Gases in the Atmosphere

Question 1

what is the percentage of nitrogen in the atmosphere?

Answer 1

78%

Question 2

what is the percentage of oxygen in the atmosphere?

Answer 2

21%

Question 3

what is the percentage of argon in the atmosphere?

Answer 3

nearly 1%

Question 4

what is the percentage of carbon dioxide in the atmosphere?

Answer 4

0.04%

Question 5

how to measure the proportion of oxygen in the atmosphere using iron

Answer 5

iron reacts with oxygen in the air to form rust - so iron will remove oxygen from the air:

1. soak some iron wool in acetic acid (the acid will catalyse) - then push the wool into a measuring cylinder and invert the measuring cylinder into a beaker of water
2. record the starting position of the water using the scale on the measuring cylinder - this is the starting volume of air
3. the level of the water in the measuring cylinder will rise
4. this is because the iron reacts with the oxygen in the air to make iron oxide - the water rises to fill the space the oxygen took up
5. leave the measuring cylinder for around a week or until the water level stops changing
6. record the finishing position of the water - this is the final volume of air

Question 6

how to calculate the percentage of oxygen

Answer 6

start volume - final volume/start volume x 100

NOTE: the answer you get should be about 20%

Question 7

how to use phosphorus to determine the percentage of oxygen in the air

Answer 7

1. place the phosphorus in a tube and attach a glass syringe at either end - make sure one of the syringes is filled with air and the other is empty
2. heat the phosphorus and use the syringes to pass the air over it - the phosphorus will react with oxygen in the air to make phosphorus oxide
3. as it reacts, the amount of air in the syringes will decrease
4. measure the starting and final volumes of air using the scale on one of the syringes
5. calculate the percentage of oxygen using the formula