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Acids and Bases (2)

Acids and Bases (2). Do you know?. Acid Bath Murder http://www.discoverychannel.co.uk/web/crime-museum-uk/episode-guide/acid-bath-murder/. Uses of Acids. Sulphuric acid: Making detergents Making fertilisers In car batteries. Hydrochloric acid: In leather processing

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Acids and Bases (2)

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  1. Acids and Bases (2)

  2. Do you know? Acid Bath Murder http://www.discoverychannel.co.uk/web/crime-museum-uk/episode-guide/acid-bath-murder/

  3. Uses of Acids • Sulphuric acid: • Making detergents • Making fertilisers • In car batteries • Hydrochloric acid: • In leather processing • For cleaning metals • Ethanoic acid: • (In vinegar) to preserve food • In making adhesives such as glue

  4. The Definition of an Acid An acid is a substance that produces hydrogen ions, H+ (aq) in water.

  5. The Role of Water in Acids • Acids only show the properties of acids when they are dissolved in water.

  6. The Role of Water in Acids • Acids only show the properties of acids when they are dissolved in water. Exists as molecules when dissolved in organic solvents like alcohol HCl dissociates into H+ and Cl- when dissolved in water

  7. The Role of Water in Acids • Acids dissociate in water to produce hydrogen ions which are responsible for the acidic properties. How about sulfuric acid and nitric acid? HCl (aq)  H+ (aq) + Cl- (aq)

  8. What really happens.. Reaction with metals 2H+ (aq) + Mg (s)  H2 (g) + Mg2+ (aq) The H+ ions (produced by HCl) allows acids to react with the metal, magnesium. Similarly, the H+ ions from the acid are responsible for the other reactions with carbonates, hydrodencarbonates, hydroxides and oxides. from HCl (aq)

  9. Ionic Equation An ionic equation is an equation involving ions in aqueous solution; only those ions formed or changed during the reaction are included.

  10. Basicity of an Acid • The maximum number of hydrogen ions produced by a molecule of an acid is called the basicity of the acid. E.g. Hydrochloric acid is monobasic. Sulfuric acid is dibasic. Can you think of a tribasic acid?

  11. Strong and Weak Acids Can you tell the difference?

  12. Strong Acid • A strong acid is one that completely ionises in water. • All acid molecules become ions in the water. • Examples of strong acid: • HCl (aq) • HNO3 (aq) • H2SO4 (aq) E.g. HCl (aq)  H+(aq) + Cl-(aq)

  13. Eg. CH3COOH (aq) CH3COO-(aq) + H+(aq) Weak Acid • A weak acid is one that partially ionises in water. • Most acid molecules remain unchanged in the water (99%) • Examples of weak acid: • Ethanoic acid CH3COOH • Citric acid C6H8O7 • Phosphoric acid H3PO4

  14. Reactivity of Strong and Weak Acids Would you expect the reactivity to be different? Yes, strong acids react more vigorously than weak acids.

  15. Strength VS Concentration

  16. Strength VS Concentration • ‘Strong’ does not mean ‘concentrated’. • ‘Weak’ does not mean ‘dilute’. • Strength refers to the extent to which the acid molecule dissociates when dissolved in water. • Concentration refers to the amount of solute in the solution.

  17. Concentration of Acid • The term concentration tells us how much of a substance is dissolved in 1 dm3 of a solution. • It can be changed, either by adding more solvent or solute. Adding solvent to make it dilute Adding solute to make it concentrated

  18. Strength VS Concentration Concentrated, strong acid Strong acid Dilute, strong acid Weak acid

  19. Strength of Acid • The strength of an acid can be shown on a pH scale.

  20. Ionic Equation In ionic equations: • Formulae of ions that change (react) are included; ions that do not change are omitted. • Formulae of solid, liquid, gases are written in full

  21. So, what have you learnt today?

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