Air

Question 1

Percentages of air

Answer 1

Nitrogen 78.1%
Oxygen 21.0%
Argon 0.9%
Carbon Dioxide 0.04%

Question 2

Experimenting percentage of Oxygen in air

Answer 2

-Two syringes with a silica tube with copper in, with 100cm^3 of air in the whole system
-Heat the tube as the air is pushed forwards and backwards and the copper turns black to COPPER (ll) OXIDE
-The volumes of gas in the syringe falls as the oxygen is used up.
2Cu(s) + O2(g) –> 2CuO(s)

Question 3

Collecting and testing for gases: Hydrogen

Answer 3

-Less dense than air, collect upwards or over water
-Squeaky pop test- popping noise when a lit splint is held to mouth of the test tube
2H2(g) + O2(g) –> 2H2O(l)

Question 4

Collecting and testing for gases: Oxygen

Answer 4

• Similar density to air, collect over water

- Relights a glowing splint

Question 5

Collecting and testing for gases: Carbon Dioxide

Answer 5

-Denser than air, collect downwards or over water
-Turns lime water milky when bubbled through, forming Calcium Carbonate
Ca(OH)2(aq) + CO2(g) –> CaCO3(s) + H2O(l)

Question 6

Collecting and testing for gases: Ammonia

Answer 6

• Less dense than air, collect upwards and NOT over water

- Turns damp red litmus paper blue because its an alkali

Question 7

Collecting and testing for gases: Chlorine

Answer 7

• Denser than air, collect downwards and NOT over water

- Green gas that bleaches damp litmus paper

Question 8

Carbon Dioxide

Answer 8

• Colourless, odourless gas
• Denser than air
• Slightly soluble in water

It also absorbs infra-red radiation and then the energy is transferred by collisions to other molecules, warming the whole atmosphere

Question 9

Using Carbon Dioxide in fizzy drinks

Answer 9

Carbon Dioxide is used in carbonating drinks because it dissolves in water under pressure. When you open the bottle, the pressure falls and gas bubbles out of the solution

Question 10

Using Carbon Dioxide in fire extinguishers

Answer 10

Using water could cause problems around electricity. Dense gas sinks onto the flames and prevents more oxygen from reaching them.

Question 11

Making Carbon Dioxide

Answer 11

There is a reaction between dilute hydrochloric acid and calcium carbonate (marble chips). There is a thistle funnel, and the side arm boiling tube leads up under water to collect carbon dioxide upwards.

CaCO3(s) + 2HCl(aq) –> CaCl2(aq) + CO2(g) + H2O(l)

Question 12

Burning Sulfur

Answer 12

Tiny, almost invisible blue flame which is stronger in pure oxygen.
Poisonous, colourless SULFUR DIOXIDE gas is produced.
S(s) + O2(g) –> SO2(g)

Question 13

Burning Carbon

Answer 13

If heated STRONGLY
Produces colourless CARBON DIOXIDE gas
Depending on the purity of carbon, there can be a small yellow-orange flame and perhaps some sparks.
C(s) +O2(g) –> CO2(g)