Extracting Metals And Equilibra

Question 1

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

Answer 1

Metal hydroxide and hydrogen gas

Question 2

What are 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

Zn + H20 —> ZnO + H2

Question 5

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

Answer 5

Salt and hydrogen

Question 6

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

Answer 6

It suggest that metal is very reactive as only the 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 the reactivity of two metals

Answer 9

Add a solid metal to a salt solution (the Salt must contain a different metal)

If the solid metal is more reactive, it will gradually disappear, displacing the metal that was in the salt solution.

If nothing happens, the metal in the salt is more reactive and can’t be displaced.

Question 10

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

Answer 10

Copper sulfate is blue. Magnesium is more reactive than copper so when magnesium is added the blue solution decolourises and copper coats the surface of the magnesium.

Question 11

Why can a displacement reaction be called a redox reaction. Explain in terms of electron transfer

Answer 11

A redox reaction occurs when reduction and oxidation are taking place in the same reaction.

In a displacement reaction, the more reactive metal atoms loses electrons to form ions (oxidation) and the less reactive metals ions gains electrons to form the element (reduction)

Question 12

What is the reactivity of a metal?

Answer 12

It is the tendency of the a metal to form cations (positive ions)

Question 13

Why can displacement reaction be called a redox reaction. Explain in terms of electron transfer

Answer 13

A redox reaction occurs when reduction and oxidation are taking place in same reaction.

In a displacement reaction, the more reactive metal atoms lose electrons to form ions (oxidation) and the less reactive metal ions gain electrons to form the element (reduction).

Question 14

What is the reactivity of a metal?

Answer 14

It is the tendency of a metal to form cations

Question 15

Which metals are most easily oxidised?

Answer 15

The metals highest in the reactivity series. More reactive metals are more likely to react with water and dilute acids to form cations.

Question 16

Where are most metals extracted from?

Answer 16

From ores found in the Earth’s crust

Question 17

What is an ore?

Answer 17

A rock which contains metals often chemically combined with other substances.

Question 18

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

Answer 18

Gold,silver, platinum - unreactive metals

Question 19

Explain what oxidation means in terms of oxygen

Answer 19

Gain of oxygen

Question 20

Explain what reduction means in terms of oxygen.

Answer 20

Loss of oxygen

Question 21

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

Answer 21

Reduction

Question 22

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

Answer 22

Reduction with carbon: can only be done if the metal is less reactive than carbon (links to reactivity series)

Electrolysis: can be done with all metals, but requires a large amount of energy (high cost)

Question 23

How would you extract iron from its ore?

Answer 23

Iron is less reactive than carbon so can be extracted by reduction with carbon.
Electrolysis could be used, but this would use a lot unnecessary energy (high cost).

Question 24

What’s the chemical equation for reduction of iron with carbon?

Answer 24

Question 25

How can aluminium be extracted from its ore?

Answer 25

Aluminium is more reactive than carbon so electrolysis must be used. When molten ore undergoes electrolysis the metal forms at the cathode.

Question 26

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

Answer 26

Aluminium oxide has a very high melting point. It is dissolved in molten cryolite to produce an electrolyte with a lower melting point, reducing energy usage and cost.

Question 27

How can plants be used as an alternative extraction method? How does it work?

Answer 27

Phytoextraction: Plants are grown in areas with metals in the soil. The plants take up metals through their roots and concentrate them in their shoots and leaves. These plants are burned and the metals extracted from the ash.

Question 28

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

Answer 28

Bacterial extraction: Some bacteria absorb metal compounds. These bacteria produce solutions called leachates containing the metals. Scrap iron can be used to remove the metal from the leachate.

Question 29

What are limitations of biological methods of extraction?

Answer 29

Only suitable for low grade ores with smaller quantities of metals. Slow processes Requires displacement or electrolysis for the final step.

Question 30

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

Answer 30

Oxidation is the loss of electrons. Metals lower in the reactivity series are less reactive. This means they are less likely to form their cations so are more resistant to oxidation.

Question 31

What are advantages of recycling metals?

Answer 31

Economically beneficial because electrolysis is expensive Prevents the detrimental environment impact of mining and extraction of new metals. Less energy required compared to electrolysis More sustainable- not using finite resources Recycling process provides employment.

Question 32

What is a life cycle assessment?

Answer 32

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

Question 33

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

Answer 33

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

Question 34

What is reversible reaction?

Answer 34

A reaction in which the products can reaction to form the original reactants

Question 35

How can direction of a reversible reaction be altered?

Answer 35

Changing reaction conditions | Temperature, pressure, concentration

Question 36

What is meant by dynamic equilibrium?

Answer 36

Dynamic equilibrium is when the rate of the forward reaction equals the rate of the backwards reaction. This means the concentration of reactants and products are constants even though compounds are continually reacting.

Question 37

What is a closed system?

Answer 37

A system where nothing is added or removed. All reactants and products remain in the reaction vessel.

Question 38

Why is equilibrium only reached if the reaction takes place in a closed system?

Answer 38

The closed system prevents any reactants and products escaping so that they are able to react continuously.

Question 39

What haber process?

Answer 39

Industrial process for making ammonia(used in fertilisers)

Question 40

Write the chemical equation for reversible between nitrogen and hydrogen, forming ammonia?

Answer 40

Question 41

Where the sources of nitrogen and hydrogen for the haber process?

Answer 41

Nitrogen: extracted from the air Hydrogen: obtained from natural gas

Question 42

What conditions are used for the haber process?

Answer 42

450°C 200 atm pressure Iron catalyst

Question 43

Explain the effect of changing the temperature of a reversible reaction if the forward reaction is endothermic

Answer 43

The forward reaction is endothermic so increasing temperature favours the forward reaction (system tries to reverse the change). The equilibrium will shift towards the forward reaction and the yield of the products will increase.

Question 44

Explain the effect of changing the pressure of a reversible gaseous reaction.

Answer 44

An increase in pressure will favour the reaction that produces the least number of molecules. The equilibrium position will shift towards the side that produces the fewest gaseous molecules.

Question 45

Answer 45

Increasing the pressure will shift equilibrium to the right as there are fewer molecules of gas. The yield of ammonia will increase.

Question 46

The concentration of the reactants are increased during a reversible reaction. What effect will this have on equilibrium position?

Answer 46

The equilibrium will shift to the right so that product yield will increase. This will reduce the effect of increased concentration of the reactants.

Question 47

If there are equal gaseous molecules on either side of a reaction, what effect will changing the pressure have on the equilibrium position?

Answer 47

No effect.

Question 48

Recall the reactivity series: and what reacts with water(cold) and dilute acid.

Answer 48