C3 - Chemicals in Our Lives: Risks and Benefits

Question 1

A food company needs to buy in some salt - should it get rock salt or brine salt?

Answer 1

It should get brine salt because it will leave insoluble materials behind.

If the company was a gritting company, it should use rock salt as it’s more effective when extracted as a solid, mixed with grit and sand.

Question 2

Name two ways in which extracting salt can affect the environment.

Answer 2

• Dissolving underground salt deposits using water can lead to the ground subsiding, and possibly buildings collapsing!
• Salt waste can affect plants and animals by drying them up, through the process of osmosis.

Question 3

Name 4 uses of alkalis.

Answer 3

• Neutralising acidic soils.
• Making chemicals that bind dyes to cloth.
• Making soaps from fats and oils.
• Making glass.

Question 4

How were alkalis previously extracted?

Answer 4

From burnt wood or stale urine.

Question 5

Discuss how the Le Blanc Method was not an environmentally friendly way of making alkalis.

Answer 5

Alkalis were need on a large scale during the industrial revolution in the 1700’s for purposes such as glass.

Salt (Sodium chloride), chalk or limestone and coal are used to produce the alkali sodium carbonate (Na₂CO₃).

1T of sodium carbonate produces 2T of solid waste (CaS) and 1T of HCl gas (Hydrogen chloride).

CaS reacts with H to produce H₂S (Hydrogen Sulfide), a toxic gas that smells foul.

HCl is denser than air and is a strong acid, which pollutes the ground. It is corrosive. It can cause breathing problems, increased heartrate and even death.

Question 6

Discuss the modern way of producing alkalis.

Answer 6

We now use Electrolysis with Sodium Chloride Solution (Brine, NaCl) to produce Sodium Hydroxide (NaOH).

• Hydrogen gas (H+) is produced at the negative cathode.
• Chlorine gas (Cl-) is produced at the positive annode.

Molten sodium hydroxide solution forms at the bottom of the electrolysis chamber.

Question 7

What alkali does the Le Blanc Method produce, compared to the alkali Electrolysis produces?

Answer 7

• The Le Blanc Method produces Sodium Carbonate (Na₂CO₃).
• The Electrolysis Method produces Sodium Hydroxide (NaOH).

Question 8

Give three reasons why chemicals can be dangerous.

Answer 8

• They can last in the environment for a very long time.
• They can be carried long distances in the atmosphere, rivers and oceans.
• They can accumulate in food chains and animal tissues.

Question 9

Sulfur dioxide can be removed by reacting it with Calcium Hydroxide.

This makes a solid product and water.

What is the solid product?

Answer 9

Calcium sulfate.

Question 10

The reaction between Calcium Hydroxide and Sulfur Dioxide happens because Calcium Hydroxide is ___________.

Answer 10

Calcium Hydroxide is alkaline.

Question 11

To remove sulfur dioxide, we can use limestone.

This process makes a solid product and carbon dioxide - suggest a disadvantage to this process.

Answer 11

The carbon dioxide is a pollutant/adds to global warming/the greenhouse effect.

Question 12

What does the process of Electrolysis involve?

Answer 12

Using an electric current to bring about a chemical change and make new materials.

Question 13

What are the 3 chemicals produced through the electrolysis of NaCl, Sodium Chloride.

Answer 13

• NaOH.
• H+.
• Cl-.

Question 14

What geological processes can we use to show how the surface of the Earth has changed.

Answer 14

• Mountain building.
• Erosion.
• Sedimentation.
• Dissolving.
• Evaporation.
• Rock folding.
• Fossils.
• Magnetic clues.

Question 15

Sodium hydroxide is produced through the electrolysis of brine. Name 4 properties of it.

Answer 15

• It is an important alkali.
• It is used to make soaps, detergents, paper and textiles.
• It is used as a domestic drain cleaner.
• It is a corrosive substance.

Question 16

Hydrogen is produced through the electrolysis of brine. Name 3 properties of it.

Answer 16

• It is a flammable gas.
• It is used in processing hydrocarbon fuels, making margarine, and making ammonia in the Haber process.
• It will be used as a clean fuel in the future.

Question 17

Chlorine is produced through the electrolysis of brine. Name 3 properties of it.

Answer 17

• It can be used as a bleach.
• It can be used to kill bacteria in drinking water.
• It is a toxic gas.

Question 18

What are the 4 factors which must be assessed in a LCA (Life cycle assessment).

Answer 18

• Making the material from natural raw materials.
• Manufacture process.
• Use.
• Disposal.

Question 19

What must we use to assess the risk of using a chemical?

Answer 19

• Estimate the chance of being hurt.
• Estimate the severity of consequences if we do get hurt.
• Are the effects short-term (More likely to take the risk) or long-term (Less likely).

Question 20

Explain how we can use magnetism in rocks to track the movement of continents?

Answer 20

The crust wasn’t all formed at one point, it is formed at different angles, which are inverted approx. every 2,000 years.

Magnetite in the lava can be magnetised in a fixed direction once the rock has cooled and solidified.

Question 21

What are the environmental impacts of Electrolysis?

Answer 21

• The cost of electricity - a lot of electricity is required for the electrolysis process.
• Fossil fuel pollution (from electricity generated) produces CO₂, and contributes to global warming.

Question 22

Name a positive and negative to treating water with chlorine.

Answer 22

• [PRO] Kills water bourne diseases such as cholera and typhoid through chlorination.
• [CON] Chlorine can react and generate compounds in water that could lead to risk of cancer.

Question 23

What are the 3 methods of salt extraction?

Answer 23

• Evaporation.
• Mining.
• Solution mining.

Question 24

Explain the Evaporation process.

Answer 24

• 1 ton of salt can be made from 3 tons of wood.
• Sea water is accessible.
• Sun to collect water.
• More sustainable.
• Easy.
• Natural, contains Iodine.
• Health benefits.
• Sea salt.

Question 25

Explain the Mining process.

Answer 25

• 1 million tonnes/year.
• Used for roads/paths.
• Machine digger.
• Pillar tunnel system used to prevent cave in.
• Mines from inland seas.
• Rock salt.

Question 26

Explain the Solution Mining process.

Answer 26

• Water is pumped down into the salt bed/mine to dissolve the salt.
• The brine is pumped as a salt solution back to the surface.
• At salt works, the water is evaporated and re-used, leaving you with NaCl solid.
• Danger of surface subsidence.
• “Nature reserve” due to soft ground.