Alkanes

Question 1

What is a combustion reaction?

Answer 1

When something burns in oxygen, to produce heat energy.

It is exothermic

Question 2

what is complete combustion?

Answer 2

when a substance completely burns in oxygen.

Question 3

what are the products of complete combustion?

Answer 3

carbon dioxide and water.

Question 4

what is an incomplete combustion?

Answer 4

when a substance combusts, but not completely, because of a lack of oxygen.

Question 5

what are the products of incomplete combustion?

Answer 5

Always water, ans sometimes Carbon monoxide or solid carbon

Question 6

what is a pollutant?

Answer 6

when a substance causes a negative effect on the planet.

Question 7

what are the pollutants of complete combustion?

Answer 7

CO2 and H2O

Question 8

explain how CO2, and H2O lead to global warming.

Answer 8

CO2 and H20 absorb UV light from the sun, therefore the temperature on earth increases.

Question 9

What are some of the pollutants from incomplete combustion? and waht are their effects?

Answer 9

carbon monoxide, which is flammable and toxic to humans.

engines in cars produce carbon monoxide.

Solid carbon ( also called soot) can lead to smog.

Question 10

why does complete combustion, produce more energy than incomplete?

Answer 10

becuase the majority of the energy, comes from the formation of the carbon dioxide.

Question 11

why is complete combustion more efficient, than incomplete combustion?

Answer 11

Because we need to burn less fuel, tp produce the same ammount of energy.

Since we need less fuel, it is also more cheaper.

Question 12

what are the three organic compound equations that you need to remember?

Answer 12

1. CH4S + 302—->CO2+2H20+ SO2

2.CH4N+ 2.5O2—->CO2+2H2O+NO

3.CH4Si +3O2—->CO2 + 2H20 + SiO2

Question 13

what is the main problem with releasing sulfur dioxide?

Answer 13

It causes breathing proboems, and respiratory issues.

also leads to acid rain.

Question 14

How does SO2 produce acid rain?

Answer 14

SO2 + 2H2O—-> H2SO4

Question 15

What is an unburnt hydrocarbon?

Answer 15

When alkanes in petrol, dont undergo combustion, and instead are released as gases, we call them unburnt hydrocarbons.

Question 16

whay do unburnt hydrocarbons release? and what is its effects?

Answer 16

smog. it prevents sunlight from reaching crops.

Question 17

what 3 processes happen in a petrol engine? and state all the products.

Answer 17

1. incomplete combustion : C (s), CO, H2O.
2. Complete combustion: CO2, H2O.
3. unburnt hydrocarbons : smog.

Question 18

describe hiw nitric oxide forms and what it does to the environment. Include some equations in your answers.

Answer 18

Since there is alot of high heat in a petrol engine, other side reactions may occur.

-N2+O2—-> 2NO

It creates respiratory issues, and acid rain.

Question 19

what do we use in order to reduce the pollution from engines in cars?

Answer 19

catalytic converters.

Question 20

describe how a catalytic converter, helps prevent the number of unburns hydrocarbon, NO and CO.

Answer 20

unburnt hydrocarbon + O2—-> CO2 + H2O.

2NO + 2CO —-> N2 + 2CO2

Question 21

what is crude oil?

Answer 21

Oil that hasnt had its impurities removed yet. The oil still contains many different alkanes, with many different properties.

Question 22

Describe how fractional distillation is carried out, in order to separate alkanes from crude oil.

Answer 22

step 1: pass the crude oil, through a furnace.
- the furnace will turn it from a liquid to a vapour.
- step 2: This vapour then passes into the bottom of a huge collumn.
- the bottom of this collumn is super hot, but the top isnt. ( so temperature decreases as we go up a collumn).
- step 3: When the vapour reaches the temperature of its boiling point, it then condenses back into a liquid, and gets in a collection chamber in a DIFFERENT fraction.

Question 23

state what happens to the boiling point when an alkane increases in size. and waht does this mean in fractional distillation?

Answer 23

Number of wan der waals forces increases, which means that more energy required to break bond, thus higher boiling point.

It means the larger alkanes will condense, lower in the collumn.

Question 24

what is cracking?

Answer 24

The process by which we conver longer chain hydrocarbons, into shiorter chain hydrocarbons.

Question 25

Why are short chain hydrocarbons, better than long chain hydrocarbons?

Answer 25

Because they are more flammable, since they burn more easily.

Question 26

What are the two types of cracking?

Answer 26

Thermal cracking, and catalytic cracking.

Question 27

state the conditiond needed for thermal cracking, and explain each one.

Answer 27

700 - 1000 C .

700 ATM / 7000 KPa.

Because alot of energy is required to break the bond enthalpy of the carbon carbon bond.

Question 28

What are the products of thermal cracking?

Answer 28

A shorter chain alkane, and one or more alkenes.

The total number of carbons and hydrogens, should add up to 0.

Question 29

what is the main type of alkane, produced in thermal cracking?

Answer 29

Mainly linear alkanes.

Question 30

What are the conditions for catalytic cracking?

Answer 30

requires a zeolite catalyst, slight pressure
( 1ATM/100KPa), and high tmperatures. ( 525 - 750C).

Question 31

what are the main products of catalytic cracking?

Answer 31

branched alkanes, cycloalkanes, or aromatics.

Question 32

contrast catalytic VS thermal cracking.

Answer 32

thermal: expensive due to high temperatures, and pressure.
Catalytic: expensive, because zeolite needs replacing.

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Question 33

what are some catalysts used in a catalytic converter?

Answer 33

Platinum , Palladium, Rhodium, Iridium.