Chapter 8: reactivity trends

1st ionisation energy

The energy required to lose 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

trend of 1st ionisation energy down group 2

it decreases

What is formed when group 2 metal oxides react with water?

metal hydroxides (of which alkaline solutions are formed and hydroxide ions are released)

Are group 2 hydroxides soluble?

slightly, but will form precipitate if solution becomes too saturated

trend in solubility and pH of group 2 hydroxides going down group

increases

Fluorine appearance at RTP

pale yellow gas

Chlorine appearance at RTP

yellow gas

Bromine appearance at RTP

brown liquid

iodine appearance at RTP

grey solid (turns into purple gas)

Astatine appearance at RTP

black solid

what colour are halide ions?

colourless

colour of chlorine in water/cyclohexane

pale green

colour of bromine in water/cyclohexane?

orange

colour of iodine in water/cyclohexane?

brown in water

purple in cyclohexane

halogen reactivity trend down group

decreases

Reaction of Chlorine and water?

Cl2(aq) + H20(l) → HClO(aq) + HCl(aq)

Why is chlorine used to purify used to purify water?

chloric acid (HClO) and hydrochloric acid (HCl) kill bacteria

Disproportionation

a redox reaction where the same element is both oxidised and reduced

benefits of adding chlorine to water

ensures bacteria is killed so water is fit to drink

risks of adding chlorine to water

it’s a toxic respiratory irritant that can be fatal in large doses

chlorinated water can react with organic hydrocarbons to form chlorinated hydrocarbons suspected of being carcinogen)

4 types of reaction observations

effervescence

colour change

precipitates

gas identification

when are precipitates formed?

when 1 of the products of 2 solutions is insoluble

test for carbonates

add dilute acid to form carbon dioxide

test for sulfates

add dilute acid and then barium solution to form white precipitate (eg: barium nitrate if nitric acid is added)

test for halides

add dilute acid and then AgNO3 solution

if white ppt → chloride

cream ppt → bromide

yellow ppt → iodide

solubility of chloride with aqueous ammonia

soluble

solubility of bromide with aqueous ammonia

soluble

solubility of iodide with aqueous ammonia

insoluble

why is the halide test the last anion test carried out

silver carbonates and silver sulphates also make white ppt

ammonium test

add aqueous NaOH to solution and heat

test gas produced with damp pH paper (should turn blue as ammonia is alkaline)

ammonium test reaction

ammonium + hydroxide → ammonia + water

solubilty of common sodium, potassium and ammonium salts

soluble

solubility of nitrates

soluble

which chlorides are insolube?

silver chloride

lead chloride

which sulfates are insoluble?

lead sulfate

barium sulfate

calcium sulfate

which carbonates are soluble?

sodium carbonate

potassium carbonate

ammonium carbonate

which hydroxides are soluble?

sodium hydroxide

potassium hydroxide

ammonium hydroxide