Topic 8

Question 1

8.1
What is a hydrocarbon?

Answer 1

-Compound
-ONLY…
-C & H₂ atoms

Question 2

8.2
What is crude oil?

Answer 2

-Complex mixture of hydrocarbons (C atoms = in chains/rings)
-Finite resource
-Important source for useful substances e.g. fuels for vehicles, aircraft, ships, power stations; feedstock (raw materials) for petrochemical industry

Question 3

8.2
Describe the formation of crude oil

Answer 3

-Sea animals die -> fall into sea bed (don’t decay)
-Sand + mud (sediment) form on top
-↑ pressure + temp turns them into crude oil
-Takes millions of yrs

Question 4

8.2
Hydrocarbons can be arranged in chains and rings. Why?

Answer 4

-Each C atom forms 4 cov bonds
-C can be arranged in diff ways

Question 5

8.3
Why does crude oil need to be separated?

Answer 5

Useless

Question 6

8.3
Explain the process of separating crude oil into more useful mixtures

Answer 6

-Fractional distillation
-Heat oil -> liquid (w/ lowest bp) evaporates
-Gas enters column & reaches top -> cools & condenses -> collected as liquid
-Liquid w/ highest bp doesn’t condense

Question 7

8.4
Name the compounds formed from the separation of crude oil starting with the coolest

Answer 7

-LPG (liquid petroleum gas)
-Petrol
-Kerosene
-Diesel
-Fuel oil
-Bitumen

Question 8

8.4
State a use of LPG

Answer 8

Domestic heating & cooking

Question 9

8.4
State a use of petrol

Answer 9

Fuel for cars

Question 10

8.4
State a use of kerosene

Answer 10

Fuel for aircrafts

Question 11

8.4
State a use of diesel

Answer 11

Fuel for trains & some other vehicles

Question 12

8.4
State 2 uses of fuel oil

Answer 12

-Fuel for large ships
-Power stations

Question 13

8.4
State a use of bitumen

Answer 13

Surface roads & roofs

Question 14

8.5
Define the term ignition

Answer 14

Setting something on fire

Question 15

8.5
Define the term viscosity

Answer 15

How thick/runny substance is (↑ viscosity = does NOT flow easily)

Question 16

8.5
Compare the compounds in crude oil fractions

Answer 16

Top
-Small molec (less H & C atoms)
-↓ bp
-Ignite easily
-↓ viscosity
Bottom
-Large molec
-↑ bp
-Don’t ignite easily
-↑ viscosity
Darker as go down

Question 17

8.6
What are alkanes?

Answer 17

-CnH2n+2
-Homologous series of hydrocarbons w/ single cov bond
-Saturated (means single bond)

Question 18

8.6
What are alkenes?

Answer 18

-CnH2n
-Homologous series of hydrocarbons w/ C to C double cov bond
-Unsaturated

(Note: can only have 1 double bond)

Question 19

8.6
What is the homologous series?

Answer 19

Series of compounds
-Same general formula
-Molecular formula of neighbouring compounds differ by CH2
-Gradual variation in physical properites
-Similar chemical properties

(Note: Top 2 = top ans)

Question 20

8.6
What is a saturated hydrocarbon? [3 marks]

Answer 20

-Single cov bond
-ONLY
-H & C atoms

Question 21

8.6
What are most of the compounds in crude oil?

Answer 21

Alkanes

Question 22

8.6
Why is there no methene?

Answer 22

-Only 1 C atom
-No C to C double bond

Question 23

8.6
Propane and propene are bubbled through separate samples of bromine water. Describe what would happen to the bromine water

Answer 23

-Bromine = yellow/orange
-(when added to) Propane: Stays same
-Propene: decolourises from orange -> colourless

Question 24

8.7
Define the term combustion

Answer 24

Process of burning something

Question 25

8.7 Describe the complete combustion of hydrocarbon fuels. State the equation

Answer 25

-Products = Co₂ + water -E given out Hydrocarbon + oxygen -> carbon dioxide + water

Question 26

8.7 Why does the Bunsen burner have a blue flame when the air hole is open?

Answer 26

Lot of O₂ present

Question 27

8.8 a) When does incomplete combustion of hydrocarbons occur? b) What are the products?

Answer 27

a) Limited supply of O₂ b) Water, C (soot), CO, CO₂

Question 28

8.8 Explain why the incomplete combustion of hydrocarbons produces carbon and carbon monoxide

Answer 28

Not enough O₂ to turn C into CO₂

Question 29

8.9 Explain how carbon monoxide behaves as a toxic gas

Answer 29

-Colourless, odourless, toxic gas -Haemoglobin prefers to pick up CO -Not enough O₂ for respiration -Death

Question 30

8.10 State 2 effects of soot (carbon)

Answer 30

-Dirty walls -Aggravate respiratory problems

Question 31

8.11 Explain 2 ways acid rain is formed

Answer 31

-Burn fuel -> sulfur impurities react w/ O₂ -> sulfur dioxide -Dissolves in rain water -> sulfuric acid (acid rain) -Car engines -> nitrogen reacts w/ O₂ -> nitrogen dioxide -Dissolves in rain water -> nitric acid (acid rain)

Question 32

8.12 State 3 effects of acid rain

Answer 32

-Kill fish -Kill trees -Damage buildings

Question 33

8.13 Explain why oxygen and nitrogen react to produce oxides of nitrogen in car engines (internal combustion engines)

Answer 33

-Fuel mixes w/ air & ignited in engine ->↑ temp -O₂ + N collide more -> react

Question 34

8.14