Mass percentage (w/w)
Defines concentration as mass of solute per 100 units mass of solution.
What is Mass percentage (w/w)?
The mass of the solute in grams present in 100 grams of the solution.
Key formula / rule: Mass Percentage (w/w)
Key points
- Define mass percentage (w/w).
- Calculate mass percentage given the mass of solute and solvent.
- Understand the relationship between mass percentage, solute mass, and solution mass.
- Identify situations where mass percentage is the preferred concentration unit.
Common exam trap
Confusing mass of solvent with mass of solution.
Definitions
- Term
Mass Percentage (w/w)
- Meaning
The mass of the solute in grams present in 100 grams of the solution.
- Term
Solution
- Meaning
A homogeneous mixture of two or more substances.
- Term
Solute
- Meaning
The substance that is dissolved in a solvent to form a solution.
- Term
Solvent
- Meaning
The substance that dissolves the solute to form a solution.
Learning objectives
Define mass percentage (w/w).
Calculate mass percentage given the mass of solute and solvent.
Understand the relationship between mass percentage, solute mass, and solution mass.
Identify situations where mass percentage is the preferred concentration unit.
Formulae
- Name
Mass Percentage (w/w)
- Note
Where Mass of solution = Mass of solute + Mass of solvent.
- Expression
Mass % = (Mass of solute / Mass of solution) × 100
Prerequisites
Basic understanding of mass and units.
Concept of solute and solvent.
Concept of solution.
Common mistakes
Confusing mass of solvent with mass of solution.
Incorrectly calculating the denominator (using only solvent mass).
Forgetting to multiply by 100 to express as a percentage.
Keywords
Mass percentage
Concentration
Solution
Solute
Solvent
Percent by mass
w/w
Practice preview
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What is the mass percentage of glucose (molar mass = 180 g/mol) in an aqueous solution containing 18 g of glucose in 182 g of water?…
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A solution is prepared by dissolving 5 g of salt in 45 g of water. What is the mass percentage of the salt in the solution?…
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