Gas Chemistry

Question 1

The Atmosphere

Answer 1

• 78% nitrogen
• 21% oxygen
• 0.03% carbon dioxide
• 1% argon
• small proportions of miscellaneous noble gases
• varying proportions of water vapour

Question 2

Nitrogen

Answer 2

• Colourless
• Odourless
• Insoluble in water
• Triple covalent bond, hard to break
• Hard to spot
• Diatomic
• Used for liquid coolants and food packaging (inert)

Question 3

Ammonia

Answer 3

• Colourless
• Pungent
• Soluble in water
• Less dense in air
• TEST: Dip a rod in hydrochloric acid and then place rod in the gas. White smoke of aluminium chloride will appear if present
• Used in fertilisers, reacts strongly with acids in soil

Question 4

Hydrogen

Answer 4

• Colourless
• Odourless
• Insoluble in water
• Less dense than air
• Diatomic
• PREPARING AND COLLECTING TEST: Gas jar, trough of water. Magnesium/Zinc reacts vigourously with hydrochloric acid
• TEST FOR PRESENCE: Lit splint, squeaky pop
• Used to solidify fats in magarine, as an alternative to hydrocarbon fuels and in weather balloons

Question 5

Oxygen

Answer 5

• Colourless
• Odourless
• Denser than air
• Diatomic
• TEST FOR PRESENCE: Glowing splint in tube, will relight if present
• TEST FOR PREPARATION: Gas jar, trough of water. Can be made from hydrogen peroxide, which decomposes to form water and oxygen. Manganese(IV) oxide catalyst.
• Oxygen is used in medicine and welding.

Question 6

Metals and Non-Metals

Answer 6

• React with oxygen in the air to produce metal/non-metal oxides.
• Basic oxides react with acids
• Acidic oxides react with alkalis

Question 7

Magnesium

Answer 7

• TYPE: Metal
• REACTION TYPE: Highly exothermic, bright white flame
• OXIDE: White powder, magnesium oxide
• NATURE: Basic

Question 7

Carbon

Answer 7

• TYPE: Non-metal
• REACTION TYPE: Exothermic, glows orange when strongly heated
• OXIDE: Carbon dioxide, colourless and odourless gas
• NATURE: Acidic

Question 8

Sulfur

Answer 8

• TYPE: Non-metal
• REACTION TYPE: Burns slowly, blue flame
• OXIDE: Sulfur dioxide is colourless with a choking smell
• NATURE: Acidic

Question 9

Iron

Answer 9

• TYPE: Metal
• REACTION TYPE: Burns with orange sparks
• OXIDE: Triiron tetroxide, black powder
• NATURE: Basic

Question 10

Copper

Answer 10

• TYPE: Metal
• REACTION TYPE: Burns with orange flame, sometimes blue-green
• OXIDE: Copper oxide, black powder
• NATURE: Basic

Question 11

Carbon Dioxide

Answer 11

• Colourless
• Odourless
• Slightly soluble, forms carbonic acid
• TEST: Gas jar, trough of water. Uses solid calcium carbonate and hydrochloric acid
• Used in fizzy drinks (reversible reaction), fire extinguishers
• REACTION WITH WATER: Forms weak carbonic acid, cannot be isolated from solution
• REACTION WITH LIMEWATER: White precipitate, add more to turn back to colourless