Grams in every 100 grams
Mass by mass percentage (% m/m).
Salt in 100 g
You dissolve 10 g of salt in 90 g of water.
About how much of the whole solution is salt?
What this lesson covers
The idea
Mass by mass percentage (% m/m, numerically equal to % w/w) = (mass of solute ÷ mass of solution) × 100, the grams of solute per 100 g of solution, where solution mass = solute mass + solvent mass.
Salt in 100 g
You dissolve 10 g of salt in 90 g of water.
About how much of the whole solution is salt?
- One tenth of it
- Nine tenths of it
- Half of it
Fill the 100 cells
Change the grams of salt and water. Watch the cells. Make 10 % twice.
% m/m
Mass by mass percentage (% m/m or % w/w) = (mass of solute ÷ mass of solution) × 100. It tells how many grams of solute are in 100 grams of the solution. Mass of solution = mass of solute + mass of solvent.
Example 5.1. 10 g of salt is dissolved in 90 g of water. Mass of solution = 10 g + 90 g = 100 g. Percentage = (10 ÷ 100) × 100 = 10 % m/m.
It is also used for spice mixtures, milk powder, and to label salt, sugar or protein in packaged food. % m/m and % w/w are numerically equal.
Notes
% m/m = (mass of solute ÷ mass of solution) × 100: the grams of solute in 100 g of solution.
Check yourself
20 g of salt is dissolved in 80 g of water. What is the mass of the solution?
Answer: 100 g
20 g + 80 g = 100 g.
20 g of salt is dissolved in 80 g of water. What is the mass by mass percentage?
Answer: 20 % m/m
(20 g ÷ 100 g) × 100 = 20 % m/m.
In the % m/m formula, the divisor is the mass of…
5 g of salt is dissolved in 45 g of water. Find the % m/m.
Answer: 10 % m/m
(5 ÷ 50) × 100 = 10 % m/m.
- the solvent only. Use the whole solution.
- the solute only. The solute is the top of the fraction.
- the whole solution — correct. Yes. Solute plus solvent.