Gases in the atmospheres

Question 1

whats the main gases in the atmosphere

Answer 1

78% nitrogen
21% oxygen
0.05% co2

Question 2

how can the percentage of air be found bhy

Answer 2

reacting a non metal and a metal together in a fixed volume of air

Question 3

explain an experiment to find the percentage of oxygen

Answer 3

• burn a small amount of phosphorus in a bell jar that is sitting in a trough of water
• as phosphorus burns it uses up oxygen inside the bell jar and water rises
• measure the water levels before and after the experiment

Question 4

why is phosphorus a good/bad metal to use in the experiment to determine percentage of air

Answer 4

-it burns readily until all oxygen is used up
- it is toxic and hazardous

Question 5

explain an experiment to determine the percentage of oxygen in air

Answer 5

to measure the volume between the final mark on the scale and the tap

Fill the burette with water up to lowest mark, 50.0 mL, and then let it drain into a small measuring cylinder

Measure the volume of water
Add a little water to moisten the inside of the burette

Make sure the tap is closed and sprinkle some iron filings or push a piece of iron wool into the bottom of the burette

Invert the burette into a trough of water and clamp the burette vertically

Note and record the position of the water level

After 3-4 days note the new position of the water level

Question 6

what is the meaning of combustion

Answer 6

the burning of a substance in the presence of oxygen

Question 7

what do combustion reactions produce

Answer 7

oxides

Question 8

what type of reaction is combustion

Answer 8

exothermic

Question 9

Magnesium combustion reaction observations

Answer 9

• intense white flame produced
• white powder produced

Question 10

hydrogen combustion reaction observation

Answer 10

-exothermic
-water is produced

Question 11

sulfur combustion reaction observation

Answer 11

• blue flame
• colorless, poisonous gas produced

Question 12

2Mg (s) + O2 (g) –> ?

Answer 12

2Mgo (s)

Question 13

definition of thermal decomposition

Answer 13

where a substance breaks down due to the action of heat

Question 14

decomposition of metal carbonates

Answer 14

metal carbonate -> metal oxide + carbon dioxide

Question 15

thermal decomposition of copper (II) carbonate

Answer 15

green powder slowly darkens to a black powder

Question 16

equation for thermal decomposition of copper (II) carbonate

Answer 16

CuCO3 (s) -> CuO (s) + CO2 (g)

Question 17

explain the greenhouse effect

Answer 17

• when shortwave radiation from the sun strikes the earths surface it is reabsorbed and re-emitted from the surface as infrared radation
• most heat is trapped inside the atmosphere by GHGs which is stored as energy
• increasing levels of carbon dioxide is trapping extra heat energy