1. 1. 20g of NaN03 is dissolved in 65g of water at 80⁰C
1. 20g of NaN03 is dissolved in 65g of water at 80⁰C. Explain why this solution is unsaturated.
20g NaN03 / 65g H2O = X g NaN03 / 100g H2O
(20g NaN03 / 65g H2O)*100g H2O = 31g NaN03
From the solubility curve, a saturated solution at 80⁰C would contain approximately 152g NaN03 / 100g H2O.
This solution contains only 31 g NaN03 / 100 g H2O and is therefore unsaturated.

2. 2. What additional amount of NaNO3 would be required to saturate this solution?
152g NaN03 / 100g H2O = X g NaN03 / 65g H2O
(152g NaN03 / 100g H2O)*65g H2O = 99g NaN03
The solution would require 99g of NaN03 to saturate it. 99g – 20g = 79g NaN03.
The solution would require an additional 79g NaN03 to be saturated.

3. Concentration

4. Concentration
Concentration is a measure of the amount of solute that is dissolved in a given quantity of solvent.

5. Representations of Concentration
There are many ways to express concentration including:
g/L = grams of solute in 1 L of solution
ppm = parts per million
ppb = parts per billion
Example: 10 ppb iron in water = 10 particles of iron in 1 billion particles of water

6. United States Environmental Protection Agency: EPA Standards
Arsenic
Non-cancer effects can include thickening and discoloration of the skin, stomach pain, nausea, vomiting; diarrhea; numbness in hands and feet; partial paralysis; and blindness. Arsenic has been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver, and prostate.
EPA has set the arsenic standard for drinking water at .010 parts per million (10 parts per billion).

7. United States Environmental Protection Agency: EPA Standards
Lead and copper
Lead and copper enter drinking water through plumbing materials. Exposure to lead and copper may cause health problems ranging from stomach distress to brain damage.
If lead concentrations exceed 15 ppb or copper concentrations exceed 1.3 ppm in more than 10% of taps sampled, the system must undertake a number of actions to control corrosion. If the action level for lead is exceeded, the system must also inform the public about steps they should take to protect their health.

8. Concentration
In SI concentration is defined as the number of moles of a solute dissolved in 1L of solution and termed Molarity.
Molarity (M) is measured in moles/L.
Note: the volume is the measurement of the volume of the total solution not only the solvent.

9. Concentrations Molarity (M) = moles of solute litres of solute
Concentration = moles of solute
M = mol L

10. Concentrations
What is the concentration of a 5 L solution that contains 2 mol of glucose?
What is the concentration of a saline solution that contains 0.9g of NaCl per 100mL of solution?
How much solute is in 1.5 L of a 0.2 mol/L Na2SO4 solution?