5.2 Salts

5.2 SaltsCan be formed several ways

• Acid – Base Neutralization• Oxides and carbonates

reacting with acid• Metal reacting with acid

Salts have many uses• Making batteries, explosives, fertilizers, multivitamin and mineral tablets, blood and urine, tree sap

Not just a flavour!

Magnesium acetate:

Mg(CH3COO)2

Table Salt:NaCl

Aluminum Sulfate:

Al2(SO4)3

Salts - Neutralization• A Salt results when an acid reacts

with a base. Both are neutralized. • The H+ and OH- ions combine to form

water.• The non-metallic ions of the acid and

the metal ions of the base form the salt.

• Acid + Base ----> Salt + Water• HCl + NaOH ----> NaCl + H2O• H2SO4 + Ca(OH)2 ----> CaSO4 + H2O

Metal and non-metal oxides

Metal oxide: a metal combined with oxygen

• Solution becomes basic when dissolved in water

• Na2O(s) + H2O (l) 2NaOH (aq)

Non-metal oxide: a non-metal combined with oxygen

• Solution becomes acidic when dissolved in water

• SO3 (g) + H2O (l) H2SO4 (aq)

Chemically combined with oxygen.

Acids and Metals

• When metals react with acids, they usually release hydrogen gas

• 2HCl (aq) + Mg (s) MgCl2(aq) + H2 (g)

The most reactive metals appear on the extreme left of the periodic table

online metals in acid demo

Acids and Carbonates• Carbonate (CO3) is trapped in rocks• When carbonate rocks react with

acids, the carbonates help neutralize the acid

• Liming is a process that people do to help neutralize acidic lakes.

• Liming adds calcium carbonate (CaCO3) to the lake. Very expensive.

• Carbonates reacting with acid release CO2

• H2SO4 + CaCO3 CaSO4 + H2O + CO2

Carbonate is a combination of carbon and oxygen

The Naked EggEggshells are made up of calcium carbonate

• CaCO3Vinegar is also called acetic acid (5%

solution)• CH3COOH• 5% acetic acid 95% waterThe chemical reaction is:2CH3COOH + CaCO3 Ca(CH3COO)2 + H2O + CO2

• The eggshell has been removed leaving the thin membrane called a semi-permeable membrane which water can pass through.

• What were the bubbles on the surface of the egg?• Think about the impact of acid rain on shells in nature!

The chemistry of removing an egg shell

The Naked EggBubbles of CO2Osmosis: water traveling through a membrane from a high concentration to a low concentration.

(c) McGraw Hill Ryerson 2007

5.2 Salts

• Salts are ionic compounds formed when acids and bases react. Salts are also produced when oxides or carbonates react with acids or when metals

react with acids.• Table salt, NaCl, is found in sea water, salt lakes or rock deposits.

Salt was once very valuable as a commodity. Iodine is now added to salt to minimize goiter (a disease of the thyroid).

• NaCl is only one kind of salt. A salt is made up of a positive ion

from a base and a negative ion from an acid.

Salts are found in many things: In batteries, explosives and fertilizers In multivitamins In many living cells

See pages 234 - 235

Salt crystals in Death Valley

(c) McGraw Hill Ryerson 2007

Acid-Base Neutralization, andMetal Oxides and Non-Metal Oxides

• Neutralization reactions occur when an acid and a base react to produce a salt and water. HCl(aq) + NaOH(aq) NaCl(s) + H2O(l)

acid base salt water

• Metal oxides react with water to form bases. Na2O(s) + H2O(l) 2NaOH(aq)

• Non-metal oxides react with water to form acids SO2(g) + H2O(l) H2SO3(aq) Non-metal oxides are formed from the burning of fossil fuels.

Acid added to water in the atmosphere = acid precipitation.

See pages 236 - 237

The effects of acid rain on a forest

(c) McGraw Hill Ryerson 2007

Acids and Metals, andAcids and Carbonates

• Acids and Metals The most reactive metals, at the bottom of groups 1 and 2 on the periodic

table, react vigorously with water and acids. All other metals are less reactive than those in groups 1 and 2. When metals do react with acids, H2 gas is usually released. 2HCl(aq) + Mg(s) MgCl2(s) + H2(g)

• Acids and Carbonates Carbonates neutralize acids, protecting locations with natural carbonate

supplies from acid precipitation. H2SO4(aq) + CaCO3(s) CaSO4(s) + H2O(l) + CO2(g)

sulphuric calcium calcium water carbonacid carbonate sulphate dioxide

See pages 238 - 239Take the Section 5.2 Quiz