Acids, Bases and Salts Edexcel Chemistry

Edexcel International GCSE Chemistry, Acids, Bases and salts Preparation

1. Acids, Bases and Salts Edexcel IGCSE Chapter 17

2. PH scale and indicator ACIDIC neutral ALKALINE Very Slightly Slightly Very 1 2 3 4 5 6 7 8 9 10 11 12 13 14 The pH scale is a measure of how acidic or alkaline a solution is. A substance forms an aqueous solution when it dissolves in water. Water itself is neutral. When substances dissolve in water, they dissociate into individual ions.

3. Water, H 2 O H + ( aq ) OH - ( aq ) hydrogen ion hydroxide ion acid alkali

4. Indicators Indicators are special dyes that change colour according to whether they are in acidic, alkaline or neutral solutions. Three common indicators are: Litmus Phenolphthalein Methyl Orange

5. Salt Formation The general equation is: Acid + Base  Salt + Water This is known as a neutralisation reaction because the products are neutral.

6. Salts consist of two parts – a metal part, and the non-metal ion from the acid. Acid Ions in solution Salts formed Hydrochloric acid H + Cl - chlorides Sulphuric acid 2H + SO 4 2- sulphates Nitric acid H + NO 3 - nitrates

7. Acids + Metals Acid + Metal  Salt + Hydrogen Magnesium + Hydrochloric  Magnesium + Hydrogen Acid chloride Mg + 2HCl  MgCl 2 + H 2

8. Acids + Metals Magnesium + Sulphuric Acid  Iron + Hydrochloric Acid  Lead + Sulphuric Acid 

9. Acids + Metal oxides Acid + Metal oxide  Salt + Water Magnesium + Hydrochloric Acid  Magnesium + Water oxide chloride

10. Questions ………… What is the formula of the following salts? Sodium bromide Magnesium fluoride Potassium nitrate Aluminium sulfate Write a balanced symbol equation, including state symbols, for the reaction of lithium oxide (in excess) with dilute sulfuric acid. Describe, in detail, how you could prepare a sample of copper sulfate crystals from its solution.

11. Answers ……… What is the formula of the following salts? Sodium bromide - NaBr Magnesium fluoride - MgF 2 Potassium nitrate - KNO 3 Aluminium sulfate - Al 2 (SO 4 ) 3 Write a balanced symbol equation, including state symbols, for the reaction of lithium oxide (in excess) with dilute sulfuric acid. Li 2 O + H 2 SO 4 → Li 2 SO 4 + H 2 O Describe, in detail, how you could prepare a sample of copper sulfate crystals from its solution. Measure out a volume of sulfuric acid ( eg. 50cm 3 ). Add copper oxide until it stops reacting (you will see insoluble copper oxide in the beaker). Heat gently to increase the rate of reaction. Filter out the unreacted copper oxide. Warm the copper sulfate solution in an evaporating basin (over a steam bath or using a water bath) to evaporate the water (crystallisation). Pour onto filter paper to finish drying.

12. Acids + Metal carbonate Acid + Metal  Salt + Carbon + Water carbonate dioxide Copper + Hydrochloric  Copper + Carbon + Water Carbonate acid chloride dioxide CuCO 3 + 2HCl  CuCl 2 + CO 2 + H 2 O

13. Metal + acid → salt + water + carbon carbonate dioxide calcium + hydrochloric → calcium + water + carbon carbonate acid chloride dioxide CaCO 3(s) + 2HCl ( aq ) → CaCl 2( aq ) + H 2 O (l) + CO 2(g)

14. Complete the word equations Magnesium carbonate + sulfuric acid → Zinc carbonate + sulfuric acid → Iron (II) carbonate + sulfuric acid → Sodium hydroxide + hydrochloric acid → Lithium hydroxide + hydrochloric acid → Ammonia + nitric acid → Potassium hydroxide + nitric acid → Write the balanced symbol equations for each of these reactions, with state symbols.

15. Magnesium carbonate + sulfuric acid → Magnesium sulfate + water + carbon dioxide MgCO 3(s) + H 2 SO 4( aq ) → MgSO 4( aq ) + H 2 O (l) + CO 2(g) Zinc carbonate + sulfuric acid → Zinc sulfate + water + carbon dioxide ZnCO 3(s) + H 2 SO 4( aq ) → ZnSO 4( aq ) + H 2 O (l) + CO 2(g) Iron (II) carbonate + sulfuric acid → Iron (II) sulfate + water + carbon dioxide FeCO 3(s) + H 2 SO 4( aq ) → FeSO 4( aq ) + H 2 O (l) + CO 2(g) Sodium hydroxide + hydrochloric acid → Sodium chloride + water NaOH ( aq ) + HCl ( aq ) → NaCl ( aq ) + H 2 O (l) Lithium hydroxide + hydrochloric acid → Lithium chloride + water LiOH ( aq ) + HCl ( aq ) → LiCl ( aq ) + H 2 O (l) Ammonia + nitric acid → Ammonium nitrate NH 3( aq ) + HNO 3( aq ) → NH 4 NO 3( aq ) Potassium hydroxide + nitric acid → Potassium nitrate + water KOH ( aq ) + HNO 3( aq ) → KNO 3( aq ) + H 2 O (l)

16. Solubility of salts If a substance is soluble , then this means that it will dissolve in a solvent. The most common solvent you will come across is WATER. Solute (the solid) + Solvent (water)  Solution (aqueous)

17. Eg. the preparation of sodium chloride by neutralization Dilute sodium hydroxide + indicator solution Dilute hydrochloric acid Preparing soluble salts from acids

18. Eg. the preparation of sodium chloride by neutralization Decolourising charcoal Filtrate Evaporating basin Preparing soluble salts from acids

19. Eg. the preparation of sodium chloride by neutralization Bunsen burner Water bath Steam Filtrate Acid + Alkali . Salt + Water HCl ( aq ) + NaOH ( aq )  NaCl ( aq ) + Water (l) Crystals of sodium chloride forming) Preparing soluble salts from acids

20. Preparing insoluble salts using precipitation reactions Eg. the preparation of lead iodide Lead nitrate Potassium iodide Yellow precipitate of lead iodide

21. Lead iodide Filter to separate the precipitate. Wash with distilled water and dry to get the pure product. Salt + Salt  Insoluble + Soluble salt salt Lead +. Potassium  Lead + Potassium nitrate iodide iodide nitrate Pb (NO 3 ) 2( aq ) + 2KI ( aq )  PbI (s) +. 2KNO 3( aq ) Preparing insoluble salts using precipitation reactions