The concentration of a solution refers to the amount of solute dissolved in a given amount of solvent. It can be expressed as a percentage by mass by taking the ratio of the mass of the solute to the total mass of the solution and multiplying by 100. Examples are provided to demonstrate calculating concentration as a percentage by mass using various masses of solutes and solvents in solutions.

1. the concentration
 of a solution is the quantity of
a solute that is contained in a
particular quantity of solvent or
solution.

12. Qualitative description- observation to
gather non-numerical data
- use descriptive words

18. Example:
A solution is prepared by mixing 30g
of NaCl and 180g H2O. What is the
concentration of NaCl in % by mass?

19.  Given: 30g NaCl- mass of solute
 80g H20- mass of solvent
 Mass of solution- 30g NaCl + 80g H20= 210 g
 Percent by mass= ( mass of solute / mass of solution ) x 100
 (30g / 210g) x 100
 = 0.1428 x 100

= 14 %

20. This is a paired activity.Find your
partner to answer the given problem.
Solve the following problem by using
Percent by mass.
1.What is the percent by mass
concentration of a sugar that contains
8 g of sugar dissolved in 15 g of water?

21. A 120 g aqueous acid solution is
labeled to contain 15% HCl by mass.
How many grams of pure HCl are
contained in the solution?

22. What is the importance of concentration of
solutions in our life?

23. A solution of gases contains 25 g oxygen and
50 g helium. What is the percentage
composition by mass?

24. An alloy is prepared by mixing 60g
copper and 30 g zinc. Find the
percentage by mass of copper and zinc