Reactivity Series

Question 1

Define alloy

Answer 1

An alloy is a mixture of metal with one or more other elements

Question 2

Why are alloys stronger and harder than pure metals

Answer 2

In alloys, atoms of added element have different size from atoms in pure metal. This disrupts orderly arrangement of atoms in pure metals. It is much harder for atoms to slide over each other when force is applied

Question 3

Give the elements in the following common alloys
Mild steel
Bronze
Brass
Solder

Answer 3

Iron, carbon
Copper, tin
Copper, zinc
Tin, lead

Question 4

What is the reactivity series from most reactive to least reactive

Answer 4

Potassium, sodium, calcium, magnesium, aluminium, zinc, iron, tin, lead, hydrogen, copper, silver, gold

Question 5

Describe reaction of potassium with water

Answer 5

Potassium reacts very violently in cold water, highly exothermic. Potassium hydroxide solution and hydrogen gas produced. Potassium darts rapidly on the surface of water and melts. Fizzing occurs, hydrogen ignites instantly and metal is set on fire with sparks and lilac flame

Question 6

Describe reaction of sodium with water

Answer 6

Reacts violently in cold water. Sodium hydroxide solution and hydrogen gas produced. Sodium darts rapidly on the surface of water and melts into silvery ball. Fizzing occurs, sodium may catch fire and burn with yellow flame.

Question 7

Describe reaction of calcium with water

Answer 7

Reacts readily with cold water. Rapid effervescence seen, colourless and odourless gas evolved. Calcium hydroxide solution and hydrogen gas produced. Colourless solution turns cloudy as calcium hydroxide is only slightly soluble in water

Question 8

Describe reaction of magnesium with water

Answer 8

Magnesium reacts very slowly with cold water to form magnesium hydroxide with few bubbles of hydrogen gas produced. Hot magnesium reacts violently with steam. Magnesium oxide and hydrogen gas and hydrogen gas produced. Grey magnesium solid turns white and bright white glow is produced during reaction

Question 9

Describe reaction of aluminium with steam

Answer 9

Aluminium metal does not seem to react with water or steam. Aluminium is covered with a thin layer of non-porous aluminium oxide which adheres strongly to the metal and protects it from reacting

Question 10

Describe reaction of zinc with steam

Answer 10

Hot zinc reacts readily with steam. Zinc oxide and hydrogen gas produced. Grey zinc solid slowly becomes coated with yellow solid which becomes white when cold

Question 11

Describe reaction of iron with steam

Answer 11

Red hot iron reacts slowly with steam. Iron(II,III) oxide (Fe3O4) and hydrogen gas formed. Grey iron solid turns red hot on heating and black when cooled

Question 12

Describe reaction of calcium/magnesium with dilute hydrochloric acid

Answer 12

Reacts violently/rapidly
(Very) rapid effervescence is seen, colourless and odourless gas evolved. Colourless calcium/ magnesium chloride solution and hydrogen are formed.

Question 13

Describe reaction of aluminium with dilute hydrochloric acid

Answer 13

Aluminium does not seem to react at first as it is covered by layer of non-porous aluminium oxide which adheres strongly to the metal. Hydrochloric acid will react with aluminium oxide to form soluble aluminium chloride and water. Once oxide layer is reacted away, reaction between aluminium and acid is rapid as metal is reactive

Question 14

Describe reaction of zinc and hydrochloric acid

Answer 14

Reacts moderately fast, steady effervescence is seen, colourless and odourless gas evolved. Colourless zinc chloride solution and hydrogen are formed

Question 15

Describe reaction between iron and dilute hydrochloric acid

Answer 15

Reacts slowly. Slow effervescence is seen, colourless and odourless gas evolved. Pale green iron(II) chloride solution and hydrogen are formed.

Question 16

Describe reaction between lead and dilute hydrochloric acid

Answer 16

Reacts very slowly and reaction stops before completion. Insoluble lead(II) chloride salt formed will coat onto surface of lead metal and prevent further reaction between acid and lead metal

Question 17

Describe displacement of metals from metal salt solutions

Answer 17

Metal displacement reactions are redox reactions. A more reactive metal loses electrons more readily to form positive ions. Ions of less reactive metal will accept the electrons from more reactive metal to form metal atoms. More reactive metal will displace less reactive metal from salt solution. Further apart the two metals in reactivity series, easier/faster displacement reaction

Question 18

Describe displacement of metals from metal oxide

Answer 18

If more reactive metal is thoroughly mixed with oxide of less reactive metal and strongly heat, the more reactive metal will displace the less reactive metal from the oxide. This reaction is a thermit reaction due to a great amount of heat released

Question 19

Describe reduction of metal oxides with carbon

Answer 19

Metal oxide + carbon (heat) –> metal + CO2
More reactive metal, harder it is for carbon to take oxygen away from oxides
Oxides of metals that are above zinc in reactivity series are not reduced by carbon

Question 20

Describe reduction of metal oxides with hydrogen

Answer 20

Metal oxide + hydrogen (heat) –> metal + H2O
More reactive the metal, harder it is for hydrogen to take oxygen away from oxides
Oxides of metals above iron in reactivity series are not reduced by hydrogen

Question 21

Why must silver carbonate be stored in a cool place

Answer 21

Silver carbonate decomposes to give silver, oxygen and carbon dioxide. (Most other metal carbonates give metal oxide and carbon dioxide)

Question 22

Effect of heat on metal carbonates

Answer 22

More reactive the metal, more thermally stable is the carbonate. Metal carbonate is less easily decomposed. A greater amount of energy is required to decompose compound of more reactive metal.

Question 23

How much heating is required to heat aluminium carbonate and iron(II,III) carbonate

Answer 23

They do not exist

Question 24

How is electrolysis used to extract metals

Answer 24

Very reactive metals exist as compounds with strong chemical bonds. Electrolysis is used to break down molten ionic compounds to obtain metals. Is an expensive method to extract metals as large amount of electricity is used
K, Na, Ca, Mg, Al undergo electrolysis

Question 25

How is reduction of metal oxide using carbon used to extract metals

Answer 25

Metals are usually found as oxides or sulfides
Sulfides are heated in air to form oxides.
Oxides are heated with carbon to obtain metal
Zn, Fe, Sn, Pb, Cu, Ag undergo reduction

Question 26

How to extract gold and platinum

Answer 26

Gold and platinum are unreactive and found naturally uncombined in ground as elements

Question 27

What is rusting

Answer 27

Rusting is slow oxidation of iron to form hydrated iron(III) oxide. Rust is reddish-brown substance that forms on surface of object made of iron when object is exposed to air and moisture.

Question 28

What are conditions for rusting

Answer 28

Water and oxygen, presence of sodium chloride and acid substances also speed up rusting process

Question 29

Why do substances rust once protective layer is removed

Answer 29

If an object plated with tin is scratched, water and oxygen can reach iron. Iron, being more reactive than tin, loses electrons more readily than tin. Iron will corrode quickly

Question 30

What metal is used in galvanisation

Answer 30

ZINC

Question 31

Why does an iron object with a block of zinc attached not rust

Answer 31

Zinc is more reactive than iron and loses electrons more readily than iron, zinc corrodes in place of iron as sacrificial protection

Question 32

What are the three ways to prevent rusting

Answer 32

Using sacrificial metal, protective layer or rust resistant alloy