Inorganic Year 1

Group 2 elements solubility down the group

Hydroxide - more soluble

Sulfate - less soluble

How to test for sulfate ions

Add acidified barium chloride (BaCl2) acidified with HCl

White precipitate will form

HCl removes any sulfates or carbonates

How are group 2 compounds used?

Calcium hydroxide - agriculture to neutralise soils

Magnesium hydroxide - neutralise excess stomach acid

Ionic equation: H+ (aq) + OH- (aq) → H2O (l)

Barium sulfate is used in barium meals for x-rays

Magnesium being used for the extraction of titanium

Mg acts as a reducing agent

1. TiO2 is converted to TiCl4 at 900 celsius

2. TiCl4 is purified by fractional distillation in an argon atmosphere

3. Ti is extracted in an Argon atmosphere at 500 celsius

TiO2 + 2Cl2 + 2C → TiCl4 + 2CO

TiCl4 + 2Mg → Ti + 2MgCl2

Why is TiO2 converted to TiCl4?

Can be purified via fractional distillation → TiCl4 is molecular NOT IONIC LIKE TIO2 at room temperature

Why is titanium expensive?

1. Mg is expensive

2. Batch process → slower and requires more labour

3. Argon is expensive and it’s required to remove moisture as TiCl4 can hydrolyse

4. high temperature

Calcium oxide and calcium carbonate to remove sulfur dioxide

1. Burning fossil fuels produces SO2 which pollutes the atmosphere

2. SO2 can be removed by flue gases → wet scrubbing

CaO + 2H2O + SO2 → CaSO3 + 2H2O

CaCO3 + 2H2O + SO2 → CaSO3 + 2H2O + CO2

What colour is fluorine?

Yellow

What colour is chlorine?

Green

What colour is bromine?

Brown

What colour is iodine?

Grey

What happens oxidising strength down group 7?

Decreases

When will a halogen displace a halide?

When it’s below it in the period table

The table

table

How to make bleach

2NaOH + Cl2 → NaClO + NaCl + H2O

What are the disadvantages and advantages of using chlorine to sterilise water?

• Kills disease-causing microorganism

• Prevents growth of algae → no smell or bad taste and removes discolouration

• Can irritate the respiratory system if breathed in

What happens to the reducing power down the group of ions?

increases

1. ions get bigger → electrons are further away

2. Greater shielding effect due to extra electron

Reaction of NaF and NaCl with sulfuric acid

NaX + H2SO4 → HX + NaHSO4

Misty white fumes of HX

HF and HCl aren’t strong enough reducing agents so reaction stops

Reaction of NaBr with sulfuric acid

NaBr + H2SO4 → NaHSO4 + HBr

2HBr + H2SO4 → Br2 + SO2 + 2H2O

White steamy fumes of HBr, acidic gas of SO2, orange fumes of Br2

Reaction of NaI with sulfuric acid

NaI + H2SO4 → NaHSO4 + HI

2HI + H2SO4 → I2 + SO2 + 2H2O

6HI + SO2 → H2S + 3I2 + 2H2O

H2S has a smell of bad eggs, acidic gas of SO2, yellow solid of sulfur, Black solid and purple fumes of iodine, HI has white steamy fumes

Silver nitrate to test for halides

1. Add dilute nitric acid to remove ions that may interfere with the test

2. Add a few drops of silver nitrate

Ag+ + X- → AgX

colour of precipitate to identify halide with silver nitrate and rate of formation

• F- has no precipitate

• Cl- has a white precipitate

• Br- has a cream precipitate

• I- has yellow precipitate

AgCl forms the slowest and AgI forms the fastest

How to test which precipitate of halide ions is which

Add ammonia

Cl- dissolves in dilute ammonia

Br- dissolves in concentrated ammonia

I- does not dissolve

What are the two ways of identifying Group 2 ions?

Flame test and NaOH

Flame test to identify group 2 ions

1. Dip a nichrome wire loop in concentrated HCl

2. Then dip nichrome wire loop into an unknown compound

3. Hold the loop in blue part of bunsen burner flame

4. Observe colour change

What are the colours for group 2 metal ions and flame test?

Calcium ions = brick red

Strontium ions = red

Barium ions = pale green

How to use NaOH to identify Group 2 metal ions

1. Use dilute sodium hydroxide solution

2. Add NaOH drop wise and observe precipitate

3. Keep adding until NaOH is in excess

What are the results for NaOH with group 2 metal ions from normal to excess?

Magnesium = slight white precipitate → white precipitate

Calcium = Slight white precipitate → slight white precipitate

Strontium = slight white precipitate → slight white precipitate

Barium = no change → no change

How to test for ammonium ions?

1. Ammonia gas is alkaline → red litmus paper will turn blue

2. Add NaOH to ammonium ions and heat to form ammonia gas

How to test for sulfate ions?

Add barium chloride acidified with HCl → white precipitate forms

How to detect carbonates

1. Add dilute HCl → fizz

2. Bubble through limewater → goes cloudy