In: Chemistry
A 19.04 g mixture of sugar (C12H22O11) and table salt (NaCl) is dissolved in 233 g of water. The freezing point of the solution was measured as -3.58 °C. Calculate the mass percent of sugar in the mixture. A list of Kf values can be found here.
Let x g of sugar are present in the the mixture. Mass of mixture is 19.04 g. Mass of NaCl in the mixture .
The molar masses of sugar and NaCl are 342.3 g/mol and 58.4 g/mol.
Number of moles of sugar
Number of moles of NaCl
Since 1 mole of dissociates to give two moles of ions in solution, we multiply number of moles of NaCl with 2 to obtain number of moles of ions from NaCl
Total number of moles of particles from sugar and NaCl
Mass of water is 233 g or
Molality of solution
.....(1)
The depression in the freezing point
Molality ......(2)
But (1)=(2)
Mass percent of sugar in the mixture