Oxygen

Question 1

gases present in the air

Answer 1

Nitrogen- 78%
Oxygen- 21%
CO2- 0.04%
Argon- nearly 1%

Question 2

using iron to investigate the proportion of oxygen in the atmosphere

Answer 2

1. Iron reacts with oxygen in the air to remove rustm so iron will remove oxygen from the air
2. to do this experiment, first soak some Iron wool in acetic acid, to catalyse the reaction. Then push the wool into a test tube, put your thumb over the end and insert the tube into a beaker of water
3. overtime the level of water in the test tube will rise
4. mark the starting and finishing position of water
5. fill the tube up to each mark with water and pour the contents into a measuring cylinder to work out the volume at the start and end, use the differencee of volumes to work out the %

Question 3

Using copper to investigate the proportion of oxygen in the atmosphere

Answer 3

1. when it is heatetd, copper reacts with oxygen in the air to make copper (II) oxide and so the reaction uses up oxygen
2. If you heat an excess of copper in a tube and pass air over it using two gas syringes you can use the markers on the syringes to tell how much oxygen has been used up
3. you will measure the change in volume by passing a known volume of air over hot copper and meauring the decrease in volume as the oxygen reacts with it
4. how ever much is lost is then the new percentage

Question 4

making oxygen in the lab

Answer 4

1. use hydrogen peroxide (H202) to decompose into water and oxygen
2. the decompositions rate of reaction can be sped up using a sprinkle of manganese oxide catalyst. The catalyst speed up the reaction without being used up itself
3. Collect the oxygen produced over water (use a delivery tube to bubble the gas into an upsidedown measuring cylinder filled with water

Question 5

eqaution for making oxygen in the lab

Answer 5

2H20 —–.> 2H20 + 02

Question 6

Using phosphorus to investigate the proportion of oxygen in the atmosphere

Answer 6

1. do a similar experiment to the iron one with white phosphorus
2. white phosphorus smoulders in the air to produce phosphorus oxide
3. calculate the amount of oxygen in the air for iron

Question 7

when you burn something it reacts with oxygen in the air (magnesium)

Answer 7

burns with a bright white flame in the air and forms the white powder (magnesium oxide) - slightly alkaline

Question 8

when you burn something it reacts with oxygen in the air (carbon)

Answer 8

needs to be very strongly heated. Has an orangey/yellowy flame, produces co2 gas. (slightly acidic)

Question 9

when you burn something it reacts with oxygen in the air (sulfur)

Answer 9

pale blue flame produces sulfur dioxide (acidic)

Question 10

labotory preparation of co2 using calcium carbonate and dilute hcl

Answer 10

1. calcium carbonate (marble chips) are put at the bottom of the flask and dilute hydrochloric acid is added
2. the dilute hcl reacts with the calcium carbonate to produce calcium chloride, water and carbon dioxide gas
3. the carbon dioxide gas is collected in a gas syringe or using downward delivery

Question 11

thermal decompostition of metal carbonates also produces co2

Answer 11

1. another way of making co2 is by heating a metal carbonate
2. this is an example of thermal decomposition, which is when a substance breaks down into simpler substances when heated.
3. Copper (II) carbonate is a green powder that will easily decompose to form carbon dioxide and copper (II) oxide when you heat it
4. To do the experimment, heat copper (II) carbonate then collect the gas thats given off using the downward delivery method

Question 12

carbon dioxide properties

Answer 12

carbon dioxide is soluble in water

carbon dioxide is denser than air

Question 13

carbon dioxide in carbonating drinks

Answer 13

1. co2 is used in carbonated drinks to make them fizz
2. the co2 is slightly soluble in water and dissolves into the drinks when under pressure. This produces a slightly acidic solution due to the formation of carbonic acid.
3. When you open the bottle the bubbles are the co2 escpaing. If you leave the drink out long enough it will go flat because all of the co2 escapes

Question 14

carbon dioxide in fire estinghisers

Answer 14

1. carbon dioxide is also used in fire extinguishers
2. co2 is more dense than air- so it sinks onto the flames and stops the oxygen the fire needs getting to it
3. carbon dioxide fire extunguhsers are used when water extinguishers aren’t safe, for example putting out electrical fires.