12. Sulfur

Question 1

Where can sulfur be found in its elemental state?

Answer 1

Sulfur is found in its elemental state underground in the USA, Mexico and Poland

Question 2

How can sulfur be obtained as a by product?

Answer 2

It is also a by-product from the removal of sulfur from petroleum and natural gas

Question 3

In what ores can sulfur be found?

Answer 3

Sulfur can also be obtained from sulfide ores

Question 4

What are the main uses of sulfur?

Answer 4

• in making sulphuric acid

- in making rubber tires more flexible (vulcanising)

Question 5

Why is sulphuric acid important?

Answer 5

is a very important chemical used in many industries

Question 6

What does vulcanising consist of?

Answer 6

the rubber tyre is heated with sulfur to make it more flexible

Question 7

How can sulfur dioxide be made?

Answer 7

Sulfur dioxide can be made by the direct combination of sulphur with oxygen

Question 8

What are 2 uses of sulfur dioxide?

Answer 8

As a bleach in the manufacture of wood pulp for paper

As a preservative for foods and drinks by killing bacteria

Question 9

How are sulfites used?

Answer 9

Sulfites are often added to foods and these release sulfur dioxide in acidic conditions

Question 10

1. How can sulphuric acid be made?

contact process

Answer 10

Sulfuric acid is synthesised by the Contact process

Question 11

2. What is used in the contact process?

contact process

Answer 11

which use sulfur and oxygen from air

Question 12

3. how many stages does the contact process have?

contact process

Answer 12

3

Question 13

4. What is the first stage?
   Give CE

contact process

Answer 13

The first stage is the oxidation of sulfur:

S + O2 → SO2

Question 14

5. What is the second stage?
   Give CE

contact process

Answer 14

The main stage is the oxidation of sulfur dioxide to sulfur trioxide

2SO2 + O2 ⇌2SO3

Question 15

6. What catalyst is used in the second stage?

contact process

Answer 15

uses a V2O5 catalyst

Question 16

7. In which stage do the conditions need to be considered?

contact process

Answer 16

The conditions for the main stage of production of sulfur trioxide need to be considered

Question 17

8. What temperature and pressure need to be kept in stage 2?

contact process

Answer 17

Temperature - 450 degrees C

Pressure - 2 atm

Question 18

9. Why, in terms of equilibrium, is the temperature 450ºC?

contact process

Answer 18

The reaction is exothermic, so increasing the temperature shifts the position of equilibrium to the left in the direction of the reactants

Therefore the higher the temperature, the lower the yield of sulfur trioxide

Question 19

10. What is 450ºC a compromise between?

contact process

Answer 19

The optimum temperature is a compromise between a higher rate of reaction at a higher temperature and a lower equilibrium yield at a higher temperature

Question 20

11. Why, in terms of equilibrium, is the pressure 2atm?

contact process

Answer 20

An increase in pressure shifts the position of equilibrium to the right in the direction of a smaller number of gaseous molecules

However the position of equilibrium lies far to the right (the equilibrium mixture contains about 96% sulfur trioxide)

Question 21

12. Why, in terms of manufacture, is the pressure 2atm?

contact process

Answer 21

So the reaction is carried out at just above atmospheric pressure because:

a) it is not worth spending the extra energy or money required to produce high pressures
b) a higher pressure would increase the problems of dealing with the corrosive mixture of gases

Question 22

13. What is produced during stage 3?

Give CE

contact process

Answer 22

Once stage 2 is completed, the sulfur trioxide is absorbed into a solution of 98% sulphuric acid to produce a thick liquid called oleum:

SO3 + H2SO4 → H2S2O7

Question 23

14. Why is the sulfur trioxide dissolved into sulphuric acid and not, for example, water?

contact process

Answer 23

It is not absorbed into water because a fine mist of sulfuric acid would be produced and this would be difficult to condense and is also highly dangerous

Question 24

15. What is oleum then dissolved into?

Give CE

contact process

Answer 24

Oleum is added to water to form concentrated sulfuric acid:

H2S2O7 + H2O → 2H2SO4

Question 25

What type of acid is sulphuric acid?

Answer 25

Sulfuric acid is a strong dibasic acid

Question 26

What is a dibasic acid?

Answer 26

two of its hydrogen atoms can be replaced by a metal

Question 27

Give CE for reaction between zinc oxide and sulphuric acid

Answer 27

ZnO + H2SO4 → ZnSO4 + H2O

Question 28

Give CE for reaction between magnesium and sulphuric acid

Answer 28

Mg + H2SO4 → MgSO4 + H2

Question 29

Give CE for reaction between sodium carbonate and sulphuric acid?

Answer 29

Na2CO3 + H2SO4 → Na2SO4 + CO2 + H2O

Question 30

What 3 properties does concentrated sulphuric acid have?

Answer 30

Concentrated sulphuric acid is corrosive, a powerful oxidising agent and a powerful dehydrating agent

Question 31

What does it mean if sulphuric acid is a good dehydrating agent?

Answer 31

it is very good at removing water from other substances

Question 32

What will happen when sugar is mixed with concentrated sulphuric acid?

Answer 32

For example, if mixed with sugar (C6H12O6), concentrated H2SO4 will remove water molecules and leave behind carbon in a spectacular looking reaction that produces a tower of pure carbon

Question 33

What are 2 uses of dilute sulphuric acid?

Answer 33

Used as a catalyst in many organic reactions

Also used as to clean the surface of metals

Question 34

What are 6 uses of concentrated sulphuric acid?

Answer 34

used in making:

• phosphate fertilisers
• soaps
• detergents
• acid drain cleaners
• used in the production of paints and dyes