Hydrocarbons

Question 1

Define hydrocarbon.

Answer 1

A molecule that contains hydrogen and carbon ONLY!

Question 2

what is crude oil?

Answer 2

an oil that is found underground and is made from the remains of dead animals over millions of years

Question 3

how is crude oil obtained ?

Answer 3

crude oil is obtained by drilling into rocks and sucking the oil out of

Question 4

What is fractional distillation ?

Answer 4

splitting crude oil into different hydrocarbons

Question 5

steps to fractional distillation.

Answer 5

1. crude oil is boiled into a gas
2. the crude oil gas in fractionating column
3. Gas rises and condenses when in an area cooler than its boiling point
4. The condensed gas is then separated

Question 6

what is the effect of hydrocarbons with long chains?

Answer 6

it has a high boiling point

Question 7

what are the results of fractional distillation?

Answer 7

Bitumen
Heavy fuel oil
Diesel
Kerosene
Petrol

Question 8

what is cracking?

Answer 8

Cracking is where longer chain hydrocarbons are made into shorter chain more useful hydrocarbons

Question 9

cracking is described as a thermal decomposition reaction. What does this mean?

Answer 9

Thermal decomposition reaction is where we break apart the hydrocarbons with heat

Question 10

what are the two types of cracking?

Answer 10

Catalytic cracking
Steam cracking

Question 11

What are the three steps of catalytic cracking?

Answer 11

step one: heat and vaporise the long chain hydrocarbon.
Step two: get hot powdered aluminium oxide and past the vapour over it
step three: when contact is made with the catalyst (powdered aluminum oxide) it splits into two shorter chain hydrocarbons

Question 12

what are the three steps to steam cracking?

Answer 12

Step one: heat and vaporise the long chain hydrocarbon.
Step two: mix hydrocarbon with steam and heat up to a very high temperature.
Step three: the long chain hydrocarbon would split into shorter chain hydrocarbons

Question 13

what is the written reaction for cracking?

Answer 13

Long chain alkane -> shorter alkane + alkene

Question 14

when decane C(10)H(22) is cracked into ethene C(2)H(4) What is the other hydrocarbon formed?

Answer 14

C(8)H(18)

Question 15

why are Alkenes reactive?

Answer 15

alkenes are unsaturated and therefore have more particles to react with. The double bond which every alkene has can be opened up to form a new reactant with another molecule

Question 16

what is the test for Alkene

Answer 16

Poor bromine water into your solution of alkene and if orange bromine turns colourless, an alkene is present

Question 17

why can alkenes be added together to make polymers?

Answer 17

Because the double bond can break to form two or more single bonds and so the alkene bonds to adjacent molecules

Question 18

what are the three types of addition reactions with alkenes?

Answer 18

. With hydrogen
. With water
. With halogens.

Question 19

What happens in an addition reaction of a alkene when reacted with hydrogen

Answer 19

The alkene reacts with hydrogen and a catalyst and forms an alkane

Question 20

what happens in an addition reaction of an alkene when reacted with water?

Answer 20

the alkene reacts with water and a catalyst at a high temperature to form a non-pure alcohol

Question 21

what happens in an addition reaction when an alkene is reacted with a halogen?

Answer 21

similar to when reacted with hydrogen, however without the use of a catalyst.

Question 22

In addition reaction when ethene is reacted with bromine ( a halogen) what happens and what reactant is formed?

Answer 22

the ethene and bromine put into the same test tube and shaken to react with each other to form dibromoethane. this is the common test for an alkene

Question 23

why was the early atmosphere carbon dioxide rich ?

Answer 23

intense volcanic activity caused an atmosphere rich with carbon dioxide, water vapour and nitrogen

Question 24

how where the oceans formed ?

Answer 24

The water vapour in the atmosphere condensed to form the oceans and the carbon dioxide dissolved in it and became sediments on the seabed

Question 25

how did the atmosphere become carbon dioxide rich to oxygen rich?

Answer 25

About 2.7 billion years ago Aggie and green pants slowly formed which photosynthesised taking the carbon dioxide from the atmosphere in and producing oxygen.

Question 26

how is crude oil and natural gases formed?

Answer 26

Plants such as plankton die and fall to the seabed which gets trapped in sediment which then becomes solid into sedimentary rock which holds crude oil and natural gases

Question 27

when burning hydrocarbons why can complete combustion occur?

Answer 27

Some hydrogen can contain impurities such as sulphur, which therefore Causes incomplete combustion

Question 28

Explain how incomplete combustion can form carbon monoxide and it’s dangers

Answer 28

If there is not enough oxygen for the hydrocarbon to react with carbon monoxide can form due to incomplete combustion. Carbon monoxide can diffuse into the blood and bind to the haemoglobin which means less oxygen gets transported around the body.

Question 29

Explain how soot can be formed from incomplete combustion and it’s dangers

Answer 29

if there is not enough oxygen to react with the hydrocarbon soot can be formed. if inhaled this can cause respiratory problems.

Question 30

Explain how impurities in hydrocarbons can form sulphur dioxide

Answer 30

Hydrogen can have impurities in them such as sulphur which when reacted with oxygen forms sulphur dioxide

Question 31

explain how due to an incomplete combustion nitrogen oxides can be formed

Answer 31

Due to the exothermic reaction of a combustion nitrogen and oxygen in the air react to form nitrogen oxides

Question 32

how does acid rain occur?

Answer 32

Hydrocarbons which have impurities such as sulphur in them cause incomplete combustion which forms sulphur dioxide, and the exothermic reaction reacts nitrogen and oxygen in the air to form nitrogen oxides. these 2 gasses then mix with clouds and diffuse to form dilute sulfuric acid and dilute nitrous acid which the fall as acid rain