C9-C11

Question 1

Explain how alkenes are obtained from fractional distillation followed by cracking

Answer 1

In fractional distillation, the oil is vaporised before going in to the fractionating column with different boiling points per fraction. The column is cooler at the top and so that the fractions can condense at different levels, and are then collected as liquids. Heavy and fractions with more viscosity are collected at the bottom.
In cracking, the larger and heavier fractions are broken down into smaller ones. They are vaporised, passed over to a hot catalyst so large molecules can split up. The process of cracking the produces alkenes and alkanes

Question 2

describe why sulfur should be removed from petrol

Answer 2

Burning sulfur produces sulfur oxide and can cause acid rain

Question 3

many pentene molecules can join together to form

Answer 3

poly pentene / polymer

Question 4

suggest why burning hydrogen is more environmentally friendly that burning methane

Answer 4

does not pollute water
no harmful gas produced
no carbon monoxide produced

Question 5

Why do the fractions separate at different temperatures?

Answer 5

hydrocarbon have different boiling points

Question 6

give three uses of ethanol

Answer 6

• alcoholic beverages
• perfume
• fuel

Question 7

Solutions of ethanoic acid and hydrochloric acid with the same concentration
have different pH values.
Explain why the solution of ethanoic acid has a higher pH than the solution of
hydrochloric acid.

Answer 7

1. ethanoic acid is a weak acid

2. ethanoic acid does not completely ionise

Question 8

What does volatile mean?

Answer 8

evaporises easily and quickly

more likely to turn into a gas

Question 9

Name three elements petrol must contain.

Answer 9

carbon, hydrogen, and sulfur

Question 10

Describe how ethene forms poly(ethene).

Answer 10

Many ethene monomers join to form a long chain of hydrocarbons

Question 11

Poly(ethene) is a thermoplastic that softens easily when heated.
Suggest and explain how the structure of PEX changes this property.

Answer 11

PEX contains cross links and inter molecular bonds
The molecules in PEX are held tight
The chains cannot slide past each other = harder shape

Question 12

Describe how the student could show that there are chloride ions in this
solution.

Answer 12

add silver nitrate solution to observe a white percipitate

Question 13

Describe how to use the apparatus to do a titration using dilute hydrochloric acid.

Answer 13

1. put the alkali solution into the burette
2. add a few drops of indicator into the conical flask
3. swirl until the indicator becomes red
4. repeat the process to discard any anomalous results
5. use a white background for a clear observation

Question 14

Explain why burning biofuels contributes less to climate change than burning
fossil fuels.

Answer 14

plants take in CO2 by photosynthesis while burning fossil fuels emit CO2

Question 15

Give one problem caused by non-biodegradable polymers.

Answer 15

They do not decompose

more landfill sites are required