Do Now - mchem.weebly.com

Do Now - mchem.weebly.com

Do Now 1. How many possible reactions are there when Group 1 and 2 elements react with Group 7? 2. Which reaction would be the most reactive of them all? 3. Which reaction would be the least reactive of them all? 4. a) What would be produced when lithium reacts with chlorine? b) What is being oxidised in this reaction? c) What is being reduced in this reaction? 5. a) What would be produced when barium reacts with bromine? b) What is being oxidised in this reaction? c) What is being reduced in this reaction> Experiment What did we discover? Question 1: a) No

b) Iodide ion yes but chloride ion no c) Yes Question 2: Cl2(aq) + 2Br-(aq) 2Cl-(aq) + Br2(aq) Cl2(aq) + 2I-(aq) 2Cl-(aq) + I2(aq) Br2(aq) + 2I-(aq) 2Br-(aq) + I2(aq) Colours when cyclohexane added Chlorine pale green colour does not change much Bromine orange colour looks a bit darker Iodine changes to purple/violet colour Chlorine water Initial colour

1 Bromine water Iodine solution Pale yellow-green to colourless Yellow-orange to colourless Yellow Upper

Purple Purple Lower Brown Orange/Brown Upper Orange Purple

Lower Orange Brown Colour after shaking with KI solution Colour of each layer after shaking with hexane Conclusion Iodine less reactive 2 Colour after shaking with KBr solution Colour of each layer after shaking with hexane

Conclusion Bromine is less than chlorine, more than iodine 3 Colour after shaking with KCl solution Colour of each layer after shaking with hexane Conclusion Chlorine is more reactive Upper Orange Purple

Lower Brown Brown Cl2(aq) Br2(aq) I2(aq) Cl(aq) Br(aq)

I(aq) www.chemsheets.co.uk AS 035 10-Jul-12 Cl2(aq) Cl(aq) Br2(aq) I2(aq)

Stays yellow solution (no reaction) Br(aq) I(aq) www.chemsheets.co.uk AS 035 10-Jul-12 Cl2(aq)

Cl(aq) Br2(aq) I2(aq) Stays yellow solution (no reaction) Stays brown solution (no reaction) Br(aq) I(aq)

www.chemsheets.co.uk AS 035 10-Jul-12 Cl2(aq) Cl(aq) Br(aq) Br2(aq) I2(aq)

Stays yellow solution (no reaction) Stays brown solution (no reaction) Yellow solution forms (Br2 forms) Cl2 + 2 Br- 2 Cl- + Br2 I(aq) www.chemsheets.co.uk AS 035

10-Jul-12 Cl2(aq) Cl(aq) Br(aq) Yellow solution forms (Br2 forms) Cl2 + 2 Br- 2 Cl- + Br2 Br2(aq) I2(aq)

Stays yellow solution (no reaction) Stays brown solution (no reaction) Stays brown solution (no reaction) I(aq) www.chemsheets.co.uk AS 035 10-Jul-12

Cl2(aq) Cl(aq) Br(aq) Yellow solution forms (Br2 forms) Cl2 + 2 Br- 2 Cl- + Br2 I(aq) Br2(aq) I2(aq)

Stays yellow solution (no reaction) Stays brown solution (no reaction) Stays brown solution (no reaction) Brown solution forms (I2 forms) Cl2 + 2 I- 2 Cl- + I2 www.chemsheets.co.uk

AS 035 10-Jul-12 Cl2(aq) Cl(aq) Br(aq) Br2(aq) I2(aq) Stays yellow solution (no reaction)

Stays brown solution (no reaction) Yellow solution forms (Br2 forms) Stays brown solution (no reaction) Cl2 + 2 Br- 2 Cl- + Br2 I(aq) Brown solution forms (I2 forms)

Cl2 + 2 I- 2 Cl- + I2 Brown solution forms (I2 forms) Br2 + 2 I- 2 Br- + I2 www.chemsheets.co.uk AS 035 10-Jul-12 What is an oxidising agent? Displacement Reactions and Oxidising Power of Halogens

Cl2(aq) + 2KBr(aq) Br2(aq) + 2KCl(aq) Oxidising power trend: Cl2 > Br2 > I2 When a halogen acts as an oxidising agent, it gains electrons (taken from the oxidised species). Cl Br I X2 + 2 e- 2 XDown the group it becomes harder to gain an electron because: atoms are larger & there is more shielding (due to extra electron shell)

Explain why chlorine can displace both bromine and iodine Chlorine has the strongest oxidising power. The increased shielding of extra shells reduces the effect of the increasing nuclear charge down the group. Since the chlorine has the smallest atomic radius it can accept electrons easier as they can get closer to the nucleus. Finisher for 10! Disproportionation reactions of chlorine One element undergoes both oxidation and reduction at the same time. Cl2 + H2O HCl + HClO

HCl hydrochloric acid HClO chloric(I) acid Both colourless solutions Disproportionation reactions of chlorine One element undergoes both oxidation and reduction at the same time. Chlorine with cold alkali Cl2 + 2NaOH NaCl + NaClO + H2O NaClO sodium chlorate(I) Disproportionation reactions of chlorine One element undergoes both oxidation and reduction at the same time. Chlorine with hot concentrated alkali 3Cl2 + 6NaOH 5NaCl + NaClO3 + 3H2O

NaClO3 sodium chlorate (V) Summary Questions Write equation and name the products of the reactions between bromine and: a) Cold dilute aqueous sodium hydroxide b) Hot concentrated sodium hydroxide solution Summary Questions Write equation and name the products of the reactions between bromine and: a) Br2 + 2NaOH NaBr + NaBrO + H2O b) 3Br2 + 6NaOH 5NaBr + NaBrO3 + 3H2O

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