Chemistry Topic 4 Gases

What is the percentage concentration of gases in the atomosphere?

Nitrogen- 78%

Oxygen- 21%

Argon- <1%

Carbon dioxide- 0.03-0.04%

What are the physical properties of nitrogen?

Colourless and odourless gas

Insoluble in water

Neutral gas

What is the reactivity of nitrogen?

It is unreactive as it has a strong triple covalent bond and takes a lot of energy to break

What are the uses of nitrogen?

Liquid nitrogen

Inserted in food packaging for freshness

Manufacturing of ammonia

What are the physical properties of ammonia (NH2)?

Colourless, pungent gas

Soluble in water

Less dense than air

What is the test for ammonia?

Dip glass rod in concentrated HCl and place in sample of gas

White smoke will be observed if ammonia is present

What are the uses of ammonia?

Manufacturing of fertilisers

What are the physical properties of hydrogen?

Colourless and odourless gas

Less dense than air

Insoluble in water

Neutral

What is the test for hydrogen?

Apply a lighted splint

If a squeaky pop is heard then hydrogen is present

What are the uses of hydrogen?

Fills meteorological balloons

Hardens oils to butter or margarine

Has potential as a clean

What is the test for oxygen?

Apply a glowing splint

Oxygen relights a glowing splint

What are the uses of oxygen?

Breathing apparatus

Welding

How can you test to see if you had acidic/basic oxides?

Universal indicator

What are the physical properties of carbon dioxide?

Colourless, odourless gas

Slightly soluble in water

Acidic

Less dense than air

What are the uses of carbon dioxide?

Fire extinguishers

Fizzy drinks

Dry ice

What is the preparation of carbon dioxide?

Calcium carbonate and dilute hydrochloric acid react to form carbon dioxide

CaCO3 + 2HCl → CaCl2 + CO2 + H2O

What is the test for carbon dioxide?

Bubble the gas through colourless limewater

Carbon dioxide turns limewater milky

What is the reaction of carbon dioxide and water?

Carbon dioxide forms carbonic acid

CO2 + H2O → H2CO3

This acid can’t be isolated from its solution. It causes acidity in fizzy drinks