Question 1

What is mass percent?

Accepted Answer

Mass percent (weight percent, w/w%) is the mass of solute divided by the total mass of solution, multiplied by 100. For example, a 5% NaCl solution contains 5 g of NaCl per 100 g of solution.

Question 2

How is mass percent different from molarity?

Accepted Answer

Mass percent uses mass ratios and is temperature-independent. Molarity uses moles per liter of solution and changes with temperature (since volume changes). Mass percent does not require knowing the molar mass.

Question 3

Is mass of solution the same as mass of solvent?

Accepted Answer

No. Mass of solution = mass of solute + mass of solvent. For example, dissolving 10 g NaCl in 90 g water gives a 100 g solution with 10% mass percent.

Question 4

What are common mass percent values?

Accepted Answer

Common examples: household bleach is ~5% NaOCl, vinegar is ~5% acetic acid, saline solution is 0.9% NaCl, rubbing alcohol is 70% isopropanol.

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