BOTH P1+2 2c gases in the atmosphere

Question 1

what are the four most abundant gases in unpolluted dry air?

Answer 1

nitrogen
oxygen
argon
carbon dioxide

Question 2

what is the percentage of nitrogen in the air?

Answer 2

78.1%

Question 3

what is the percentage of oxygen in the air?

Answer 3

21.0%

Question 4

what is the percentage of argon in the air?

Answer 4

0.9%

Question 5

what is the percentage of carbon dioxide in the air?

Answer 5

0.04%

Question 6

what is the remainder made up of?

Answer 6

other noble gases such as helium

Question 7

how do you measure the percentage of oxygen in the air?

Answer 7

three experiments that are used to measure the percentage of oxygen in the air

• reaction of a substance with oxygen in the air
• the substances are copper, iron and phosphorus

Question 8

what is the experiment to measure the % of oxygen in the air, by reacting it with copper?

Answer 8

two gas syringes on either side od a silica tube packed with copper filings.

• the copper is heated (to create a combustion reaction)
• the gas syringe with 100cm^3 of air in it will move forward as the copper is burned
• this shows the amount of oxygen used in the reaction
• when it has stopped moving the reaction has stopped
• then figure out the percentage change

Question 9

what is the experiment to measure the % of oxygen in the air, by reacting it with iron?

Answer 9

a gas syringe is connected to a conical flask which has wet iron filings in it

• the volume of air decreases as the oxygen is removed as it reacts with iron to form rust
• it may need to be left for a week, so the reaction can be completed

Question 10

what is the experiment to measure the % of oxygen in the air, by reacting it with phosphorus?

Answer 10

a trough is half filled with water, then an evaporating basin with phosphorus is placed on the water, over the basin a bell jar is placed.

• light phosphorus on fire and it will react with oxygen, the water level in the bell jar rises
• by determining how much the water has risen by it will show the oxygen in the air
• this is a displacement of water

Question 11

what happens in the combustion of magnesium?

Answer 11

the silver ribbon of metal burns in oxygen to form magnesium oxide

• it will burn with a bright white flame
• it will turn into a bight white flame

Question 12

what is the symbol equation for the combustion of magnesium?

Answer 12

2Mg(s) + O2(g) -> 2MgO(s)

Question 13

what happens when MgO reacts with water?

Answer 13

it forms magnesium hydroxide

which is an alkaline

Question 14

what happens in the combustion of sulphur?

Answer 14

the yellow powder burns in oxygen a colourless gas with a blue flame to form sulphur dioxide

Question 15

what is the symbol equation for the combustion of sulphur?

Answer 15

S(s) + O2(g) -> SO2(g)

Question 16

what happens when SO2 reacts with water?

Answer 16

it forms an acidic solution, of sulphurous acid

Question 17

what happens in the combustion of hydrogen?

Answer 17

hydrogen burns in oxygen with a pale blue flame to form water

Question 18

what is the symbol equation for the combustion of hydrogen?

Answer 18

2H2(g) + O2(g) -> 2H2O(l)

Question 19

what is thermal decomposition?

Answer 19

reactions where a substance breaks down due to the action of heat

Question 20

what is the reaction for decomposition of the lower half of the reactivity series?

Answer 20

metal carbonate -> metal oxide + carbon dioxide

Question 21

describe the thermal decomposition of copper (II) carbonate.

Answer 21

copper(II) carbonate is a green powder and slowly darkens as black copper(II) oxide is produced
- there is carbon dioxide given off

Question 22

what is the equation for the thermal decomposition of copper(II) carbonate?

Answer 22

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

copper (II) carbonate -> copper (II) oxide + carbon dioxide

Question 23

how does the production of cement effect the atmospheric CO2 levels?

Answer 23

in the production of cement there is a release of carbon dioxide from the calcium carbonate, which adds CO2 and therefore contributes to the enhanced greenhouse effect

Question 24

what are the sources of carbon dioxide, in the atmosphere?

Answer 24

• combustion of wood and fossil fuels
• respiration of plants and animals
• thermal decomposition of carbonate rocks
• the effect of acids on carbonates

Question 25

what is the greenhouse effect?

Answer 25

• a shortwave radiation from the sun strikes the earths surface
• then it gets absorbed and re-emitted as infrared radiation
• lots of it is trapped inside by greenhouse gases

Question 26

purpose of greenhouse gases in the atmosphere?

Answer 26

absorb and store the heat energy

Question 27

what are the greenhouse gases?

Answer 27

carbon dioxide, methane and water vapour

Question 28

what is the enhanced greenhouse effect?

Answer 28

when there is a significant amount of greenhouse gases that surpass the earths natural conditions

• the extra gases trap extra heat energy
• makes the earth hotter