combustion

Question 1

describe combustion

Answer 1

combustion reacts give out heat and have large negative enthalpies

Question 2

what happens when there is more carbon present during a combustion reaction

Answer 2

the more carbons present, the greater the heat output

Question 3

define a fuel

Answer 3

substances that release heat energy when they undergo combustion

they also store a large amount of energy for a small amount of weight

Question 4

define incomplete combustion

Answer 4

when fuels are burnt in a limited supply of oxygen, the poisonous gas carbon monoxide, CO is formed

Question 5

when is incomplete combustion most common

Answer 5

incomplete combustion often happens with long chain hydrocarbons which need more oxygen to burn compared with shorter chains

Question 6

state all pollution products that may occur when hydrogen-carbon based fuels burn

Answer 6

carbon monoxide
nitrogen oxides
sulfur dioxide
particulates
sulfur dioxide
unburnt hydrocarbons
carbon dioxide
water vapour

Question 7

how is carbon monoxide made

Answer 7

by incomplete combustion

Question 8

how are nitrogen oxides produced

Answer 8

when there is enough energy for nitrogen and oxygen in the air to combine

For example, this happens in a petrol engine at high temperatures present. these oxides may react with water vapor and oxygen in the air to form nitric acid. they are therefore contributors to acid rain and photochemical smog

Question 9

what are the three type of nitrogen oxide

Answer 9

NO
NO2
N2O4

THEY ARE OFTEN ABBREVIATED TO NOX

Question 10

How is sulfur dioxide made

Answer 10

it is produced from sulfur-containing impurities present in crude oil. this oxide combines with water vapour and oxygen in the air to form sulfuric acid

sulfur dioxide is a contributor to acid rain

Question 11

what can carbon particulates do

Answer 11

exacerbate asthma and cause cancer

Question 12

what do unburnt hydrocarbons do

Answer 12

unburnt hydrocarbons may enter the atmosphere and these are significant greenhouse gases

they contribute to photochemical smog which can cause a variety of health problems

Question 13

what does sulfur dioxide do

Answer 13

a gas that causes acid rain by combining oxygen and water in the atmosphere to form sulfuric acid

Question 14

what are the gases given out by power stations called

Answer 14

flue gases

Question 15

what is the process of removing sulfur dioxide called

Answer 15

flue gas desulfirisation

Question 16

explain the method of flue gas desulfirisation

Answer 16

a slurry of calcium oxide and water is sprayed into the flue gas which reacts with the calcium oxide and water to form calcium sulfite, which can be further oxidized to calcium sulfate this is also called gypsum

Question 17

define gypsum

Answer 17

gypsum is a saleable product as it is used to make builders’ plaster and plasterboard

Question 18

what happens in the alternative process of flue gas desulfirisation

Answer 18

an alternative process uses calcuim carbonate rather than calcuim oxide

Question 19

what produces the most of the pollutatnts

Answer 19

the internal combustion engine produces most of the pollutants, though sulfur is now removed from petrol so that sulfur dioxide has become less of a problem

Question 20

what do all new cars have

Answer 20

all new cars with petrol engines are now equipped with catalytic converters in their exhaust systems.

these reduce the output of carbon monoxide, nitrogen oxides, and unburnt hydrocarbons in the exhaust gas mixture

Question 21

what is the catalytic convertor made of

Answer 21

the catalytic convertor is a honeycomb made of ceramic material coated with platinum and rhodium metals

these are the catalysts.

Question 22

what does the honeycomb shape provide for the catalytic convertor

Answer 22

an enormous surface area, so a little of expensive metals goes a long way

Question 23

what happens with the polluting gases in the catalytic convertor

Answer 23

as the polluting gases pass over the catalyst, they react with each other to form less harmful products

the reactions take place on the surface of the catalyst, on the layer of platinum and rhodium metals

Question 24

explain why greenhouse gases become very warm inside

Answer 24

green house gases become very warm inside.

visible rays from the sun pass through the glass

rather than escaping their energy is absorbed by everything inside the greenhouse and re-radiated as infrared energy, which is heat

infrared energy has a longer wavelength and cannot pass back out through the glass

Question 25

why is carbon dioxide important

Answer 25

it traps infrared radiation so that the Earth’s atmosphere heats up

this is important for life because, without carbon dioxide and other greenhouse gases, the earth would be too cold to sustain life

Question 26

why does the concentration of water vapour stay roughly the same

Answer 26

because of the equilibrium that exists between the water vapour and liquid water

Question 27

what would happen if the temperature of the atmosphere rises

Answer 27

there will be more water vapour in the air and therefore more greenhouse warming.

this may be offset by greater cloud formation and clouds reflect solar radiation

Question 28

define carbon-nuetral

Answer 28

activities that produce no cabron dioxide emissions overall are referred to as carbon neutral