Concentration Part D

2. Solution Concentration
Concentration = quantity of solute
quantity of solution (not solvent)
There are 3 basic ways to express concentration:
1) percentages,
2) ppm and ppb (used for very low concentrations)
3) molar concentrations

3. 1. Percent concentration
% concentration can be in
1a) % V/V
1b) % W/W
1c) % W/V

4. %V/V = volume of solute (mL or L) X 100%
Volume of solution (mL or L)
1. 140 mL of acetic acid is present in a 500 mL bottle of
solution? What is the percentage by volume
concentration of acetic acid? 28% V/V
2. Gasohol fuel is a solution of ethanol and gasoline. A
typical gasohol mixture available across Canada
contains 4.1 L of ethanol in a 55-L tank of fuel. What is
the percentage by volume concentration of ethanol? 7.5
3. What is approximate % V/V if 30 mL of pure ethanol is
added to 250 mL of water? 11% V/V
1a) Percent volume by volume
concentration

5. • %m/m = mass of solute (g or kg) X100%
mass of solution (g or kg)
1. What is the % W/W if 8.0 g copper is added to enough
zinc to produce 100 g of an alloy? 8% W/W.
2. Brass is a copper-zinc alloy. If the concentration of zinc
is relatively low, the brass has a golden color and is
often used for inexpensive jewellery. If a 35.0 g
pendant contains 1.7 g of zinc, what is the percentage
weight by weight of zinc in brass? 4.9% W/W
3. What is the % m/mof copper in an alloy when 10 kg of
Cu is mixed with 250 kg of Zn? 3.8 % W/W
1b) Percent mass by mass concentration

6. • % W/V = mass of solute (g) X 100%
volume of solution (mL)
• Can use g/ml or kg/L
1. Solder flux, available at hardware stores, contains 16 g of zinc
chloride in 50 mL of solution. The solvent is HCl (aq). What is
the percentage weight by volume of zinc chloride in the
solution? 16 g / 50 mL = 32% W/V
2. If 250 g of sodium chloride is present in 3 L of solution, what is
the percentage weight by volume of sodium chloride?
250g/3000ml = 8.5% W/V
1c) Percent mass by volume
concentration

7. 2. Very low concentrations
• Expressed in parts per million (ppm)
or parts per billion (ppb)
• A type of m/m or m/V concentration
• E.g. chlorine concentration in a swimming
pool may be expressed as ppm
• 1 mg/L 1 ppm 1 mg/1000L 1 ppb
1 mg/kg 1 mg/1000kg
• 1 g/L 1 ppt
1 g/kg

8. Calculation: ppt
• 45 g/kg of a solid
• We know that 1 ppt = 1 g/1000 g
• Set up proportion
• ‘x’ g = 45 g
1000 g 1000g
• x = 45 ppt

9. Calculation: ppm
• 4.5 g/250L of a water solution
• We know that 1 ppm = 1 mg/1L
• Set up proportion
• ‘x’ mg = 45000 g
1 L 250 L
• x = 180 ppm

10. Calculation: from ppm
• 5 ppb Lead in water as V/V%
• We know 1 ppb = 1 mg/1 kg
• Set up proportion
• ‘x’ mg = 5 mg = 5 mg x 100%
• 1 kg 1000 g 1000,000 mg
• 0.0005% V/V