Question

1.A sample of potassium hydrogen phthalate (KHC8H4O4), which is an acid, with a mass of 0.4749 g is dissolved in water and used to standardize a solution of strontium hydroxide. An endpoint is reached when 38.96 mL of strontium hydroxide has been added. Determine the molarity (in mol/L) of the strontium hydroxide solution. Report your answer to four significant figures.​

2.The standardized strontium hydroxide solution is then used to titrate 27.22 mL of a solution of formic acid (HCOOH). An endpoint is reached when 15.97 mL of strontium hydroxide has been added. Determine the molarity (in mol/L) of the formic acid solution. Report your answer to four significant figures.

Answer 1

1) 2KHC8H4O4 + Sr(OH)2 -------> Sr(KC8H4O4)2 + 2H2O

soichiometrically, 1mole of Sr(OH)2 react with 2mole of KHC8H4O4

mass of KHP = 0.4749g

molar mass of KHP = 204.22g/mol

No of mole of KHP = 0.4749g/204.22(g/mol) = 0.002325mol

0.002325 mole of KHP react with 0.0011625mole of Sr(OH)2

Volume of Sr(OH)2 solution = 38.96ml

Molarity of Sr(OH)2 = (0.0011625mol/38.96ml)×1000ml = 0.02984M

2) Sr(OH)2 + 2HCOOH ---------> Sr(HCOO-)2 + 2H2O

stoichiometrically, 1mole of Sr(OH2 react with 2mole of HCOOH

No of mole of Sr(OH)2 consumed = (0.02984mol/1000ml)×15.97ml = 0.0004765mol

0.0004765mol of Sr(OH)2 react with 0.000953mol of HCOOH

Volume of HCOOH solution = 27.22ml

Molarity of HCOOH = (0.000953mol/27.22ml)×1000ml = 0.0350M