C. Johannesson

The Nature of Solutions

Ch. 12- Solutions

C. Johannesson

A. Definitions

• Solution - homogeneous mixture

Solvent - present in greater amount

Solute - substance being dissolved

C. Johannesson

B. Solvation

• Ionization– breaking apart of

some polar molecules into aqueous ions

HNO3(aq) + H2O(l) H3O+(aq) + NO3–(aq)

C. Johannesson

B. Solvation

• Dissociation– separation of an ionic

solid into aqueous ions

NaCl(s) Na+(aq) + Cl–(aq)

Making solutions• Whether the solute and the solvent are

polar, nonpolar, or ionic determines– How much will dissolve.– Whether a substance will dissolve.

How Much?• Dissolved particles are surrounded by

solvent particles• Eventually solvent particles are all occupied • Begin turning back to solid• Equilibrium reached where dissolved

particles are turning to solid as fast as solid is being dissolved

• No more will dissolve

How Much?• Solubility- The maximum amount of

substance that will dissolve at that temperature (usually g/L).

• Saturated solution- Contains the maximum amount of solid that can be dissolved.

• Unsaturated solution- Can dissolve more solute.

• Supersaturated- A solution that is temporarily holding more than it can, a seed crystal will make it come out

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C. Solubility

SATURATED SOLUTIONno more solute dissolves

UNSATURATED SOLUTIONmore solutedissolves

SUPERSATURATED SOLUTIONbecomes unstable, crystals form

concentration

C. Johannesson

C. Solubility

• Solubility Curve– shows the

dependence of solubility on temperature

Practice Problems

1. How many grams of potassium nitrate can dissolve in 100 g of water at 500C?

2. At 200C, a solution contains 120 g of NaNO3 in 100 g of water. Is this solution saturated, unsaturated, or supersaturated?

3. You need to make a solution containing 150 g of potassium chloride in 300 g of water. What temperature is required?

Liquids

• Miscible means that two liquids can dissolve in each other.

• Immiscible means they can’t

Why does Italian dressing separate?A) Oil and vinegar are immiscibleB) Oil is nonpolar and vinegar polarC) Vinegar particles are attracted to themselves

more than they are attracted to the oil particles.

D) All of the above