Topic 4 - Gases in the Atmosphere

Question 1

what gases are in the atmosphere?

Answer 1

78% nitrogen, 21% oxygen, almost 1% argon and 0.04% carbon dioxide

Question 2

why is iron used to determine the percentage of oxygen in the air?

Answer 2

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

Question 3

how would you use iron to investigate the percentage of oxygen in air?

Answer 3

1. soak iron wool in acetic acid (catalyst). push the wool into a measuring cylinder and invert the cylinder into a beaker of water.
2. record the starting position of water
3. overtime, the level of water will rise because the iron reacts with the oxygen in the air and the water rises to fill the space
4. leave until the level stops rising and record the finishing position

Question 4

what formula would you use to calculate the percentage of oxygen in the air from the iron wool practical?

Answer 4

start volume - final volume / start volume x 100

Question 5

how do you use phosphorus to determine the percentage of oxygen in the air?

Answer 5

1. place pgosphorus in a tube and attach a glass syringe at either end
2. heal the phosphorus and use the syringes to pass the air over it. the phosphorus will react to make phosphorus oxide
3. as it reacts, the amount of air in the syringes will decrease
4. measure the starting and final volume of air using the scale on the syringe.