What is the mass percent of ethylene glycol in the unknown solution? Aqueous eth

Question

What is the mass percent of ethylene glycol in the unknown solution?

Aqueous ethylene glycol (HOCH_2CH_2OH, FW = 62.07 g/mol) solution with a mass of 281.7 mg is titrated with 44.1 mL of 0.0657 M Ce^4+ in 4 M HCIO_4. The solution is held at 60 degree C for 15 minutes to oxidize the ethylene glycol to formic acid (HCO_2H) and carbon dioxide. The excess Ce^4+ is titrated with 11.19 mL of 0.0395 M Fe^2+ to a ferroin end point. What is the mass percent of ethylene glycol in the unknown solution? Number %

Explanation / Answer

1 mole of ethylene glycol reacts with 1 mole of Ce4

Total moles of Ce4 = 0.0657 M x 44.1 ml = 2.898 mmol

Actual moles of Ce4 reacted with ethylene glycol = 2.898 mmol - 0.0395 M x 11.19 ml = 2.456 mmol

mass of ethylene glycol = 2.456 mmol x 62.07 g/mol = 152 mg

mass percent of ethylene glycol in the unknown solution = 152 x 100/281.7 = 53.96%

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