Mixtures, Solutions and Solubility Curves

Solutions & Solubility

How to

What is a Solution?

Solution: a mixture that has the same composition, color, density & taste throughout

A solution has two parts:

> Solute = substance dissolved (less)

> Solvent = does the dissolving (more)

Concentration

Concentration: percent by volume of solute in solvent

Concentrated: large amount of solute in solvent

Dilute: small amount of solute in solvent

Types of Solutions

• Unsaturated - able to dissolve more solute at a given temperature (not full)

• Saturated - contains all solute it can hold at a given temperature (full)

• Supersaturated - contains more dissolved solute than necessary to make a saturated solution (unstable)

What is Solubility?

Solubility: the maximum amount of solute that will dissolve in a certain amount of solvent at a given temperature

> Solute = substance dissolved

> Solvent = does the dissolving

Example: ___grams of salt (NaCl) dissolved in 100g of water at ___℃

Temperature and Solubility

Temperature affects how much of the solute can be dissolved by the solvent.

Solubility Curves: Are used to show how the solubility of a substance changes with temperature

Solubility Curve - Saturated

• Any point on a line represents a saturated solution

• In a saturated solution, the solvent contains the maximum amount of solute

• Example: At 90℃, 40g of NaCl in 100g H2O represent a saturated solution.

Solubility Curve - Unsaturated

• Any point below a line represents an unsaturated solution.

• In an unsaturated solution, the solvent contains less than the maximum amount of solute.

• Example: At 90℃, 30g of NaCl in 100g of H2O represents an unsaturated solution.

Solubility Curve - Supersaturated

• Any point above a line represents a supersaturated solution.

• In a supersaturated solution, the solvent contains more than the maximum amount of solute.

• Example: At 90℃, 50g of NaCl in 100g H2O represents a supersaturated solution

To read the graph:

1 - Find the line for the substance

2 - The amount that dissolves at a given temperature is on the y-axis

How much KNO₃ dissolves in 100g H₂O at 50℃

1. Find the line for KNO₃ (red)
2. Find the temperature and follow up to the line for KNO₃ (green)
3. Read across to the y-axis and this is the answer (blue)
4. About 87g of KNO3 will dissolve