Group 7 The Halogens Flashcards by Kat Smith

Colour of fluorine + state

Pale yellow
Gas

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Chlorine colour + state

Pale green gas

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Bromine colour and state

Brown -orange
Liquid

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Iodine colour and state

Grey
Solid

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Trend in boilings points group 7

Increase down the group
Increase Van Der waals due to increasing size and relative mass of atoms

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Trend in electronegativity group 7

This decreases going down the group
As the atoms get larger the distance between positive nucleus and bonding electron increases + more shielding

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Displacement rule in halogens

A more reactive halogen will displace a less reactive halogen

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What colour is iodine solution

Brown

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Standard equation of halogens displacing each other half/ ionic equation

X2 + 2Y- —> 2X- + Y2

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How is bleach made which reaction

Disproportionating reaction

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Equation for making bleach

2NaOH + Cl2 —> NaClO + NaCl + H2O

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Uses of bleach

Cleaning agents
Treating water
Bleaching fabrics

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What happens in a disproportionation reaction w chlorine

The chlorine is reduced and oxidised simultaneously

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Why is chlorine added to water

To kill bacteria

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Reaction when water is added to chlorine

H2O + Cl2 —> 2H+ + Cl- + ClO-

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Reaction when chlorine is added to water but in sunlight ionic

2H2O + Cl2 —> 4H+ + 2Cl- + O2

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Advantages of chlorinating drinking water x4

Destroys microorganisms that causes diseases
Long lasting so reduces bacteria build up
Reduces the growth of algae
Not doing it can lead to cholera epidemic

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Disadvantages of chlorinating drinking water x3

Chlorine gas is toxic
Liquid chlorine causes chemical burns
Chlorine could react with organic compounds to make chloroalkanes. These can cause cancer.

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Are halides oxidising or reducing agents

Reducing agents

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Trend in reducing ability of halides review

Increase going down
They are reducing agents so oxides themselves so they lose electrons
Going down distance between outer electron and nucleus increases and more shielding so attraction is weaker.

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Test for halide ions

1) add dilute nitric acid to remove the any ions that could give false results
2) add silver nitrate
3) further test with ammonia

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Chloride ions form what colour precipitate

White

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Bromine produce what coloured ions..

Cream

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Iodine produce what coloured ions

Yellow

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Half equation standard for halide test with silver nitrate

Ag+(aq) + X-(aq) —> AgX(s)

Cl- white precipitate with ammonia observation

Dissolves in dilute ammonia

I- yellow precipitate with ammonia observation

Insoluble in concentrated ammonia

Br- cream precipitate with ammonia observation

Insoluble in concentrated ammonia

How to test for group 2 ions

Flame test Dip wire in hydrochloric acid Place loop into blue flame

What colour calcium on flame test

Dark red

What colour strontium in flame test

Red

What colour barium in flame test

Green

How to test for ammonium compounds

Add sodium hydroxide Heat gently Positive - ammonia gas produced bleaches litmus paper blue

Test for hydroxide + problem

They are alkaline so will turn red litmus paper blue However lots of thing turn litmus paper blue so need to do further tests

Test for carbonates

Add acid E.g. hydrochloric acid Fizzing and Produces CO2 gas ( if positive) Limewater turns cloudy if CO2 is present

What order to test ions + why

1) carbonates 2) sulfates 3) halides To prevent false positives

Ionic equation for carbonate test

CO3 -2 + 2H+ —> CO2 + H2O

Nitrogen gas formula

Forulma bleach

NAClO

Half equation to show oxidation of halide ion to halogen

2X- —> X2 +2e-

How to test for barium

Add any sulphate E.g. SO42- White precipitate

Bromine is what colour solution

Yellow

Reaction when chlorine is added to water not ionic

2Cl2 + 2H2O —> 4HCl +O2

Ionic equation test for barium with…

Sulfates Ba2+ + SO4-2 —> BaSO4

Equation when chlorine is added to drinking water

2Cl2 + 2H2O —> 4HCl +O2

Why is catalyst used in equilibrium

No effect on yield Lowers temperature used Lowers cost

State why not more than the minimum ionisation energy is used to ionise a sample

To prevent further ionisation

Explain why sodium oxide forms alkali solution when reacts with water

Contains O2- ions React with water to form OH- ions O2- + H2O —> 2OH-

Metal oxide + hydroxide

Metal oxide ion + water

Why is second ionisation energy higher than first ionisation energy

More energy to remove an electron from a more positive ion

Which element in period 2 has the highest 2nd ionisation energy

Chlorine + aqueous sodium hydroxide cold dilute

2NaOH + Cl2 —> NaCl + NaOCl + H2O

Ionic equation w state symbols of metal reacting with water group 2

X (s) + 2H2O(l) —> X+2(aq) + 2OH- (aq) +H2(g)

Practical steps to determine solubility of solution

Take a known volume of saturated solution Evaporate to filtrate dryness Weigh the residue

Equation metal hydroxide + sulfuric acid

X(OH)2 + H2SO4 —> XSO4 + 2H2O

Reactivity with water down group 2

Increases

Why should you not add water to burning magnesium

Forms hydrogen Which is flammable

Strontium chloride + sodium sulfate

Sodium chloride + strontium sulfate

How to test for presence of bromide ions w ammonia

Add nitric acid then silver nitrate Then add dilute ammonia Cream precipitation forms No visible change

Why does calcium have higher melting point than strontium

Delocalised electrons are closer to positive nucleus because atomic radius is smaller This means stronger metallic bonding

Equation chlorine redissolving in ammonia

AgCl(s) + 2NH3 (aq) —> Ag(NH3)2 + (aq) + Cl-

Why is chlorine added to water even though it is toxic

Not harmful in low concentration

Sulfur if acid formula

H2SO4

Which halide ion with sulphuric acid is not a redox equasion

Chlorine + fluorine

In the tests for halides why is excess silver nitrate used

To ensure ALL the halide ions precipitate out

Reaction sodium halide and sulfuric acid + what do you see

H2SO4 + NaX —> NaHSO4 + HX Misty fumes

Reaction concentrated sulphuric acid with fluorine and chlorine + why

No reaction Sulfuric acid is not a strong enough oxidising agent to oxides chloride or fluoride ions.

Bromide and concentrated sulfuric acid + which oxidised and reduced + what observation

2Br- —> Br2 + 2e- (oxidised) H2SO4 + 2H+ + 2e- —> SO2 + 2H2O (reduced) Combine for overall equations Orange vapour

Iodine ions with concentrated sulfuric acid

1) NaI + H2SO4 —> NaHSO4 + HI 2) 2H+ + 2I - + H2SO4 —> I2 + SO2 + 2H2O 3) 6HI + SO2 —> H2S + 3I2 + 2H2O

Role of chloride ions in NaCl + H2SO4 —> NaHSO4 + HCl

Base

Bromine colour in solution

Orange

Iodine colour in solution

Brown

As you move from HCl to HI The bond dissociation energy… The bond polarity …..

Decreases Decreases

As you move from HCl to HI they are more/less easily oxidised in aqueous solutions

Role of chlorine in NaCl + H2SO4 —> NaHSO4 + HCl

Proton donor

Colour magnesium hydroxide

White

What colour are the hydroxides of group 2

WHITE ALL