Inorganic Chemistry - Gases in the Atmosphere

Question 1

what is the percentage by volume of nitrogen in the air?

Answer 1

78.1

Question 2

what is the percentage by volume of oxygen in the air?

Answer 2

21.0

Question 3

what is the percentage by volume of argon in the air?

Answer 3

0.9

Question 4

what is the percentage by volume of carbon dioxide in the air?

Answer 4

0.04

Question 5

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

Answer 5

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

Question 6

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

Answer 6

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 7

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

Answer 7

start volume - final volume / start volume x 100

Question 8

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

Answer 8

1. place phosphorus 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.

Question 9

what happens during the combustion of magnesium in oxygen?

Answer 9

magnesium reacts with oxygen producing a bright white flame and leaving behind a white ash of magnesium oxide
2Mg (s) + O₂ (g) → 2MgO

Question 10

what happens during the combustion of hydrogen in oxygen?

Answer 10

hydrogen reacts with oxygen in an explosive reaction. this is the basis of the ‘squeaky pop’ test for hydrogen in a test tube
2H₂ (g) + O₂ (g) → 2H₂O (l)

Question 11

what happens during the combustion of sulfur in oxygen?

Answer 11

sulfur reacts with oxygen producing a blue flame
S (s) + O₂ (g) → SO₂ (g)

Question 12

what is thermal decomposition?

Answer 12

the process of breaking down by heating

Question 13

what happens when metal carbonates are heated?

Answer 13

they thermal decompose into metal oxides and carbon dioxide. e.g:
CuCO₃ -> CuO + CO₂

Question 14

what type of gas is carbon dioxide?

Answer 14

a greenhouse gas

Question 15

what is the result of carbon dioxide concentration increasing?

Answer 15

carbon dioxide absorbs infra-red radiation and therefore warms the atmosphere, leading to global warming