Question

The solubility of sodium chloride in water at 290K is 35.8 kg/100 kg water. What is the mass fraction of sodium chloride in the solution?

• A. 0.264
• B. 0.358
• C. 0.642
• D. 0.736

Hint:

To calculate mass fraction, divide the mass of the solute by the total mass of the solution (solute + solvent).

Answer 1

The Correct Option is A

Step 1: Use the formula for mass fraction. 
The mass fraction of sodium chloride in the solution is given by: \[ \text{Mass fraction} = \frac{\text{Mass of solute}}{\text{Mass of solute} + \text{Mass of solvent}} \] Here, the mass of solute is the amount of sodium chloride, and the mass of solvent is the amount of water. 
Step 2: Substitute the given values. 
Given:
Solubility of sodium chloride = 35.8 kg/100 kg of water,
Mass of solvent (water) = 100 kg,
Mass of solute (sodium chloride) = 35.8 kg.
Thus, the mass fraction is: \[ \text{Mass fraction} = \frac{35.8}{35.8 + 100} = \frac{35.8}{135.8} \approx 0.264. \] 
Final Answer: The mass fraction of sodium chloride is 0.264.