# Solubility Curves (continued)

The graph also shows that solubility increases with increasing temperature.

In general, this is because when the solute dissolves with heat absorption (endothermic dissolution), substances that dissolve with heat release (exothermic dissolution) tend to be less hot soluble.

Solubility curve of some salts
SOURCE: furg.br/furg/depto/quimica/solubi.html

SOURCE: luizclaudionovaes.sites.uol.com.br/solub.1.gif

Looking at the graph above about the solubility of some salts, answer:

1) What is the most soluble solute at 0 ° C?

It's KI, because it solubilizes almost 130g in 100g of water.

2) What is the approximate C.S. of NaNO3 at 20 ° C?
90

3) If the temperature of a solution drops from 70 ° C to 50 ° C, what is approximately the mass of KBr that will precipitate?

70 ° C = 90g
50 ° C = 80g
So: 90-80 = 10g

4) Which salt has solubility impaired by heating?

At2ONLY4

5) If the KNO3 solubilizes 90g in 100g of water at 50 ° C, how much will it solubilize when there is 50g of water?

x = 45g of KNO salt3

6) What kind of solution would form 80g of NH salt4Cl at 20 ° C?

Supersaturated solution.

 Acetic Acid 4% Acetic Acid Seasoning food Hydrated alcohol Hydrated 96% Household alcohol employed in cleaning Caustic soda NaOH (liquid) Grease Crust Removal and Soap Making Saline NaCl (aqueous) 0.9% Contact lens cleaning and medicine Formalin Methannel 40% Conservation of animal tissue Gold ring 18 carat gold Jewelry Sanitary water 5% sodium hypochlorite Bactericidal and bleach

### Regarding the solute / solvent ratio

The solution may be:

- Concentrated: large amount of solute relative to solvent.

Example: H2ONLY4 conc = 98% sulfuric acid + water

- Diluted: small amount of solute relative to solvent.

Diluting means adding more pure solvent to a given solution.

Example: water + pinch of table salt.