solution concentrations. percent by mass (m/m) mass of solute mass of solution ×100solution =...
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Solution Concentrations
Percent by Mass (m/m)
Mass of soluteMass of solution
×100 Solution = solute + solvent
Example 1
An aquarium must contain 13.6 g NaCl per 100.0 g of water. What is the percent by mass (m/m) of NaCl in the solution?
Solute:13.6g (smaller #)
Solvent: 100.0g (larger #)
Solution: 113.6g
+13.6
113.6×100 = 11.97% ≈ 12.0%
solut
esolve
nt
Mass of soluteMass of solution
×100
Water is
always a
solvent!
!!
Example 2
You have a 650.0g KCL solution. If the percent by mass is 1.25% (m/m), how many grams of solute is in the solution? How many grams of solvent are in the solution?
Solution: 650.0g
Solute: 8.13g
Solvent = 641.87g ≈ 642g
−
solute650.0
×100 = 1.25%
Solute = 8.13g
First find solute:
Then remember: solute + solvent = solutionand solve for solvent
Percent by Volume (v/v)
Volume of solute
Volume of solution
×100 Solution = solute + solvent
Example 3
What is the percent by volume of ethanol in a solution that contains 45mL of ethanol dissolved in 145mL of water?
Solute: 45mL (smaller #)
Solvent: 145mL (larger #)
Solution: 190mL
+45
190×100 = 23.68% ≈ 24%
solven
tsolute
Then remember: solute + solvent = solutionand solve for solvent
Example 4
If you have 200.0 mL of a 35.0% aqueous solution of ethanol, what volume of ethanol and water are in the solution?
Solution: 200.0mL
Solute: 70.0mL
Solvent = 130.0mL
≈ 130. or 1.3×102 mL
−
solute200.0
×100 = 35.0%
Solute = 70.0mL
Means dissolved in water; water is the solvent
First find solute:
Parts Per Million (ppm)
SoluteSolution
×1061 ppm = 1mg/L
Example 5
If 25 grams of a chemical is dissolved in 75 grams of water, what is the concentration of the chemical in parts per million (ppm)?
Solute: 25g (smaller #)
Solvent: 75g (larger #)
Solution: 100g
+
25100
×106 = 250,000 or 2.5×105 g
Example 6
Suppose 17 grams of sucrose is dissolved in 183 grams of water. What is the concentration of sucrose in ppm?
Solute: 17g (smaller #)
Solvent: 183g (larger #)
Solution: 200g
+
17200
×106 = 85,000 or 8.5×104 g
Example 7
150 mL of an aqueous sodium chloride solution contains 0.0045g NaCl. Calculate the concentration of NaCl in parts per million (ppm). Remember 1ppm = 1 mg/L
0.0045g 1000mg 1000mL 150mL 1g 1L
= 30 mg/L = 30 ppm
So change the mL into L and the g
into mg
Example 8
Convert 0.0035% NaCl by mass into parts per million of NaCl.
* Think of 0.0035% like your grade on a test; 0.0035% means 0.0035 out of 100
0.0035100
×106 = 35ppm