Topic 6 - Organic Chemistry

Question 1

isomers

Answer 1

molecules that have the same molecular formula but different structural formulas

(they are made of the same atoms, only arranged differently)

Question 2

alkanes

Answer 2

hydrocarbons with only single bonds

Question 3

homologous series

Answer 3

group of molecules/compounds with similar chemical properties and the same general formula

Question 4

hydrocarbon

Answer 4

substance that contains only hydrogen and carbon

Question 5

hydrocarbon + oxygen —>

Answer 5

carbon dioxide + water

Question 6

is combustion endothermic or exothermic?

Answer 6

exothermic

Question 7

during combustion, are carbon and hydrogen oxidised or reduced?

Answer 7

oxidised

Question 8

crude oil

Answer 8

mixture made of many different componentsm mostly hydrocarbons with different boiling points

it is a fossil fuel

Question 9

how is crude oil made?

Answer 9

• from dead remains of plants and animals, specifically plankton
• these remains were covered by mud and sand and buried in the earth
• over millions of years, the remains were compressed under heat and pressure
• the heat and pressure chemically changed the remains into crude oil

Question 10

how fractional distillation of crude oil works

Answer 10

1. heat crude oil to very high temp so all compounds are evaporated to gas
2. hot gaseous hydrocarbons rise up the column
3. as they rise, they cool down as the top of the column is cooler than the bottom
4. hydrocarbons will then condense as they have cooled down, collecting in trays
5. the longer chain hydrocarbons condense at the bottom as they have higher boiling points
6. the shorter chain hydrocarbons condense at the top as they have lower boiling points

Question 11

components of crude oil

Answer 11

petrolium gas, petrol, kerosene, diesel, heavy fuel oil, bitumen

Question 12

cracking

Answer 12

process in which larger chain hydrocarbons are split into smaller, more useful hydrocarbons

Question 13

catalytic cracking

Answer 13

1. long chain alkanes are heated until they vaporise into gas
2. they’re passed over a hot, powdered aluminium oxide catalyst
3. this breaks the long chain alkanes into a small chain alkane and an alkene

Question 14

steam cracking

Answer 14

• no catalyst involved
• vaporised long chain alkane is mixed with steam at very high temperatures

Question 15

how can we distinguish between alkanes and alkenes?

Answer 15

• bromine water test.
• by itself, bromine water is orange
• when mixed with alkenes, it turns colourless
• when mixed with alkanes, it stays orange

Question 16

equation for complete combustion of a hydrocarbon

Answer 16

hydrocarbon + oxygen —> carbon dioxide + water

Question 17

what does incomplete combustion form?

Answer 17

small particles of carbon

called soot

Question 18

negative effects of soot

Answer 18

• causes smog which reflects light into space
• damages lungs and causes disease
• forms carbon monoxide

Question 19

why is carbon monoxide harmful?

Answer 19

• binds to haemoglobin, meaning oxygen cannot be transported around the body
• this can cause fainting, coma and death

Question 20

what forms acid rain?

Answer 20

sulfur dioxide & nitrogen oxides

Question 21

impacts of acid rain

Answer 21

damages buildings and statues

makes soil acidic, affecting plants

Question 22

alkenes

Answer 22

hydrocarbons with a C=C double bond

Question 23

alcohol functional group

Answer 23

OH

COOH group

Question 24

pH of alcohols

Answer 24

7 (neutral)

Question 25

uses of alcohols

Answer 25

• fuel
• as a solvent in industry

Question 26

characteristics of alcohols

Answer 26

• flammable
• soluble
• oxidised by carboxylic acids