Maleic acid is a carbon-hydrogen-oxygen compound used in dyeing and finishing fa

Question

Maleic acid is a carbon-hydrogen-oxygen compound used in dyeing and finishing fabrics and as a preservative of oils and fats. In a combustion analysis, a 1.054-g sample of maleic acid yields 1.599 g of CO2 and 0.327 g of H2O. When 0.609 g of maleic acid is dissolved in 25.00 g of glacial acetic acid, the freezing point drops by 0.82 C. Maleic acid does not ionize in glacial acetic acid, which has a freezing-point depression constant of Kf=3.90 C/m. In a titration experiment, a 0.4250-g sample of maleic acid is dissolved in water and requires 34.03 mL of 0.2152 M KOH for its complete neutralization. The pH of 0.215 g of maleic acid in 50.00 mL of aqueous solution is found to be 1.80.

Given that the ionizable H atoms are associated with carboxyl groups, draw a plausible structure for maleic acid.

Explanation / Answer

In a combustion analysis, a 1.054-g sample of maleic acid yields 1.599 g of CO2 and 0.327 g of H2O.

find mass using molar masses
1.599g of CO2 @ (12.01 g Carbon) / (44.01 g CO2) = 0.436 grams of Carbon
0.327g of H2O @ (2.016 g Hydrogen) / (18.01 g/mol H2O) = 0.037 grams of Hydrogen
1.054-g sample - 0.436 grams of Carbon - 0.037 grams of Hydrogen = 0.581 grams of oxygen


now use molar masses to find moles
0.436 grams of Carbon @ 12.01 g/mol = 0.0363 mol C
0.037 grams of Hydrogen @ 1.008 g/mol = 0.0367 mol H
0.581 grams of oxygen @ 16.00 g/mol = 0.0363 mol O

empirical formula is CHO

Atomic weights:

C=12,

H=1

, O=16,

C4H4O4=116.

=

=34.03mL KOH /0.4250g maleic acid x 116gMA/1mol maleic acid x 0.2152molKOH/1000mL KOH = 1.999,

which is about 2

So there are two ionizable H atoms in maleic acid

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