOH). An endpoint is reached when 16.89 mL of calcium hydroxide has been added. Determine the molarity (in mol/L) of the trifluoroacetic acid solution. Report your answer to four significant figures.

Explanation / Answer

Molarity= moles of solute/ liters of solution
moles of solute= sample size/ molar mass= (.5827 g) / (204.22g/mol)= 0 .00285 moles
liters of solution=0.03941 L

Molarity (converted to mmoles/mL)= 2.853 millimoles/ 39.41 mL= 0.072 M

2.

1 mole of CF3COOH neutralised by 1 mole of Ca[OH]2

moles of Ca[OH]2 = 16.89 mL x 0.072 == 1.216 milli moles

Molarity = 1.216 milli moles / 13 mL == 0.094 M

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