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6. Chemical Equations + Tests for Anions

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Presentation on theme: "6. Chemical Equations + Tests for Anions"— Presentation transcript:

1 6. Chemical Equations + Tests for Anions

2 Syllabus

3 Chemical Reaction In a chemical reaction, elements react together to form a new compound A new substance is always formed when a chemical reaction occurs

4 Evidence of a Reaction

5 Evidence of a Reaction Effervescence (gas) Colour change
Temperature change Light given off Noise given off Precipitate formation

6 Balancing Chemical Equations
Law of Conservation of Mass The total mass of the products of a chemical reaction is the same as the total mass of the reactants Law of Conservation of Matter Matter is neither created nor destroyed but merely changed from one form into another

7 Balancing Chemical Equations
CH O CO H2O Left hand side of equation = right hand side of equation Left Right C atom 1 H atom 4 2 O atom 3

8 Balancing Chemical Equations
2 2 CH O CO H2O Left hand side of equation = right hand side of equation Left Right C atom 1 H atom 4 2 O atom 3

9 Balancing Chemical Equations
2 CH O CO H2O Left hand side of equation = right hand side of equation Left Right C atom 1 H atom 4 O atom 3

10 Tests for Anions in Aqueous Solution
Ion= a charged atom or group of atoms Anion = a negative ion e.g.: Cl-, OH- Cation = a positive ion e.g.: Na+

11 Tests for Anions in Aqueous Solution
Chloride Cl- Sulfate SO42- Sulfite SO32- Carbonate CO32- Hydrogen carbonate HCO3- Nitrate NO3- Phosphate PO4 3-

12 Tests for Anions in Aqueous Solution
Chloride Sulfate Sulfite Carbonate Hydrogen carbonate Nitrate Phosphate

13 Tests for Anions in Aqueous Solution
Qualitative Analysis The identification of constituents present in a substance

14

15

16 Tests for Anions in Aqueous Solution
Test for Carbonate (CO32-) and Hydrogencarbonate (HCO3-) Dil HCl Effervescence observed: CO2 produced CO H+ -> CO H2O HCO H+ -> CO H2O Carbonate or hydrogencarbonate + dil HCl Bubbles!! Limewater

17 A solid material that settles out of solution
Tests for Anions in Aqueous Solution Precipitate A solid material that settles out of solution Test for Carbonate (CO32-) and Hydrogencarbonate (HCO3-) To distinguish between carbonates and hydrogen carbonates Magnesium Sulphate (MgSO4) Carbonate: white precipitate formed Mg CO > MgCO3 (insoluble) Hydrogen carbonate: no precipitate Mg HCO3- -> Mg(HCO3) Magnesium carbonate is insoluble in water Magnesium hydrogencarbonate is soluble in water

18 Tests for Anions in Aqueous Solution
Test for Carbonate (CO32-) and Hydrogencarbonate (HCO3-) Fizzing: CO H+ -> CO H2O White precipitate: Mg CO > MgCO3 ↓ Dil HCl MgSO4 CO32- Dil HCl Clear solution: Mg HCO3- -> Mg(HCO3)2 (sol) Fizzing: HCO H+ -> CO H2O MgSO4 HCO3-

19 Nitrate test also called the ‘Brown Ring’ Test
Tests for Anions in Aqueous Solution Nitrate test also called the ‘Brown Ring’ Test Test for Nitrate (NO3-) Iron sulphate (FeSO4) Conc sulphuric acid (H2SO4): N.B: test tube tilted and H2SO4 added slowly down the side of the test tube so that 2 layers are formed Brown ring formed at the junction of the 2 layers

20 Tests for Anions in Aqueous Solution
Test for Nitrate (NO3-) NO3- + FeSO4 Conc. H2SO4 2 layers Brown ring formed between the layers

21 A solid material that settles out of solution
Tests for Anions in Aqueous Solution Precipitate A solid material that settles out of solution Test for Phosphate (PO43-) Ammonium molybdate: (NH4)2MoO4 Conc nitric acid (HNO3) Placed in warm water Yellow precipitate

22 Tests for Anions in Aqueous Solution
Test for Phosphate (PO43-) PO43- + Ammonium molybdate Conc. HNO3 Place in warm water Yellow ppt

23 A solid material that settles out of solution
Tests for Anions in Aqueous Solution Precipitate A solid material that settles out of solution Test for Chloride (Cl-) Silver nitrate (AgNO3) White precipitate formed: Ag+ + Cl- -> AgCl Silver Chloride Silver chloride is insoluble in water To confirm silver chloride: add dilute ammonia solution and cloudiness disappears

24 Tests for Anions in Aqueous Solution
Test for Chloride (Cl-) Cl- + AgNO3 White ppt: AgCl

25 Tests for Anions in Aqueous Solution
Test for Sulfate (SO42-) and Sulfite (SO32-) Barium Chloride (BaCl) White precipitate formed in both: Ba SO42- -> BaSO4 Ba SO > BaSO3 Both barium sulfate and sulfite are insoluble in water Barium Sulfate Barium Sulfite

26 Tests for Anions in Aqueous Solution
Test for Sulfate (SO42-) and Sulfite (SO32-) To distinguish between sulfate and sulphite ions: Dil HCl Sulfate: precipitate remains (no reaction ) BaSO4 + HCl -> no reaction Sulfite: precipitate dissolves (cleat solution) SO H+ -> SO H2O Barium Sulfate is insoluble in HCl Barium Sulfite is soluble in HCl

27 Tests for Anions in Aqueous Solution
Test for Sulfate (SO42-) and Sulfite (SO32-) BaSO4 Dil HCl SO42- White ppt Ba SO42- -> BaSO4 ↓ No reaction (ppt remains): BaSO4 + HCl -> no reaction BaSO4 White ppt Ba SO > BaSO3 ↓ Dil HCl Clear solution (ppt dissolves) SO H+ -> SO H2O SO32-

28 Outline 2 assumptions of daltons atomic theory
Who discovered cathode rays How did Thompson discover the electron Describe the plum pudding model How was the nucleus discovered

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