Title: Acids and bases Complete the activities listed below 28/08/2019 Lesson aim: Describe reactions between acids and alkalis, understand how salts are formed and how to name them. Use the above pH chart to describe how acidity (how acidic something is) and alkalinity (how alkaline something is) changes with pH. The lower the pH, the greater the acidity (the lower the alkalinity). The higher the pH, the lower the acidity (greater the alkalinity). Key words: Acid, alkali, hydrogen ion, salt, neutralisation.

Open your workbook to page 81 Work through pages 83-89 by yourselves.

Some key terms: 28/08/2019 Acid: Base: a substance that releases hydrogen ions (H+) ions when dissolved in water. The hydrogen ions (H+) make the solution acidic. Have a pH of less than 7. Strong acids include: sulphuric acid, nitric acid and hydrochloric acid. Base: Bases react with acids to neutralise them. Bases that can dissolve in water are called alkalis. They release hydroxide ions (OH-) into solution. These give alkalinity. They have a pH greater than 7.

Strength of acids and alkalis 28/08/2019 Strong acids release high concentrations of H+ ions. Weak acids release low concentrations of H+ ions. Strong alkalis release high concentrations of OH- ions. Weak alkalis release low concentrations of OH- ions.

H+(aq) + OH-(aq)  H2O(l). Neutralisation 28/08/2019 This happens when acids and alkalis react together: Products of this reaction: Salt and water. Ionic equation that describes neutralisation: H+(aq) + OH-(aq)  H2O(l). State symbols: (s) = Solid state e.g. Mg(s), CaCO3(s), CaO(s) (l) = Liquid state e.g. H2O(l) (g) = Gas state e.g. O2(g), CO2(g) (aq) = Aqueous state (dissolved in water) e.g. NaOH(aq), HCl(aq) Try question pages 83-84

Neutralisation: Making Salts 28/08/2019 Neutralisation: Making Salts A salt’s name has 2 parts: e.g. Magnesium chloride. The magnesium part comes from the metal or alkali that is reacting. E.g. Magnesium/Magnesium oxide/Magnesium hydroxide. The chloride part comes from the acid that reacts. Different acids give different suffixes! Name of acid used Suffix used for salt name Hydrochloric _____________Chloride Sulfuric _____________Sulfate Nitric _____________Nitrate Phosphoric _____________Phosphate Name the salts made from reacting magnesium hydroxide with each of the acids in the table above.

Suffix used for salt name Name the salt! 28/08/2019 Sodium oxide + nitric acid: Potassium + phosphoric acid: Calcium oxide + hydrochloric acid: Lithium + sulfuric acid: Name of acid used Suffix used for salt name Hydrochloric _____________Chloride Sulfuric _____________Sulfate Nitric _____________Nitrate Phosphoric _____________Phosphate Sodium Nitrate Potassium phosphate Calcium chloride Lithium sulfate

You get given all of these formulae on a data sheet! 28/08/2019 Now try the formulae! Sodium Nitrate NaNO3 Calcium chloride CaCl2 Lithium sulfate Li2SO4 You get given all of these formulae on a data sheet!

Other products 28/08/2019 As well as the salt, other products can form: When reacting acid with a metal: The salt and HYDROGEN GAS (H2(g)) form. E.g. Sodium + hydrochloric acid  Sodium chloride + hydrogen. When reacting acid with a metal oxide: The salt and WATER (H2O(l)) form. E.g. Sodium oxide + hydrochloric acid  Sodium chloride + Water. When reacting acid with carbonates (e.g. CaCO3(s)): The salt and CARBON DIOXIDE (CO2(g)) AND WATER(H2O(l)) form. E.g. Sodium carbonate + hydrochloric acid  Sodium chloride + carbon dioxide + water Write symbolic equations for the word equations given above.

Other products 28/08/2019 As well as the salt, other products can form: When reacting acid with a metal: 2Na(s) + 2HCl(aq)  2NaCl(aq) + H2(g) E.g. Sodium + hydrochloric acid  Sodium chloride + hydrogen. When reacting acid with a metal oxide: Na2O(s) + 2HCl(aq)  2NaCl(aq) + H2O(l) E.g. Sodium oxide + hydrochloric acid  Sodium chloride + Water. When reacting acid with carbonates (e.g. CaCO3(s)): Na2CO3(s) + 2HCl(aq)  2NaCl(aq) + H2O(l) + CO2(g) E.g. Sodium carbonate + hydrochloric acid  Sodium chloride + carbon dioxide + water Write symbolic equations for the word equations given above.

Questions 28/08/2019 Name the salt formed when nitric acid reacts with: Magnesium. Copper oxide. Making potassium chloride using potassium metal forms hydrogen gas as a by-product. Using potassium oxide forms water. Which method is safer to use? Explain. Zinc nitrate [Zn(NO3)2] can be made by reacting nitric acid [HNO3] and zinc metal, or zinc oxide [ZnO]. Write word and balanced symbol equations for both reactions.

Questions 28/08/2019 Name the salt formed when nitric acid reacts with: Magnesium nitrate (+ hydrogen gas). Copper nitrate (+ water). Hydrogen gas is highly flammable/explosive. Water is a safe by-product that is easy to remove. Use potassium oxide. Zinc + nitric acid  zinc nitrate + hydrogen gas. Zn + 2HNO3  Zn(NO3)2 + H2 Zinc oxide + nitric acid  zinc nitrate + water. ZnO + 2HNO3  Zn(NO3)2 + H2O

Making salts: Put the method in the correct order 28/08/2019 Gently swirl the contents to mix, and then pour into the filter paper in the funnel. Allow to filter through. Place the filter funnel and fluted filter paper in the neck of the conical flask. Add small portions of copper(II) oxide to the beaker. A clear blue solution should collect in the flask. If the solution is not clear, and black powder remains in it, you will need to repeat the filtration. Stir the mixture gently for up to half a minute after each addition. Keep doing this until excess copper oxide remains at the bottom. Allow the beaker to cool slightly. Add 20 cm3 of the heated 0.5 M sulfuric acid to the 100 cm3 beaker.

Making Copper Sulfate: The Method 28/08/2019 Add 20 cm3 of the 0.5 M sulfuric acid to the 100 cm3 beaker. Use a spatula to add small portions of copper(II) oxide to the beaker. Stir the mixture gently for up to half a minute after each addition. Keep doing this until excess copper oxide remains at the bottom. Allow the beaker to cool slightly while you set up Stage 2. Place the filter funnel and fluted filter paper in the neck of the conical flask. Gently swirl the contents to mix, and then pour into the filter paper in the funnel. Allow to filter through. A clear blue solution should collect in the flask. If the solution is not clear, and black powder remains in it, you will need to repeat the filtration.

Insoluble salts: a.k.a “Precipitates” 28/08/2019 A precipitate is formed when 2 solutions of different soluble salts are reacted together. A displacement reaction takes place forming 1 new soluble salt and 1 new insoluble salt – a precipitate. E.G. Calcium nitrate + sodium carbonate  Calcium carbonate + sodium nitrate Ca(NO3)2(aq) + Na2CO3(aq)  CaCO3(s) + 2NaNO3(aq) (aq) = “Aqueous” [dissolved in water] (s) = Solid

Demo: Formation of Lead Iodide 28/08/2019 Mix together the 2 soluble salts. Swirl. Allow the precipitate to settle. Filter the mixture. Wash with water. Allow to dry.

Salts that are soluble in water Salts that are insoluble in water All salts containing sodium, potassium and ammonium ions. - All salts containing nitrate ions. Most chloride, bromide and iodide salts Lead chloride/bromide/iodide. Silver chloride/bromide/iodide. Most Sulfates. Sulfates of: barium, calcium and lead. Carbonates containing sodium, potassium and ammonium ions. Most other carbonates (assume the only soluble carbonates are in the left column). Hydroxides containing sodium, potassium and ammonium ions. Most other hydroxides (assume the only soluble hydroxides are in the left column).

Questions 28/08/2019 Using your table, identify 3 soluble salts and 3 insoluble salts. Explain what a precipitate is and how one is made. Write a word equation for the reaction between ammonium sulfate and lead nitrate. Name the precipitate formed. Sketch a series of diagrams that contains particles to show how a precipitate is formed from 2 soluble salts.