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5.2 Salts

5.2 Salts. Table Salt: NaCl. Not just a flavour !. Can be formed several ways Acid – Base Neutralization Oxides and carbonates reacting with acid Metal reacting with acid Salts have many uses

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5.2 Salts

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  1. 5.2 Salts Table Salt: NaCl Not just a flavour! Can 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 Aluminum Sulfate: Al2(SO4)3 Magnesium acetate: Mg(CH3COO)2

  2. 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

  3. Metal and non-metal oxides Chemically combined with oxygen. 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)

  4. Acids and Metals The most reactive metals appear on the extreme left of the periodic table When metals react with acids, they usually release hydrogen gas 2HCl (aq) + Mg (s) MgCl2(aq) + H2 (g) online metals in acid demo

  5. Acids and Carbonates Carbonate is a combination of carbon and oxygen 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

  6. The Naked Egg The chemistry of removing an egg shell Eggshells are made up of calcium carbonate • CaCO3 Vinegar is also called acetic acid (5% solution) • CH3COOH • 5% acetic acid 95% water The 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!

  7. The Naked Egg Bubbles of CO2 Osmosis: water traveling through a membrane from a high concentration to a low concentration.

  8. 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 Salt crystals in Death Valley See pages 234 - 235 (c) McGraw Hill Ryerson 2007

  9. 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. The effects of acid rain on a forest See pages 236 - 237 (c) McGraw Hill Ryerson 2007

  10. 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 carbon acid carbonate sulphate dioxide See pages 238 - 239 Take the Section 5.2 Quiz (c) McGraw Hill Ryerson 2007

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