Topic 4.1-4.12 - Obtaining and Using metals

Question 1

How would you deduce that a metal is very reactivity by its reactions?

Answer 1

The most reactive metals will react with cold water and form the products of a metal hydroxide (forming an alkaline solution) and hydrogen gas

Question 2

How would you deduce that a metal is fairly reactive by its reactions?

Answer 2

Fairly reactive metals react with acids to form a salt + a hydrogen

Question 3

How would you deduce that a metal is not that reactive by its reactions?

Answer 3

Almost all metals react with oxygen to form a metal oxide, though the most reactive metals will react with oxygen more quickly.

Question 4

Which metal does not react with cold water, acids or oxygen?

Answer 4

Gold, as it is extremely unreactive

Question 5

How can you see if one metal is more reactive than another?

Answer 5

By using displacement reactions.
When a salt of the less reactive metal is in the solution, the more reactive metal gradually disappears as it forms a solution and the less reactive metal coats the surface of the more reactive metal.

Question 6

Explain displacement reactions as redox reactions

Answer 6

A more reactive metal forms a cation as they displace the less reactive metal, losing electrons and therefore being oxidised. It forms an ion as it replaces the less reactive metal in the salt solution.

Less reactive metals form atoms from negative ions as they are displaced, gaining electrons and therefore being reduced. It forms an atom as it is replaced in the salt solution.

Question 7

Explain the reactivity of metals

Answer 7

When metals react with other substances, metal atoms form positive ions. The reactivity of a metal is related to its tendency to form positive ions, more reactive metals can form positive ins more easily.

Question 8

Order the reactivity series

Answer 8

Potassium is the most reactive and reacts with water & with dilute acid
Sodium reacts with water & with dilute acid
Calcium reacts with water & dilute acid
Magnesium reacts with dilute acid
Aluminium reacts with dilute acid
Carbon reacts with dilute acid
Zinc reacts with dilute acid
Iron reacts with dilute acid
Hydrogen
Copper
Silver
Gold is the least reactive

Question 9

Where, and in what state, are most metals found?

Answer 9

Most metals are extracted from ores found in the Earth’s crust

Question 10

How are many certain types of metals found?

Answer 10

Unreactive metals are found in the Earth’s crust as uncombined elements

Question 11

Explain oxidation and reduction

Answer 11

Oxidation is the gain of oxygen.
Reduction is the loss of oxygen.

Question 12

What does the extraction of metal involve?

Answer 12

The extraction of metals involves reduction of ores

Question 13

Why can’t aluminium be extracted using carbon like some other metals?

Answer 13

Aluminium is above carbon in the reactivity series, so it is too reactive to be reduced by carbon alone.

Question 14

Why are carbon electrodes used in the electrolysis of aluminium oxide?

Answer 14

Carbon electrodes are used because they are good conductors of electricity and can withstand the high temperatures required for the process.

Question 15

Why do carbon electrodes need to be replaced during the electrolysis of aluminium oxide?

Answer 15

They react with oxygen to form carbon dioxide, which wears them away.

Question 16

Why is electrolysis of aluminium oxide conducted using cryolite?

Answer 16

Cryolite acts as a solvent and lowers the melting point, reducing energy costs.

Question 17

Why is the electrolysis of aluminium considered an expensive process?

Answer 17

Electrolysis of aluminium is expensive due to the high energy costs associated with melting aluminium oxide and maintaining the electrical current required for the process.

Question 18

Describe extraction by heating with carbon

Answer 18

Iron oxide loses oxygen and is therefore reduced. The carbon gains oxygen and is therefore oxidised. For iron, this is carried out at high temperatures in a blast furnace.

This can only be done if the metal is less reactive so that carbon displaces the metal from the ore.

Question 19

Evaluate phytoextraction

Answer 19

Some plants absorb metal compounds through their roots. They concentrate these compounds into their shoots and leaves. The plants can be burned to produce an ash that contains the metal compounds.

Question 20

Evaluate bacterial extraction

Answer 20

Some bacteria absorb metal compounds and produce solutions called leachates which contain them. Scrap iron can be used to obtain the metal from the leachate.

Question 21

Explain how a metal’s relative resistance to oxidation is related to its position in the reactivity series

Answer 21

The less reactive a metal is, the more resistant it is to oxidation. This is because for a metal to react, it forms a positive metal ion by losing electrons.

Question 22

What are the environmental and economic advantages of recycling metal?

Answer 22

● Recycling​ ​is​ ​important​ ​to​ ​achieve​ ​sustainable​ ​development
○ Requires​ ​less​ ​energy​ ​to​ ​melt​ ​and​ ​remould​ ​metals​ ​than​ ​it​ ​does​ ​to​ ​extract
new​ ​metals​ ​from​ ​their​ ​ores
○ Mining​ ​ores​ ​is​ ​bad​ ​for​ ​the​ ​environment​ ​as​ ​large​ ​quarries​ ​are​ ​created,
which​ ​produce​ ​noise​ ​pollution​ ​and​ ​dust
○ Also,​ ​recycling​ ​allows​ ​for​ ​waste​ ​metals​ ​to​ ​be​ ​reused,​ ​saving​ ​money,
helping​ ​the​ ​environment​ ​and​ ​the​ ​supply​ ​of​ ​valuable​ ​raw​ ​materials (meaning​ ​metal​ ​ores​ ​will​ ​last​ ​longer)

Question 23

State what a Life Cycle assessment is

Answer 23

A Life Cycle Assessment measures the environmental impact of a product throughout its life. This is from obtaining the raw materials to disposal.

Question 24

What is the first stage of an LCA and what should be considered in it?

Answer 24

The first stage is extraction and processing of raw materials.

We should consider the effects of extraction.
e.g. The extraction of crude oil can cause oil spills that cause environmental damage.
The mining of metal ores can damage the environment by destroying habitats

We should consider if the raw materials are renewable or finite. e.g. plastic bags made of crude oil which is finite

Question 25

What is the second stage of an LCA and what should be considered in it?

Answer 25

The second stage is manufacture of the product and packaging.

Manufacturing may produce a large amount of electricity to run a machine or release pollutants.

Question 26

What is the third stage of an LCA and what should be considered in it?

Answer 26

Use and maintenance of the product.
When using a product, energy and water may be utilised e.g. washing machines use large amounts of energy and water.

Should consider whether a product is single or multi-use. e.g. plastic bottles are single-use because the micro plastics may get into the water supply.

Question 27

What is the fourth stage of an LCA and what should be considered in it?

Answer 27

Disposal of the product.
Possible disposal methods include recycling, incineration and landfill.
Incineration can be useful as it generates electricity but also produces carbon dioxide (a pollutant)

Question 28

What are the disadvantages of LCAs?

Answer 28

Some companies may use part of a LCA or a simplified LCA to show their product in a favourable manner.
As well, some factors are subjective or based on personal judgement like the effects of pollutants.

Question 29

What are the main things which should be considered at each stage of an LCA?

Answer 29

-The energy used
-The water used
-Pollutants released
-Transportation