Reactivity of Metals

Question 1

What is the equation for a reaction between a metal and water?

Answer 1

Metal + water → Metal hydroxide + hydrogen

Question 2

What is the order of reactivity? Describe their reactions with water and acid

Answer 2

Potassium - reacts quickly with cold water - vigorous reaction with acid
Sodium - reacts quickly with cold water - vigorous reaction with acid
Calcium - reacts quickly with cold water - vigorous reaction with acid
Magnesium - very slow reaction with water - reaction becoming less vigorous
Aluminium - none - reaction becoming less vigorous
Zinc - reacts with steam - reaction becoming less vigorous
Carbon (not a metal)
Iron - reacts with steam - reaction becoming less vigorous
Tin
Lead
Hydrogen
Copper - no reaction with water - no reaction with acid
Silver - no reaction with water - no reaction with acid
Gold - no reaction with water - no reaction with acid
Platinum - no reaction with water - no reaction with acid

Question 3

Why does aluminium not react with water?

Answer 3

It has a layer of aluminium oxide which stops the water from reacting with the metal below

Question 4

Why does calcium not react as quickly with sulfuric acid?

Answer 4

A layer of insoluble calcium sulfate forms which slows down the reaction

Question 5

Why does magnesium react very slowly with water?

Answer 5

A sparingly soluble layer of magnesium hydroxide forms which slows the reaction

Question 6

How does displacement work?

Answer 6

A more reactive metal displaces another metal from a metal compound, this means that the more reactive metal is now part of the compound and the less reactive metal is on it’s own as an element

Question 7

What is an ore?

Answer 7

A rock that contains enough metal to make the extraction of the metal economical

Question 8

What is a low-grade ore?

Answer 8

A rock that contains too little metal to make the extraction worthwhile

Question 9

What form are unreactive metals found in in the earth’s crust?

Answer 9

Their native state (uncombined with other metals) however they may naturally occur as alloys (mixtures of metals)

Question 10

What is the trend in how easily a metal corrodes in terms of reactivity?

Answer 10

The less reactive a metal is the slower it corrodes, until it gets to gold and below which don’t corrode

Question 11

How are metals that are more reactive than carbon extracted?

Answer 11

Using electrolysis of the molten compound

Question 12

How are metals less reactive than carbon extracted?

Answer 12

Using reduction of its oxide using carbon

Question 13

What is the example reaction of oxidation using carbon?

Answer 13

Metal compound + carbon → Metal + carbon compound

Question 14

Why do metals such as silver and gold not need to extracted?

Answer 14

They are naturally found as the element

Question 15

How can copper be extracted other than using reduction with carbon?

Answer 15

Using displacement with scrap iron, iron is more reactive than copper so it can displace it from a compound

Question 16

What is phytoextraction?

Answer 16

Biological method of extraction that uses plants, it extracts metal compounds from the ground

Question 17

How does phytoextraction work?

Answer 17

• Metal compounds is absorbed by roots of a plant
• Plant concentrates metal compounds in its shoots and roots
• The plant is then burned
• The ash contains metal compounds

Question 18

What is bioleaching?

Answer 18

Biological method of metal extraction using bacteria

Question 19

How does bioleaching of copper sulfide work?

Answer 19

• Sulfide ions (S2-) are oxidised by the bacteria
• Copper sulfide ores break down
• Cu2+ ions are released
• A leachate is produced containing a high concentration of copper ions
• Copper can be obtained from the leachate using scrap iron

Question 20

What are the key facts about low-grade ores?

Answer 20

• They’re more common that high-grade ores
• They’re less profitable
• Take more energy to extract
• Produce more waste

Question 21

What are the advantages of recycling metals?

Answer 21

• Metal ores will last longer
• Less energy is needed than extraction
• Fewer quarries are needed
• Less noise and dust is produced

Question 22

What are the disadvantages of recycling metals?

Answer 22

• Used metal items must be collected and transported to the recycling centre
• Different metals must be removed from used items and sorted
• Recycling won’t always save a lot of energy as it depends on the metal involved

Question 23

What are the basic stages of a life-cycle assessment?

Answer 23

• Raw materials are obtained
• These materials are manufactured into the product
• The product is used
• The product is disposed of