Extracting Metals And Equilibria

Question 1

What is oxidation in terms of oxygen?

Answer 1

Oxidation is the gain of oxygen by a substance.

Question 2

What is reduction in terms of oxygen?

Answer 2

Reduction is the loss of oxygen from a substance.

Question 3

What is oxidation in terms of electrons?

Answer 3

Oxidation is the loss of electrons.

Question 4

What is reduction in terms of electrons?

Answer 4

Reduction is the gain of electrons.

Question 5

What is a redox reaction?

Answer 5

A reaction where both oxidation and reduction occur simultaneously.

Question 6

What is a displacement reaction?

Answer 6

A reaction where a more reactive metal displaces a less reactive metal from its compound.

Question 7

How are displacement reactions examples of redox reactions?

Answer 7

Because the more reactive metal is oxidized (loses electrons), and the less reactive metal is reduced (gains electrons).

Question 8

How can the reactivity of metals be determined?

Answer 8

By observing their reactions with water, acids, and salt solutions.

Question 9

What is the reactivity series?

Answer 9

A list of metals (and some non-metals) ordered by their ability to form positive ions.

Question 10

How does the reactivity of a metal relate to its ability to form positive ions?

Answer 10

The more reactive a metal is, the more readily it forms positive ions.

Question 11

How does a metal’s resistance to oxidation relate to its position in the reactivity series?

Answer 11

Metals lower in the reactivity series are more resistant to oxidation.

Question 12

What is the general reaction of metals with dilute acids?

Answer 12

Metal + Acid → Salt + Hydrogen gas

Question 13

What is the general reaction of certain metals with water?

Answer 13

Metal + Water → Metal hydroxide + Hydrogen gas

Question 14

How can the order of reactivity of metals be determined using their reactions?

Answer 14

By comparing their reactions with acids, water, and salt solutions.

Question 15

What is an ore?

Answer 15

A rock that contains enough of a metal compound to make it economically worthwhile extracting the metal.

Question 16

How are unreactive metals found in the Earth’s crust?

Answer 16

As uncombined elements.

Question 17

How are most metals found in the Earth’s crust?

Answer 17

As compounds, often oxides.

Question 18

How can metals less reactive than carbon be extracted from their ores?

Answer 18

By reduction with carbon.

Question 19

Why is electrolysis used to extract certain metals?

Answer 19

Because metals more reactive than carbon cannot be extracted by reduction with carbon.

Question 20

Why is extracting metals using carbon cheaper than using electrolysis?

Answer 20

Because electrolysis requires more energy and expensive equipment.

Question 21

How is aluminium extracted from its ore?

Answer 21

By electrolysis of aluminium oxide dissolved in molten cryolite.

Question 22

Why is aluminium oxide dissolved in molten cryolite before electrolysis?

Answer 22

To lower the melting point, reducing energy costs.

Question 23

What forms at the negative electrode during the electrolysis of aluminium oxide?

Answer 23

Aluminium metal.

Question 24

What forms at the positive electrode during the electrolysis of aluminium oxide?

Answer 24

Oxygen gas.

Question 25

What happens to the oxygen produced at the positive electrode during aluminium extraction?

Answer 25

It reacts with the carbon electrodes to form carbon dioxide.

Question 26

Why are alternative methods of metal extraction being developed?

Answer 26

Because supplies of metal-rich ores are limited and traditional methods are environmentally damaging.

Question 27

What is bioleaching?

Answer 27

Using bacteria to extract metals from low-grade ores.

Question 28

What is phytomining?

Answer 28

Using plants to absorb metal compounds from the soil, then burning the plants to obtain the metals.

Question 29

What are the advantages of recycling metals?

Answer 29

• Conserves finite resources • Reduces environmental impact • Saves energy compared to extracting new metals

Question 30

What is a life cycle assessment (LCA)?

Answer 30

An evaluation of the environmental impact of a product throughout its life: from raw material extraction, manufacturing, use, to disposal.

Question 31

What stages are considered in a life cycle assessment?

Answer 31

• Obtaining raw materials • Manufacturing • Using the product • Disposing of the product

Question 32

(Six Marker) Describe how to determine the relative reactivity of metals using their reactions.

Answer 32

• React metals with water, acids, and salt solutions • Observe the rate and vigor of reactions • More reactive metals will react more vigorously and rapidly • Record observations such as gas production, temperature change, and displacement • Rank metals based on their reactivity in these reactions • Use this information to construct a reactivity series

Question 33

(Six Marker) Explain the process of extracting aluminium from its ore.

Answer 33

• Aluminium is extracted from bauxite, which contains aluminium oxide • Aluminium oxide is dissolved in molten cryolite to lower the melting point • Electrolysis is used: • At the cathode (negative electrode), aluminium ions gain electrons to form aluminium metal • At the anode (positive electrode), oxide ions lose electrons to form oxygen gas • Oxygen reacts with the carbon anodes, producing carbon dioxide • The aluminium metal is collected at the bottom of the electrolysis cell

Question 34

(Six Marker) Evaluate the advantages and disadvantages of bioleaching and phytomining.

Answer 34

Advantages: • Can extract metals from low-grade ores • Less energy-intensive than traditional methods • Reduces environmental impact of mining Disadvantages: • Slower process • May produce toxic by-products • Requires careful management to prevent environmental damage