5. Chemistry In Industry

Question 0

write ionic half-equations for the reactions at the electrodes in the diaphragm cell

Answer 0

2 Cl- > Cl2 + 2e-

2 H+ + 2e- > H2

Question 1

describe important uses of sodium hydroxide; and of chlorine.

Answer 1

Sodium Hydroxide: Bleach; paper; soap

Chlorine: sterilising water; bleach; hydrochloric acid

Question 2

describe the manufacture of sodium hydroxide and chlorine by the electrolysis of concentrated sodium chloride solution (brine) in a diaphragm cell

Answer 2

Brine is NaCl solution.

In electrolysis, chlorine is created at the anode, hydrogen is created at the cathode, sodium hydroxide is left in the solution.

2NaCl + 2H2O > 2NaOH + H2 + Cl2

This happens in a diaphragm cell.

Question 3

describe the use of sulfuric acid in the manufacture of detergents, fertilisers and paints

Answer 3

Detergents: used to ‘sulphonate’ products (apperently.)

Fertilisers: reacted to make phosphates soluble to plants: reacted to make ammonia easier to handle.

Paints: reacted with titanium ore to make a main pigment in paint.

Question 4

describe the manufacture of sulfuric acid by the contact process, including the essential conditions(temperature,pressure,catalyst)

Answer 4

(stage 1) S + 2O > SO2
(stage 2) SO2 + O > SO3
(stage 3) SO3 + H2O > H2SO4

i) a temperature of about 450C
ii) a pressure of about 2 atmospheres
iii) a vanadium(V) oxide catalyst (in stage 2)

Question 5

recall the raw materials used in the manufacture of sulfuric acid

Answer 5

Sulphur (sulphur is found in rocks and some natural gasses) and oxygen from the air.

Question 6

describe the use of ammonia in the manufacture of nitric acid and fertilisers

Answer 6

Ammonia is put into fertilisers - it contains nitrate ions plants need to make amino acids and so proteins plants need to grow.

Ammonia is also reacted with oxygen to produce nitric acid:
4NH3 + 8O2 > 4HNO3 + 4H2O

Question 7

understand how the cooling of the reaction mixture liquefies the ammonia produced and allows the unused hydrogen and nitrogen to be recirculated

Answer 7

The products from the reactant are sent through a cooling mechanism, this is at a temperature that condenses ammonia, but not hydrogen and nitrogen. Liquid ammonia is then collected but hydrogen and nitrogen float right back into the reactor.

Question 8

describe the manufacture of ammonia by the Haber process, including the essential conditions (temperature, pressure, catalyst)

Answer 8

i) a temperature of about 450°C
ii) a pressure of about 200 atmospheres
iii) an iron catalyst

Question 9

Which products are used in the manufacture of ammonia?

Answer 9

Ammonia is made by reacting nitrogen from the air and hydrogen (which comes as a natural gas or from cracking hydrocarbons.)

Question 10

What does condensation polymerisation produce?

Answer 10

Two monomers come together by loosing a molecule. Atoms from each monomer join together to make the molecule: commonly a H atom from one and a OH molecule from another form water. The two monomers then join together, making a polymer.

Question 11

explain why addition polymers are hard to dispose of.

Answer 11

Polymers are saturated so they don’t react. This means they don’t decompose easily.

addition polymers are hard to dispose of as their inertness means that they do not easily biodegrade.

Question 12

describe some uses for polymers, including poly(ethene), poly(propene) and poly(chloroethene)

Answer 12

polyethene: plastic carrier bags; plastic bottles
polypropene: crates; ropes
polychlroethene: piping; cable insulation.

Question 13

deduce the structure of a monomer

Answer 13

A monomer that is repeated in a polymer looks much like the repeat unit; apart from, instead of having an empty bond either end, it has a double bond in the middle.

Question 14

What is an addition polymer formed by?

Answer 14

An addition polymer is formed by joining up many small molecules called monomers.

monomers are alkenes with a double bond. If this bond is broken there can be other things bonded, if a carbon from another monomer is bonded in then you can create a chain; do this many times can you have a polymer.

Question 15

describe how long-chain alkanes are converted to alkenes and shorter-chain alkanes by catalytic cracking?

Answer 15

Long chain hydrocarbons are passed over a hot catalyst (silica or alumina at 600-700 degrees) this causes them to break down into smaller molecules.

As some atoms are lost from molecules, they become unsaturated and can therefore from a double bond. This is how you get alkenes from the process as well as shorter chain alkanes.

Question 16

What does fractional distillation of crude oil produce?

Answer 16

Long chain hydrocarbons are less flammable and more viscous.
Short chain hydrocarbons burn well and flow well.

Long chain hydrocarbons can be cracked which breaks them up into short chain ones.

Question 17

What do nitrogen oxides and sulfur dioxide (pollutant gases) contribute to?

Describe the problems caused by acid rain

Answer 17

NO and SO2 are given off into the atmosphere by some industrial processes.

When they are in the atmosphere they react with rain water to create H+ ions.

When the rain falls the acid can corrode rocks and buildings. Acid can also alter the PH in soil or rivers which can effect an ecosystem.

Also acid rain corrodes limestone, which damages buildings and stuff.

Question 18

understand that, in car engines, the temperature reached is high enough to allow nitrogen and oxygen from air to react, forming nitrogen oxides

Answer 18

In car engines there is a high enough temperature to cause a reaction between oxygen and nitrogen in the air.

This makes NO.

Question 19

What does incomplete combustion of fuels produce?

Why is carbon monoxide poisonous?

Answer 19

Hydrocarbons (from crude oil) + oxygen > carbon dioxide + water

Unless there is not enough oxygen around. Then fuels will combust incompletely:

Hydrocarbons + oxygen > carbon monoxide + carbon + water

Carbon monoxide combines with heamaglobin in red blood cells, meaning they can’t carry oxygen around the body. It reduces the capacity of the blood to carry oxygen.

Question 20

describe the trend in boiling point and viscosity of the main fractions

Answer 20

Fractions with low boiling points are less viscous.

Fractions with high boiling points are more viscous.

Question 21

describe and explain how the industrial process of fractional distillation separates crude oil into fractions

Answer 21

Crude oil is heated until it boils. As a gas it floats upwards.
As the gas goes higher up and further from the heat source the temperature decreases.
When a compound reaches it condensing point it will condense into a liquid and be collected.
This is known as fractional distillation, and groups with similar condensing temperatures are known as fractions; each fraction is a different substance.

Question 22

Define:

Viscosity

Answer 22

Viscosity is a measure of a fluid’s resistance to flow. It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion.

E.g. Imagine a styrofoam cup with a hole in the bottom. If I then pour honey into the cup I will find that the cup drains very slowly. That is because honey’s viscosity is large compared to other liquids’ viscosities. If I fill the same cup with water, for example, the cup will drain much more quickly.

Question 23

Define:

Monomer

Answer 23

A monomer is the simplest unit, or the repeating unit, of a polymer.

A monomer may combine with another monomer through chemical bonds to form a larger molecule, as in a polymer.

Examples of monomers are amino acids that link together by a peptide bond forming a polypeptide or protein.

Question 24

Define:

Polymer

Answer 24

A polymer is a large molecule made up of chains of linked monomer units.

Polymers usually have high melting and boiling points.