C1 - Carbon Chemistry

Question 1

Describe the cracking of liquid paraffin.

Answer 1

1. High temperature and catalyst required.
2. Larger hydrocarbon molecules split up into smaller ones.
3. This makes more petrol (in higher demand).

Question 2

Why can crude oil be separated through fractional distillation?

Answer 2

The larger the hydrocarbon molecules, the more energy that is required to overcome the intermolecular forces between these molecules. As a result, similar-sized molecules have similar boiling points; this is why they exit the distillation column at the height.

Question 3

What catalyst is used in cracking?

Answer 3

Aluminium Oxide

Question 4

What two extra products can be produced as a result of incomplete combustion?

Answer 4

Carbon Monoxide and Carbon

Question 5

What is the word equation for complete combustion?

Answer 5

Hydrocarbon + Oxygen –> Carbon Dioxide + Water

Question 6

Name three stages in the evolution of the atmosphere.

Answer 6

1. Volcanoes gave out steam and CO2
2. Green plants evolved and produced oxygen.
3. Ozone layer allows evolution of complex animals.

Question 7

Describe the chemical composition of our atmosphere:

Answer 7

78% Nitrogen, 0.035% Carbon Dioxide, 21% Oxygen

Question 8

As the earth evolved, how did nitrogen gas begin to fill the atmosphere?

Answer 8

Firstly, ammonia (released from volcanoes) reacted with oxygen to produce nitrogen. Secondly, denitrifying bacteria convert nitrates in the ground to nitrogen gas.

Question 9

Oxygen put into the atmosphere helped create the ozone layer. Why is the ozone layer important for life on earth?

Answer 9

It blocked harmful rays from the Sun and enabled more complex organisms to evolve.

Question 10

Describe the carbon cycle.

Answer 10

Carbon dioxide is put into the atmosphere through combustion, respiration and decay. Carbon dioxide is removed from the atmosphere via photosynthesising plants.

Question 11

How is acid rain caused?

Answer 11

The combustion of fossil fuels with sulfur impurities leads to sulfur dioxide being put into the air. Furthermore, combustion causes oxygen and nitrogen to react - releasing oxides of nitrogen into the air.

When these gases mix with the clouds, they form dilute sulfuric acid and dilute nitric acid. This causes acid rain.

Question 12

How is photochemical smog caused?

Answer 12

Oxides of Nitrogen combine with oxygen in the air to produce Ozone (O3). Ozone causes breathing difficulties, headaches and tiredness.

Question 13

What is the balanced symbol equations for catalytic conversion?

Answer 13

2CO + 2NO –> N2 + 2CO2

Question 14

Why does cooking mean potatoes are easier to digest?

Answer 14

Potato cells are surrounded by a rigid cell wall made up of cellulose. Humans can’t digest cellulose, so we cook potatoes to rupture their cell walls. The starch grains in the potato also swell up, making the potato softer and therefore easier to digest.

Question 15

What is the symbol equation for the thermal decomposition of sodium hydrogencarbonate?

Answer 15

NaHCO3 –> Na2CO3 + CO2 + H2O

Question 16

How do emulsifiers help oil and water to mix (to make an emulsion)?

Answer 16

The emulsifier has a hydrophilic (likes water, dislikes oil) head and a hydrophobic tail (dislikes water, likes oil). The hydrophilic end bonds to the water molecules and the hydrophobic end bonds to the oil molecules.

Question 17

What is the word equation for making an ester (perfume)?

Answer 17

Carboxylic acid + Alcohol –> Ester + Water

Question 18

Name five properties needed by perfumes.

Answer 18

1. Easily evaporates (volatile)
2. Non-toxic
3. Doesn’t react with water
4. Doesn’t irritate the skin
5. Insoluble in water

Question 19

What is a solute? What is a solvent?

Answer 19

Solute - substance that is being dissolved

Solvent - liquid it is being dissolved into

Question 20

Nail varnish doesn’t dissolve in water. Why?

Answer 20

1. The attraction between the nail varnish molecules is greater than the attraction between the nail varnish molecules and the water molecules.
2. The attraction between the water molecules is stronger than the attraction between the water molecules and the nail varnish molecules.

Question 21

How does oil paint dry?

Answer 21

The solvent evaporates and then the oil is oxidised by the oxygen in the air, forming a hard film.

Question 22

How do emulsion paints dry?

Answer 22

The water-based emulsion dries when the solvent evaporates, leaving behind the binding medium and pigment as a thin solid film.

They dry faster than oil paints.

Question 23

What determines how ‘stretchy’ or ‘bendy’ a polymer will be?

Answer 23

If there are weaker intermolecular forces between the polymer chains, the chains are free to slide over eachother and can therefore be stretched more easily.

On the other hand, if there are strong intermolecular forces, or cross-links between the layers, it is harder for the chains to slide over eachother each other. As a result, the polymer is harder to stretch.

Question 24

Explain how GORE-TEX is a breathable, yet waterproof material?

Answer 24

1. GORE-TEX is made up of a layer of expanded PTFE that is attached onto another fabric (e.g. nylon) to make it stronger.
2. The PTFE is a micro-porous membrane made up of lots of tiny holes.
3. The pours are big enough to allow water vapour to exit, but too small to allow water droplets to enter.

Hence, breathable and waterproof.

Question 25

Describe the bonding in an alkane molecule.

Answer 25

Electrons are shared between multiple hydrocarbon atoms in an alkane. This is called covalent bonding.

Question 26

Why do alkenes decolourise bromine water?

Answer 26

An alkene is an unsaturated compound, meaning it has double bonds available. As a result, an addition polymerisation reaction can occur between the bromine water and the alkene. The result of this reaction is a new colourless solution.

Question 27

As the size of the hydrocarbon molecule increases, how do its properties change?

Answer 27

1. It’s boiling point increases.
2. It gets less flammable.
3. It gets more viscous
4. It gets less volatile

Question 28

LPG exits at the top of the distillation column. What is LPG made up of?

Answer 28

Mostly propane and butane.

Question 29

What is produced as a result of cracking large alkane molecules?

Answer 29

• Smaller alkane molecules

- AND, smaller alkene molecules

Question 30

Why are perfumes volatile?

Answer 30

1. Weak forces of attraction between the particles in liquid perfume.
2. Not much energy needed to overcome those weak forces.
3. Therefore, perfume easily evaporates.
4. Hence, it is volatile.

Question 31

Why won’t the components of a colloid separate?

Answer 31

The particles are extremely small and are evenly dispersed within the solution. As a result, forces of attraction can’t cause the particles to group up and separate out from the solution.

Question 32

How can thermochromic pigments be given an even greater range of colour changes?

Answer 32

We can combine acrylic paints with thermochromic pigments to produce paints that change to a wider variety of colours when the temperature changes.