Solutions, Acids, and Bases

Chapter 8

Section 8-1

• Formation of Solutions

Dissolving

• Substances can dissolve in water three ways:– Dissociation– Dispersion– Ionization

• Solute – what is being dissolved• Solvent – the substance in which

the solute dissolves

Dissociation

• Dissociation – process in which an ionic compound separates into ions as it dissolves.

Dispersion

• Dispersion – breaking into smaller pieces that spread throughout the water.

Ionization

• Ionization – the process in which neutral molecules gain or loose electrons (and form ions).

Properties of Liquid Solutions

• The three physical properties of a solution that can differ from those of its solute and solvent are – Conductivity– Freezing Point– Boiling Point

Heat of Solution

• During the formation of a solution, energy is either released or absorbed.

• The process is either endothermic or exothermic.

Rates of Dissolving

• Factors that affect the rate of dissolving include– Surface area– Stirring– Temperature

Section 8-2

• Solubility and Concentration

Solubility

• Solubility – the maximum amount of a solute that dissolves in a given amount of solvent.

• Solutions are described as saturated, unsaturated, or supersaturated depending on the amount of solute in solution.

Solubility

• Saturated solution – one that contains as much solute as the solvent can hold at a given temperature.

• Unsaturated Solution – a solution that has less than the maximum amount of solute that can be dissolved.

Solubility

• Supersaturated Solution – one that contains more solute than it can normally hold at a given temperature. These solutions are very unstable.

Factors Affecting Solubility

• The factors that affect the solubility of a solute are – Polarity of the solvent (like

dissolves like)– Temperature– Pressure

Concentration of Solutions

• Concentration can be expressed as– Percent by volume– Percent by mass– Molarity

Percent by Volume

Volume of soluteVolume of solution

x 100%

Percent by Mass

Mass of soluteMass of solution x 100%

Molarity

Molarity = Moles of soluteLiters of solution

Summary

• How are solutions with different amounts of solute described?

• What factors determine the solubility of a solute?

• What are three ways to measure the concentration of a solution?

Section 8-3

• Properties of Acids and Bases

Properties of Acids

• Some general properties of acids include– Sour taste– Reactivity with metals– Ability to produce color changes in

indicators• Indicator – any substance that

changes color in the presence of an acid or base.

Properties of Bases

• Some general properties of bases include– Bitter taste– Slippery feel– Ability to produce color changes in

indicators

Neutralization and Salts

• Neutralization – the reaction between an acid and a base.

• The neutralization reaction between an acid and a base produces a salt and water.

Neutralization and Salts

Example: HCl + NaOH NaCl + H2O

• Since all acids have H (hydrogen) ion and all bases have OH (hydroxide) ion, when the two mix, they make water and an ionic compound (known as a salt).

Proton Donors and Acceptors

• Acids can be defined as proton donors, and bases can be defined as proton acceptors.

How is an acid a proton donor?

All acids contain an H (hydrogen) ion.

+

e-

Summary• What are some general

properties of acids and bases?

• What are the products of neutralization?

• What are proton donors and proton acceptors?

Section 8-4

• Strength of Acids and Bases

The pH Scale

• The lower the pH value, the greater the H3O+ ion concentration.

• The higher the pH value, the lower the H3O+ ion concentration.

Strong Acids & Bases

• When strong acids dissolve in water, they ionize almost completely.

• Strong bases dissociate almost completely in water

Electrolytes

• Electrolyte – a substance that ionizes or dissociates into ions when it dissolves in water.

• Resulting solution can conduct electricity.

• Strong acids and bases are strong electrolytes because they dissociate or ionize almost completely in water.