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Chemistry 6 - Organic Chemistry > Alkanes as Fuels > Flashcards

Flashcards in Alkanes as Fuels Deck (36)
1

what is the equation for complete combustion

hydrocarbon + oxygen = carbon dioxide + water

2

what would the complete combustion of propane look like

- propane has a molecular formula of C3H8
- so the combustion equation is C3H8 + ?02 = ?CO2 + ?H20
- there are three carbons on the left so there are 3 CO2 molecules
- there are 8 hydrogens so there are 4 H20 molecules
- on the right that makes a total of 10 oxygen atoms
- so on the left there must be 5 02 molecules
- giving: C3H8 + 5O2 = 3CO2 + 4H20

3

what is the first problem or disadvantage that comes to mind when completely combusting a hydrocarbon

- CO2 is produced as a byproduct
- which contributes to the greenhouse effect
- which accelerates global warming and climate change

4

what is incomplete combustion

when all of the hydrocarbon doesnt completely burn with oxygen

5

why would incomplete combustion take place

- if there was an insufficient supply of oxygen present during the burning
- or the reaction was too rapid

6

what happens to the hydrogen atoms during incomplete combustion and is the product harmful

- they burn with oxygen and just form water
- this is a harmless product

7

what happens to the carbon atoms during incomplete combustion

- some of the carbon atoms form gaseous carbon monoxide
- or solid carbon
- these are harmful products and can cause issues

8

why can you know when solid carbon has been formed in incomplete combustion just from looking

- as the solid carbon can be seen as smoke in the air
- or soot on the burner

9

what would be the equation for the incomplete combustion of propane that forms two moles of CO2 as one of the products, with solid carbon being the polluting byproduct

- C3H8 + ?O2 = 2CO2 + ?C + ?H20
- you have 8 hydrogens on the left so 4 H20 on the right
- you then have a total of 8 oxygens on the right so you have 4 O2 on the left
- and you have 2 carbons on the right when there are 3 on the left so you only have one carbon atom forming the solid
- C3H8 + 4O2 = 2CO2 + C + 4H20

10

how would you explain the combustion of the propane that took place in the previous equation

- 2 out of 3 of propane's carbon atoms completely combusted
- while the last one doesnt

11

what does the solid carbon actually look like

- tiny particles in the atmosphere
- which can be breathed in or influence climate change

12

what does carbon monoxide do when breathed in

- it prevents the transport of oxygen around the body
- as it binds to haemoglobin in the red blood cells more strongly than oxygen does

13

why is carbon monoxide such a dangerous gas

- it is colourless and odourless
- so people breathe it in without knowing
- hence why its called the silent killer

14

what would the equation be for the incomplete combustion of propane if one mole of CO2 was produced on the right side, with carbon monoxide being one of the byproducts

- C3H8 + ?O2 = CO2 + ?CO + ?H20
- 8 hydrogens so 4 H20s
- 3 carbons on the left so you have 2 COs
- meaning you have a total of 8 oxygens on the right
- so you have 4 O2s
- C3H8 + 4O2 = CO2 + 2CO + 4H20

15

what are unburned hydrocarbons

- hydrocarbons that dont burn at all during combustion
- abbreviated to HC

16

what happens to unburnt hydrocarbons since they dont burn

they are released into the atmosphere unchanged

17

why should atoms of sulfur in molecules in crude oil not theoretically be there when burning a hydrocarbon

- because they can be removed by fractional distillation, cracking and reforming
- but neither of these are perfect

18

what products are formed when a hydrocarbon with sulfur impurities is burned and then released into the atmosphere

- when burned sulfur dioxide is formed and released
- when in the atmosphere it can react with it to form sulfur trioxide

19

what are the equations for the production of sulfur dioxide and trioxide

- S + O2 = SO2
- 2SO2 + O2 = 2SO3

20

what kind of gases are sulfur dioxide and trioxide and what do they from when dissolved in water

- they are both acidic oxides
- when dissolved in water sulfur dioxide forms sulfurous acid
- and sulfur trioxide forms sulfuric acid

21

what is the equation for the production of sulfurous acid and sulfuric acid

- SO2 + H20 = H2SO3 (sulfurous acid)
- SO3 + H20 = H2SO4 (sulfuric acid)

22

what do both of these form in the atmosphere and what are its impacts

- they form acid rain
- which causes environmental damage
- to things like aquatic life and crops

23

how are oxides of nitrogen formed

- under very high temperatures like in car engines
- nitrogen molecules can burn with oxygen molecules in the air
- to form various oxides of nitrogen

24

what is the formula for an oxide of nitrogen and what are the most common ones

- NOx
- the common ones are nitrogen monoxide (NO)
- and nitrogen dioxide (NO2)

25

at very high temperatures what is the main reaction between nitrogen and oxygen molecules (its equation)

N2 + O2 = 2NO

26

since nitrogen dioxide is soluble in water, what two products does it form when reacting with water in the atmosphere what is the equation for this

- 2NO2 + H2O = HNO2 + HNO3
- nitrous and nitric acid

27

are nitrous and nitric acid any different to sulfurous and sulfuric acid

- no
- they also make acidic rain which damages the environment

28

what are catalytic converters

- pieces of machinery in vehicles
- built to reduce the amount of pollutants released
- by converting them into less polluting products

29

what is the common build of a catalytic converter

- they contain platinum, rhodium and palladium in small quantities
- these are spread over a honeycomb mesh to increase the surface area

30

what is a three-way catalyst

- a catalytic converter that can remove three different types of pollutants
- carbon monoxide
- oxides of nitrogen
- and unburned hydrocarbons

31

how is carbon monoxide and unburned hydrocarbons converted to cleaner products

by oxidising them

32

what would the oxidisation of carbon monoxide look like

2CO + O2 = 2CO2

33

what would the oxidisation of an unburned hydrocarbon look like (C8H18)

C8H18 + 12.5O2 = 8CO2 + 9H20

34

how are oxides of nitrogen converted and what is especially good about this reaction

- 2NO + 2CO = N2 + 2CO2
- its effective because it uses two polluting products to convert each other into cleaner ones

35

can catalytic converters work on sulfur and what is the best way to prevent sulfur based polllution

- they dont really work
- so the best way to prevent pollution is to remove the sulfur compounds from the fuel
- before the fuel is burned

36

what is fuel that has has its sulfur impurities removed called

- low sulfur fuel
- or ultra low sulfur fuel