HW # 12 – Read Class Notes; Complete Handout Front Side Only!

Aim: How much solute can a solvent hold? Do Now: Based on Reference Table F, which of these salts is the best electrolyte?

(1) sodium nitrate (3) silver chloride (2) magnesium carbonate (4) barium sulfate

Based on Reference Table F, which of these salts is the best electrolyte?

(1) sodium nitrate (3) silver chloride (2) magnesium carbonate (4) barium sulfate Electrolyte: a substance that conducts electricity when dissolved in water.

Dissolved = Soluble Sodium nitrate (Soluble) Magnesium carbonate (Insoluble) Silver chloride (Soluble) (Insoluble) Barium sulfate (Soluble) (Insoluble)

Solubility: the amount of a substance that will dissolve in a given amount of another substance at a specified temperature Ex. 40 grams of NaCl can dissolve in 100 grams of water at 100°C Dilute: very little solute compared to solvent When the solute amount is less than half the amount of the solvent = 5g NaCl/100g water Concentrated: a lot of solute compared to solvent When the solute amount is more than half the amount of the solvent = 85g NaCl/100g water

Water has its limits!

Saturated solution: contains the most solute that the solvent will allow at a given temperature Unsaturated solution: contains less solute than a saturated solution Supersaturated solution: contains more solute than a saturated solution

Supersaturated solution:

The rate of dissolving < the rate of crystallization.

Unsaturated solution:

The rate of dissolving > the rate of crystallization.

Saturated solution: The rate of dissolving = the rate of crystallization.

SOLUTION EQUILIBRIUM

How to Use Table G

X axis = temperature (°C) Y axis = amount of solute per 100 g of H 2 0 Saturated solution: “on the line” Ex. How many grams of NaCl will saturate 100g of H 2 0 at 100°C?

Answer: 40 grams Unsaturated: “below the line” Anything less than 40 grams.

Supersaturated: “above the line” Anything more than 40 grams.

How many grams of NaNO 3 are needed to saturate 200g of H 2 0 at 40°C?

(watch for multiples of 100g!!!)

Answer: At 100g of H 2 0 = 105g.

At 200g of H 2 0, 105g x 2 = 210g At 50g of H 2 0, 105g / 2 = 52.5g

A solution contains 35 grams of KNO3 dissolved in 100 grams of water at 40°C.

How would you describe this solution?

- Unsaturated - Dilute How much more KNO3 would have to be added to make it a saturated solution?

(1) 29 g (2) 24 g (3) 12 g (4) 4 g

A saturated solution of NaNO3 is prepared at 60.°C using 100. grams of water. As this solution is cooled to 10.°C, NaNO3 precipitates (settles) out of the solution.

The resulting solution is saturated. Approximately how many grams of NaNO3 settled out of the original solution?

(1) 46 g (2) 61 g (3) 85 g (4) 126 g