Topic 4 - Extracting Metals And Equilibria

Question 1

What are the products when a metal reacts with cold water?

Answer 1

Metal hydroxide and hydrogen gas

Question 2

What are the products when a metal reacts with steam?

Answer 2

Metal oxide and hydrogen gas

Question 3

Write the chemical equation for the reaction that occurs when calcium reacts with cold water

Answer 3

Ca + 2H₂O -> Ca(OH)₂ + H₂

Question 4

Write the chemical equation for the reaction that occurs when zinc reacts with steam

Answer 4

An + H ₂ O -> ZnO + H ₂

Question 5

What are the products when a metal reacts with dilute acid?

Answer 5

Salt + hydrogen

Question 6

If a metal reacts with cold water, what does it suggest about the reactivity of this metal?

Answer 6

Metal is very reactive as only most reactive metals can react with cold water

Question 7

A metal reacts with oxygen but not acid or cold water. What does this suggest about the reactivity of this metal?

Answer 7

Not very reactive, most metals react with oxygen

Question 8

Name a metal which will not react with water, acid or oxygen

Answer 8

Gold

Question 9

Describe an experiment that uses displacement to compare reactivity of 2 metals

Answer 9

Add solid to salt solution (contains metal)

If solid metal = more reactive will gradually disappear, displacing the metal in salt solution

Question 10

What would you expect to observe when magnesium is added to copper sulfate solution?

Answer 10

Copper sulfate solution = blue

Mg = more reactive than copper so when magnesium is added, blue solution decolourises and copper coats surface of Mg.

Question 11

Why can a displacement reaction be called a redox reaction? (In terms of electrons)

Answer 11

More reactive metal atoms lose electrons to form ions (oxidation)
Less reactive metal ions gain electrons to form element (reduction)

Question 12

The reactivity of a metal is related to its tendency to form …

Answer 12

Cations (positive ions)

Question 13

Which metals are most easily oxidised?

Answer 13

Metals highest in reactivity series

Question 14

Which metals are more likely to react with water and dilute acids to form cations?

Answer 14

More reactive metals

Question 15

Where are most metals extracted from?

Answer 15

Ores found in earths crust

Question 16

What is an ore?

Answer 16

A rock containing metals often chemically combined with other substances

Question 17

Which metals are found in the earths crust as uncombined elements?

Answer 17

Unreactive metals

Question 18

Explain what oxidation means in terms of oxygen

Answer 18

Gain of oxygen

Question 19

Explain what reduction means in terms of oxygen

Answer 19

Loss of oxygen

Question 20

Most ores contain metals chemically combined with oxygen. What process must be carried out to extract the metal?

Answer 20

Reduction

Question 21

Which 2 methods could be used to extract metals from their ores?

Answer 21

Reduction with carbon- only if metal = less reactive than carbon

Electrolysis- lots of energy (high cost)

Question 22

How would you extract iron from its ore?

Answer 22

Reduction with carbon

Electrolysis

Question 23

Chemical equation for reduction of iron with carbon

Answer 23

2Fe₂O₃ + 3C -> 4Fe + 3CO ₂

Question 24

How can aluminium be extracted from its ore?

Answer 24

Electrolysis (is more reactive than carbon)

- when molten ore undergoes electrolysis, metal forms at cathode

Question 25

When aluminium is extracted from aluminium oxide, why is it first dissolved in molten cryolite?

Answer 25

Aluminium oxide has very high melting pt. Dissolved to produce electrolyte with lower melting pt- reduce energy and cost

Question 26

How can plants be used as an alternative metal extraction method?

Answer 26

Phytoextraction:

• Plants grown in areas with metals in soil.
• Take up metals through roots and concentrate them in shoots and leaves.
• Plamts burned and metal removed from ash

Question 27

How can bacteria be used as an alternative metal extraction method?

Answer 27

Bacterial extraction:

• Bacteria absorbs metal compounds
• Produce solutions called leachates containing metals
• Scrap iron used to remove metal from leachate

Question 28

Limitations of biological methods of extraction?

Answer 28

Only suitable for low grade ores with lower quantities of metals.
Slow process.
Require displacement or electrolysis for final step.

Question 29

How is a metals relative resistance to oxidation related to its position in the reactivity series?

Answer 29

Metals lower in reactivity series are less reactive so less likely to form cations - more resistant to oxidation

Question 30

Advantages of recycling metals?

Answer 30

Economically beneficial (electrolysis=expensive)
Prevents detrimental environmental impact of mining and extraction of new metals
Less waste produced = less landfill
Less energy required for electrolysis
More sustainable
Provides employmemt

Question 31

What is a life cycle assessment?

Answer 31

Analysis of overall environmental impact that a product may have throughout its lifetime

Question 32

What different factors does a life cycle assessment of a product consider?

Answer 32

Extraction and processing of raw materials
Manufacturing
Packaging and transportation
Use of product
Disposal