C7: Organic chemistry Flashcards Preview

TRIPLE Chemistry GCSE 2020 > C7: Organic chemistry > Flashcards

Flashcards in C7: Organic chemistry Deck (65)
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1

What makes something "organic" in the chemical sense?

It contains carbon.

2

What is crude oil?

• A finite resource found in rocks: the remains of an ancient biomass, consisting mainly of plankton that was buried in mud.

• Is a mixture of a large number of compounds, mostly hydrocarbons.

3

What are hydrocarbons?

Molecules made only of hydrogen and carbon.

4

Most of the hydrocarbons in crude oil are what?

Alkanes.

5

What is the general formula for alkanes?

CnH2n + 2

6

What is meant by the term "homologous series"?

A series of compounds with the same functional group and similar chemical properties. 

7

What are the names of the first four members of the alkanes?

• Methane

• Ethane

• Propane

• Butane

8

What is fractional distillation and what is its purpose?

• The process by which hydrocarbons in crude oil are separated into fractions.

• The fractions can be processed to produce fuels and feedstock for the petrochemical industry.

9

Explain how the process of fractional distillation works.

• Crude oil is heated until the hydrocarbons evaporate.

• The hydrocarbons rise through the column.

• The hydrocarbons condense and different fractions are extracted in different parts of the column.

• Longer hydrocarbons condense in the lower parts of the column; shorter ones in the upper parts.

10

Name 5 fuels produced by fractional distillation from crude oil.

• Petrol

• Diesel oil

• Kerosene

• Heavy fuel oil

• Liquefied petroleum gases

11

Name 4 useful materials produced by the petrochemical industry.

• Solvents

• Lubricants

• Polymers

• Detergents

12

Why is there such a vast array of natural and synthetic carbon compounds?

Carbon atoms have the ability to form families of similar compounds (homologous series).

13

What 3 properties of hydrocarbons depend on the size of molecules?

• volatility (boiling points)

• viscosity (runniness)

• flammability

14

For hydrocarbons, how does boiling point change with increasing molecular size?

• Longer hydrocarbon chains have more cumulative intermolecular forces which require more energy to overcome

• So their boiling points are higher

• Shorter chains have less cumulative intermolecular forces, so it takes less energy to separate molecules

• So they are more volatile

15

For hydrocarbons, how does viscosity change with increasing molecular size?

• Longer hydrocarbon chains have more cumulative intermolecular forces which require more energy to overcome

• So they are more viscous

• Shorter chains have less cumulative intermolecular forces, so it takes less energy to separate molecules

• So they are less viscous

16

For hydrocarbons, how does flammability change with increasing molecular size?

• Longer hydrocarbon chains have more cumulative intermolecular forces which require more energy to overcome

• So they are less flammable

• Shorter chains have less cumulative intermolecular forces, so it takes less energy to separate molecules

• So they are more flammable

17

What happens during the combustion of hydrocarbons?

• The carbon and hydrogen in the fuels are oxidised

• Energy is released

18

Write the general equation for the complete combustion of a hydrocarbon.

Hydrocarbon + oxygen → carbon dioxide + water

19

What are alkenes?

Hydrocarbons with the functional group C=C (with a double carbon-carbon bond). 

20

What is cracking and what is its purpose?

• The process by which long-chain hydrocarbons are broken down to produce smaller, more useful molecules by thermal decomposition

• The products of cracking are alkanes and alkenes

• Some of the products of cracking - the small ones - are used for fuels because they are flammable

21

How are alkenes (produced by cracking) useful?

• Used to produce polymers

• Used as starting materials for the production of many chemicals

22

Name 2 types of cracking.

• Catalytic cracking

• Steam cracking

23

Describe the conditions used for catalytic cracking.

• It is a thermal decomposition reaction

• Long-chain hydrocarbons are heated and vaporised

• Vapour is passed over a powdered aluminium oxide catalyst

• The molecules split apart on the surface of the specks of catalyst

24

Describe the conditions used for steam cracking.

• It is a thermal decomposition reaction

• Long-chain hydrocarbons are heated and vaporised

• Vapour is mixed with steam and heated to a very high temperature

• The molecules split apart

25

Which are more reactive: alkanes or alkenes?

Alkenes.

26

How would you test for alkenes?

• Add bromine water, which is bright orange

• Positive result: solution goes colourless

27

What is the general formula for alkenes?

CnH2n

28

Which out of alkanes and alkenes are saturated and unsaturated? Explain why.

Alkanes are saturated because all C-C bonds are single.

Alkenes are unsaturated because they contain a double C-C bond (C=C).

29

What are the names of the first four alkenes?

• Ethene

• Propene

• Butene

• Pentene

30

How do alkenes combust?

• Alkenes can react completely with oxygen in the same way as all hydrocarbons.

• But they tend to react incompletely, burning with a smoky flame.