How are salts made and named?

2. + acid base  a salt • The first part of the salt’s name comes from the base: e.g. sodium hydroxide sodium…  • The second part of the salt’s name comes from the acid: e.g. sulfuric acid sulfate…  How are salts made and named? When an acid reacts with a base, a neutralization reaction occurs and produces a chemical called a salt. The name of the salt depends on the names of the reactants. For example, if sodium hydroxide neutralizes sulfuric acid, the product is a salt called sodium sulfate.

3. What is the name of the salt?

4. What are salts used for? The colours of fireworks are formed when certain salts burn. Calcium chloride, for example, burns a bright red colour. Table salt is sodium chloride. This is the salt used to flavour and preserve food. Indigestion remedies often contain magnesium salts. Salts can also be used as coloured pigments in paints, and to help fuels burn better.

5. + + acid alkali  salt water hydrochloricacid sodiumhydroxide sodiumchloride + +  water + + NaCl (aq) HCl (aq) H2O (aq)  NaOH(aq) Making salts 1: acid + alkali When an acid reacts with an alkali, the products are a salt and water. Water is formed because OH– ions from the alkali react with H+ ions from the acid to produce molecules of water (H2O). For example:

6. hydrochloricacid sodiumhydroxide sodiumchloride + +  water + + NaCl (aq) HCl (aq) H2O (aq)  NaOH(aq) When is the reaction complete? The reaction between sodium hydroxide and hydrochloric acid produces sodium chloride, which is soluble in water. There is no obvious sign when this reaction is complete, so an indicator is used to show when the solution is neutral. This process is called titration.

7. What is a titration?

8. + + acid metal  a salt hydrogen hydrochloricacid zincchloride + + zinc  hydrogen + + ZnCl2(aq) 2HCl (aq) H2 (aq)  Zn (aq) Making salts 2: acid + metal When a metal is added to an acid, the products are a salt and hydrogen gas. For example: This method of making salts only works with some metals. What would happen if potassium was used? Or copper?

9. Which metal will react the most?

10. + + acid metal oxide  salt water calciumchloride hydrochloricacid calciumoxide + +  water + + CaCl2 (aq) 2HCl (aq) CaO(aq)  H2O (aq) Making salts 3: acid + metal oxide When a metal oxide is mixed with an acid, the products are a salt and water. Water forms because oxygen ions from the oxide join up with H+ ions from the acid to produce molecules of water (H2O). For example:

11. sulfuricacid copper oxide copper sulfate + +  water H2SO4 (aq) CuO (s) CuSO4 (aq) H2O (aq) Obtaining salts from metal oxides When a metal oxide is added to an acid, it dissolves as it reacts. You know when you have added enough of the metal oxide because it stops dissolving. How could the solid copper sulfate salt be separatedfrom the water?

12. Obtaining salts from copper oxide

13. carbon dioxide + + + acid carbonate  salt water coppernitrate carbondioxide nitricacid coppercarbonate + + +  water + + + Cu(NO3)2(aq) 2HNO3(aq) CuCO3(s)  H2O(aq) CO2(g) Making salts 4: acid + carbonate When a carbonateis mixed with an acid, the products are a salt, carbon dioxide and water. Water and carbon dioxide are formed because the carbonate ions (CO32-) react with H+ ions from the acid. For example: What would you expect to observe in this reaction?

14. acid + alkali a salt + water • acid + metal a salt + hydrogen • acid + metal oxide a salt + water • acid + carbonate a salt + carbon dioxide + water     Making salts – summary Salts can be made by reacting acids with bases. There are four ways of making salts from acids:

15. Matching reactants and salts

16. Complete the neutralization reaction

18. lead nitrate sodium chloride lead chloride sodium nitrate + +  + + Pb(NO3)2(aq) 2NaCl (aq)  PbCl2 (s) 2NaNO3 (aq) What is a precipitation reaction? Sometimes when two solutions are mixed, they react to form an insoluble solid product. The insoluble solid product is called a precipitate. You can spot a precipitate because the mixture goes cloudy. For example, mixing solutions of lead nitrate and sodium chloride produces a yellow precipitate of lead chloride.

19. sodium carbonate magnesium chloride sodium chloride magnesium carbonate + +  + + Na2CO3 (aq) MgCl2 (aq)  2NaCl (aq) MgCO3 (s) How can hard water be softened? Hard water contains magnesium and calcium ions, which can clog up pipes and heating elements. These ions can be removed using precipitation reactions. Sodium carbonate is added to the hard water to form precipitates, which can then be removed by filtration. The magnesium ions are removed by this reaction: What are the word and symbol equations for the removal of the calcium ions?

20. iron(III) chloride sodium hydroxide iron(III) hydroxide sodium chloride + +  + + FeCl3 (aq) 3NaOH (aq)  Fe(OH)3 (s) 3NaCl (aq) Precipitates of hydoxides Many metals form hydroxide precipitates, which have characteristic colours. For example, when sodium hydroxide solution is added to a solution of iron(III) chloride, the reaction produces a brown precipitate of iron(III) hydroxide.

21. Identifying precipitates

22. Identifying metals

23. Precipitation – true or false?

25. Glossary • acid – A substance that releases H+ ions in solution. • alkali – A substance that releases OH- ions in solution. • base – Any substance that reacts with an acid. • decomposition – A type of reaction in which a compound is broken down into two or more substances. • neutralization – A type of reaction in which an acid reacts with a base to produce a salt. • precipitate – A solid, insoluble product of a reaction. • precipitation – A type of reaction in which two aqueous solutions react to form an insoluble product. • salt – A substance formed when an acid reacts with a base. • titration – A method of indicating when an undetectable reaction, such as neutralization, is complete.

26. Anagrams

27. Completing equations

28. Multiple-choice quiz