Percent Composition by Mass

A 4 g sugar cube (Sucrose: C₁₂H₂₂O₁₁) is dissolved in a 350 ml teacup of 80 °C water. What is the percent composition by mass of the sugar solution?
Given: Density of water at 80 °C = 0.975 g/ml

Definition

Percent Composition by Mass is the mass of the solute divided by the mass of the solution (mass of the solute plus mass of the solvent), multiplied by 100.

Step 1 - Determine mass of solute Solute is 4 g of C₁₂H₂₂O₁₁

Step 2 - Determine mass of solvent

density = mass/volume
mass = density x volume
mass = 0.975 g/ml x 350 ml
mass = 341.25 g

Step 3 - Determine the total mass of the solution

m_solution = m_solute + m_solvent
m_solution = 4 g + 341.25 g
m_solution = 345.25 g

Step 4 - Determine percent composition by mass of the sugar solution.

percent composition = (m_solute / m_solution) x 100
percent composition = ( 4 g / 345.25 g) x 100
percent composition = ( 0.0116 ) x 100
percent compostion = 1.16%

Answer:

The percent composition by mass of the sugar solution is 1.16%