Question

The sugar fructose contains 40.0% C, 6.7% H, and 53.3% O by mass. A solution of 11.7 g of fructose in 325 g of ethanol has a boiling point of 78.59 °C. The boiling point of ethanol is 78.35 °C, and Kb for ethanol is 1.20 °C/m. Assuming ideal solution behavior, what is the molecular formula of fructose?

Answer 1

The molecular formula of fructose is C₆H₁₂O₆.

What is the molecular formula of fructose?

The molecular formula is derived in the following steps:

Step 1. the molality of the solution is determined first

Molality = Change in boiling point/Kb

Molality = (78.59 - 78.35)/1.2 = 0.2 molal

Step 2. Moles of solute is determined.

Moles of solute = molality * mass of solvent (kg)

moles = 0.2 * 0.325 = 0.065

Step 3. Molar mass of fructose = mass/moles

Molar mass of fructose = 11.7/0.065 = 180 g/mol

Step 4: Mole ratio of constituent elements

Carbon = 40% * 180/12 = 6

Hydrogen = 6.7% * 180/1 = 12

Oxygen = 53.3% * 180/16 = 6

Therefore, the molecular formula of fructose is C₆H₁₂O₆.

In conclusion, the molecular formula of fructose is derived from the molality of the solution.

Learn more molality at: brainly.com/question/9149034

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