Obtaining and using metals

Question 1

properties of more reactive metals: (2)

Answer 1

-more vigorous reactions
-easily loses electrons in reactions to form positive ions (cations)

Question 2

what is formed when a metal reacts with water?

Answer 2

Metal + water → metal hydroxide + hydrogen

Question 3

what is formed when a metal reacts with steam?

-how does it usually react with cold water?

Answer 3

Metal + steam → metal oxide + hydrogen

-metals that react slowly with cold water can react quickly with steam

Question 4

what will a metal below hydrogen on the reactivity series NOT do?

Answer 4

react with dilute acids.

Question 5

what happens in the reactions of metals with water, steam and acids? (2)

Answer 5

-metals lose electrons and form cations.
-metal is oxidised and the water is reduced.

Question 6

how can you predict a metal’s relative tendency to form cations and its resistance to oxidation? (2)

Answer 6

the higher up a metal, the greater the tendency to form cations
the lower down a metal, the greater its resistance to oxidation

Question 7

how does displacement occur in solutions?

Answer 7

a more reactive metal can displace a less reactive metal from its compounds.

Question 8

how can a reactivity series be deduced? (3)

Answer 8

-by carrying out several displacement reactions.
-piece of metal is dipped into a salt solution.
-different combinations of metal and salt solution are tested

Question 9

Explain why three combinations of metal and salt solution were not done in the investigation? (for deducing reactivity) (2)

Answer 9

-a metal cannot displace itself from a solution of one of its salts.
-there would be no reaction (so these combinations were not done)

Question 10

what are redox reactions?

Answer 10

when reduction and oxidation happen at the same time,

Question 11

what is an ore?

Answer 11

a rock that contains a metal or a metal compound

Question 12

difference between low-grade and high-grade ores: (2)

Answer 12

-low-grade ores contain a small percentage of the metal or its compound
-high-grade ores contain a larger percentage

Question 13

why is it wasteful to extract metal from low-grade ores?

Answer 13

expensive for a small amount of metal

Question 14

how are metals extracted if they are LESS reactive or MORE reactive then carbon? (2)

Answer 14

less reactive than carbon:
-it can be extracted from its compounds by heating with carbon.

more reactive than carbon:
-electrolysis

Question 15

what is formed when a metal oxide reacts with carbon?

Answer 15

Metal oxide + carbon → metal + carbon dioxide

Question 16

how and why can be extract iron? (3)

Answer 16

-below carbon in the reactivity series it can be displaced from its compounds by heating with carbon.
-iron is extracted from iron ore in a large container called a blast furnace.
-iron(III) oxide is reduced to molten iron when it reacts with carbon

Question 17

why is aluminium more expensive than carbon even though it is ore abundant in the Earth’s crust?

Answer 17

large amounts of electrical energy used in the extraction process.

Question 18

why does aluminium need to be molten in order to be extracted? (3)

-what problem could arise from this?

Answer 18

-aluminium oxide is insoluble in water, so it must be molten to act as an electrolyte.
-melting point of aluminium oxide is high.
-lots of energy must be transferred to break its strong ionic bonds = expensive

Question 19

how could we reduce the costs from melting aluminium oxide? (2)

Answer 19

-powdered aluminium oxide is dissolved in molten cryolite.
-this ionic compound melts at a lower temperature than aluminium oxide, reducing costs.

Question 20

what happens during the electrolysis of aluminium oxide? (2)

Answer 20

-cathode = aluminium ions gain electrons and form aluminium atoms
-anode = oxide ions lose electrons and form oxygen gas

Question 21

why must the electrodes used in separating aluminium oxide be changed? (3)

Answer 21

-oxygen reacts with the carbon anodes, forming carbon dioxide.
-the anodes gradually wear away and must be replaced frequently,
-adding to the cost of producing aluminium

Question 22

Explain, with the help of a half equation, how oxide ions are oxidised during the electrolysis of aluminium oxide.

Answer 22

2O⁻² - 4e-. → O₂

Question 23

Explain, with the help of a half equation, how aluminium ions are reduced during the electrolysis of aluminium oxide.

Answer 23

Al³⁺ + 3e- → Al

Question 24

what does recycling a metal involve?

Answer 24

collecting used metal items and producing new metal from them.

Question 25

describe the steps involved in recycling a metal: (3)

Answer 25

-collecting and transporting the used items to a recycling centre
-breaking up and sorting the different metals
-removing impurities from the metals

Question 26

advantages of recycling compared to producing metals from metal ore: (3)

Answer 26

-more economic - less energy is needed to produce a metal
-less damage to the environment - fewer quarries and mines, less noise and less heavy traffic
-saves valuable raw materials - reserves of metal ores will last longer

Question 27

explain recycling aluminium saves more energy than recycling iron: (3)

Answer 27

-aluminium is extracted from its ore using electrolysis but iron is extracted by heating with carbon.
-electrolysis uses more energy, so more energy is used to extract aluminium in the first place.
-aluminium has a lower melting point than iron, so less energy is needed to melt it during recycling.

Question 28

describe the disadvantages of recycling: (2)

Answer 28

-the collection and transport of used items needs organisation, workers, vehicles and fuel
-it can be difficult to sort different materials from one another

Question 29

Describe a simple way to separate aluminium from iron.

Answer 29

A magnet or electromagnet will attract iron but not aluminium.

Question 30

what is a life-cycle assessent?

Answer 30

analysis of the impact of a manufactured product on the environment