Concentration & Solutions – Part 2

How do we talk about them?

Parts per million (ppm)

• (%) Per cent: out of a hundred• Per million: out of a million

• 8 parts (pieces of pie)• 1 part contaminated

= 1 part per 8

• 1 million parts(pieces of pie)

• 1 part contaminated= 1 ppm

• 1 part contaminated + 999,999 normal parts

What does 1 ppm look like?

• 1 drop of water in 50 L• ~30 seconds in a year• 1 penny in $10 000

Real-life examples

• 1 ppm of chlorine in a pool to kill bacteria• 4 ppm of oxygen needed for fish in ocean

water• 0.01 ppm of arsenic allowed in tap water• 0.05 ppm insecticide (chlorpyrifos) allowed in

bananas

What are the “parts”?

ppm in mass

1 ppm1 g

1 000 000 g=1 mg solute1 kg solution

1 mg1 000 g= =

• 1 ppm of chlorine in a pool– 1 mg in 1 kg of pool water

• 60 ppm of contaminant in soil– 60 mg in 1 kg of soil

• We can smell H2S at 0.1 ppm concentration in air– 0.1 mg in 1 kg of air

1. Solution A has a concentration of 0.65 mg/kg and Solution B has a concentration of 0.225 g/kg. What are their concentrations in ppm?

2. An 800 g sample of soil from a yard contains 5.3 g of pollutant. What is the concentration of pollutant in ppm?

3. Another 650 g sample of soil has a pollutant concentration of 7 ppm. How much pollutant is in the soil sample?

4. Whole wheat bread has 850 ppm of magnesium. How much magnesium is in 1 slice of bread, if one slice has a mass of 30 g?

ppm for aqueous solutions

• # parts of solute in 1 million parts of solution

** Solution often substituted for water

1 ppm 1 g1 000 000 mL=

1 mg1 L

1 g1 000 L= =

1 mg solute1 L solution (water)=

ppm for aqueous solutions

• # parts of solute in 1 million parts of solution

1 ppm =1 mg solute

1 L solution (water)

• 4 ppm of oxygen needed for fish in ocean water– 4 g oxygen in 1 L of ocean water

• 0.01 ppm of arsenic allowed in tap water– 0.01 g of arsenic in 1 L of tap

water

1. The Gatorade “Thirst Quencher” has approximately 51 mg/L of potassium. What is the concentration of potassium in ppm?

2. A solution has a concentration of 1.25 g/L. What is its concentration in ppm?

3. A solution has a concentration of 0.5 mg/mL. What is its concentration in ppm?

4. Water in a lake is contaminated. A 50 mL sample has 4.8 mg of contaminant. What is the concentration in ppm?

1. Write out what values the question gives you

2. Write out the ppm equation3. Ensure the values are in the correct

units and convert if necessary4. Put the values into the equation5. Solve the equation6. Answer the question in a sentence

mgL

mgkg

ppm =

ppm =

Steps to follow to answer ppm questions