ES5

Question 1

Explain the feature that controls the pressure in the tanks that transport chlorine

Answer 1

Chlorine is transported as a liquid so if the temp. or pressure becomes too high, the tanks have devices that release pressure + release chlorine gas to vent the tank - better to release small amounts of gas than to have a massive explosion in case of tank failure

Question 2

Explain the feature of these transport tanks in case there is discharge of chlorine exceeding a certain limit

Answer 2

These tanks have an excess flow valve, designed to close automatically if the angle valve (which regulates the discharge of chlorine) is broken in case of an accident in transport
(Activated when discharge of liquid chlorine exceeds a certain limit)

Question 3

How do workers at chemical plants handle the chlorine stored in cylinders and what precaution is taken to make sure that the chlorine is not leaking?

Answer 3

They use a hoist to avoid damage to the outside

As a routine check they use a stick with cloth soaked in concentrated ammonia solution over the end - if cylinder is leaking then a white cloud of ammonium chloride will be seen

Question 4

What are the two main uses of chlorine?

Answer 4

• Water treatment

- Household cleaning products (bleach)

Question 5

What are the benefits of using chlorine for water treatment?

Answer 5

It kills bacteria and other pathogens
(After the introduction of chlorination of water in 20th century there was a rapid decline in no. of deaths from typhoid)

Question 6

What are the benefits of using chlorine in household cleaning products (bleach)?

Answer 6

• Kills bacteria on surfaces

- Bleach (an oxidising agent) removes stains by breaking bonds in coloured chemicals to form colourless products

Question 7

What are iodine-thiosulfate titrations used for?

Answer 7

They are used to find the concentration of a chemical that is strong enough to oxidise iodide ions