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Reactions of Acids

Reactions of Acids. Neutralisation A neutral substance has a ph =7 . It contains equal numbers of H + and OH - Neutralisation is when we reduce the number of H + ions in an acid or reduce the number of OH - ions in an alkali – so that they become neutral. Neutralising Acids.

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Reactions of Acids

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  1. Reactions of Acids • Neutralisation • A neutral substance has a ph =7. It contains equal numbers of H+ and OH- • Neutralisation is when we reduce the number of H+ ions in an acid or reduce the number of OH- ions in an alkali – so that they become neutral.

  2. Neutralising Acids • If we add a BASE to and acid we can neutralise it. • There are 4 types of BASE: • Metals, Metal oxides, Metal hydroxides (soluble metal hydroxides are – alkali’s) and Metal Carbonates. • A new substance called a “salt” is always produced.

  3. Naming Salts • The first part of the name comes from the base – it will be a metal name. • The second part comes from the acid. • Salts usuallyend in “ ide” or “ ate

  4. Bases • Metals • Metal + Acid —>Salt + Hydrogen Example • Magnesium + Hydrochloric Acid —> Magnesiumchloride ( salt) + Hydrogen

  5. Metal oxides • Metal oxide + Acid —> Salt + Water Example Magnesium oxide + Carbonic Acid—> Magnesiumcarbonate + Water (salt)

  6. Metal hydroxide ( alkali) • Metal hydroxide + Acid —> Salt + Water Example Calcium hydroxide + Nitric Acid—> Calciumnitrate + Water

  7. Metal carbonate • Metal carbonate + Acid —> Salt + Water + Carbon dioxide Example Sodium carbonate + Sulphuric Acid—> Sodium sulphate + Water + Carbon dioxide

  8. Ionic Equations • Step 1. • Write down normal balanced equation, remember to use valency to work out formula of compounds. • Step 2 • Put in the charges of the ions in the ionic compounds in the equations – remember – covalent compounds e.g. Water don’t have ions!

  9. Example of Ionic Equation Calcium oxide + Hydrochloric Acid —> Calcium chloride + Water Step 1 Ca O + H Cl —> Ca Cl2+ H2O Step 2 Ca 2+ O 2- + H+ Cl- —> Ca 2+ (Cl-)2 + H2O(l)

  10. Spectator Ions • These are ions which do not change during the reaction – they are exactly the same on the left and fight side of the arrow! Example H+CL- + Na+ OH-—> Na+ Cl- + H2O The Na+ and Cl- ions have not changed – they are the spectator ions in this reaction.

  11. Making Insoluble Salts • We can make an insoluble salt when we mix certain salt solutions. • This is called Precipitation! • Use p5 in Data booklet to check solubility of compounds! • Example • Barium nitrate(s) + Sodium sulphate(s) • They swap partners- Barium sulphate(i) and Sodium nitrate(s) are formed. Barium sulphate is insoluble – it is a precipitate!

  12. Volumetric Titrations • This is when we work out the volume or concentration of an acid or alkali required for a neutralisation reaction. • C1 V1 = C2 V2 • C1 = Concentration of Acid • V1 = Volume of Acid • C1 = Concentration of Alkali • V1 = Volume of Alkali

  13. Examples! • Calculate the concentration of acid required id 20 cm3 neutralises 20 cm3 of 2mol/l alkali. • C1 V1 = C2 V2 • We are wanting to calculate C1 • C1 = C2 V2 / V1 • C1 = 2 x 0.02/ 0.02 = 2 mol/l

  14. Example 2 • What volume of alkali, with a concentration of 3 mol/l, is required to neutralise 50 cm3 of 2 mol/l acid? • C1 V1 = C2 V2 • V2 = C1 V1 / C2 • = 2 x 0.05/ 3 = 0.03 Litres

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