The document details two types of chemical reactions: neutralisation (acid-base reactions) and precipitation, suitable for upper secondary students. It explains neutralisation through the interaction of acids and bases leading to the formation of water, and provides examples, including reactions with different compounds. Additionally, it discusses precipitation reactions that produce insoluble compounds from soluble ones, highlighting examples involving silver and barium salts.

1. TYPES OF REACTION Neutralisation or Acid-Base Precipitation Redox Suitable for Upper Secondary Students Author: Toh Chui Hoon

2. NEUTRALISATION A reaction between an acid and a base . In this reaction, the acid donates a hydrogen ion (H + or proton) to the base leading to formation of water . Examples of base : Oxides, Hydroxides and Carbonates Examples of acid : Hydrochloric acid, Sulphuric acid and Nitric acid

3. Examples of Neutralisation Acid + Oxide 2HCl + Cu O  CuCl 2 + H 2 O Acid + Hydroxide H 2 SO 4 + 2Na OH  Na 2 SO 4 + 2H 2 O Acid + Carbonate 2HNO 3 + Ca CO 3  Ca(NO 3 ) 2 + H 2 O + CO 2 Gives a H + to O 2- of CuO to form H 2 O

4. QUIZ Which of the following basic ions can be identified using products from acid-base reaction? A : OH - B : O 2- C : CO 3 2- D : Cl - ANSWER : Yes, it is C . When acid is added to carbonates, bubbling or effervescence can be seen due to production of CO 2 gas which will turn limewater, Ca(OH) 2 , cloudy. This is caused by production of CaCO 3 as a result of acid-base reaction between aqueous CO 2 and Ca(OH) 2 . Ca(OH) 2 + CO 2  CaCO 3 + H 2 O Hint: There must visible change in the reaction.

5. PRECIPITATION This reaction involves 2 water-soluble compounds leading to formation of a water-insoluble compound . Examples of water-soluble compounds : all Nitrates, most Sulphates except BaSO 4 and PbSO 4 , most Chlorides except AgCl and PbCl 2 . Examples of water-insoluble compounds : Oxides, Hydroxides and Carbonates except those of Na + , K + and NH 4 + .

6. Coloured Compounds Compounds containing transition metal ions are coloured. Copper sulphate, CuSO 4 is blue . Iron(II) hydroxide, Fe(OH) 2 is dirty-green . Iron(III) hydroxide, Fe(OH) 3 is reddish-brown . Potassium dichromate(VI), K 2 Cr 2 O 7 is orange . Potassium manganate(VII), KMnO 4 is violet .

7. Examples of Precipitation HCl(aq) + AgNO 3 (aq)  AgCl(s) + HNO 3 (aq) A white precipitate of silver chloride is seen. On further addition of aqueous NH 3 , silver chloride dissolved . After excess aq. NH 3 is added…

8. Examples of Precipitation KI(aq) + AgNO 3 (aq)  AgI(s) + KNO 3 (aq) A yellow precipitate of silver iodide is seen.

9. Examples of Precipitation Na 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq)  BaSO 4 (s) + 2NaNO 3 (aq) A white precipitate of barium sulphate is seen.

10. Examples of Precipitation H 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq)  BaSO 4 (s) + HNO 3 (aq) A white precipitate of barium sulphate is seen.