11: Reactivity of Metals

Question 1

List 4 parameters to compare the reactivity of metals.

Answer 1

1. formation rate of products
2. consumption rate of reactants
3. reacting temperature
4. amount of energy change during the reaction

Question 2

List 3 metals that react with cold water in decreasing order of reactivity.

Answer 2

potassium, sodium, calcium

Question 3

List 5 metals that react with steam but not with cold water in decreasing order of reactivity.

Answer 3

magnesium, aluminium, zinc, iron, tin

Question 4

List a metal that reacts with dilute acid but not with steam.

Answer 4

lead

Question 5

List 2 metals that react with oxygen in air but not with dilute acid in decreasing reactivity.

Answer 5

copper, mercury

Question 6

What is the word equation for metals’ reaction with oxygen?

Answer 6

metal + oxygen -> metal oxide

Question 7

What is the word equation for metals’ reaction with liquid water?

Answer 7

metal + water -> metal hydroxide + hydrogen gas

Question 8

What is the word equation for metals’ reaction with steam?

Answer 8

metal + water(g) -> metal oxide + hydrogen gas

Question 9

What is the word equation for metals’ reaction with dilute acid?

Answer 9

metal + dilute acid -> metal salt + hydrogen gas

Question 10

What is the balanced chemical equation for sodium’s reaction with oxygen?

Answer 10

4Na + O₂ -> 2Na₂O

Question 11

What is the balanced chemical equation for postassium’s reaction with oxygen?

Answer 11

4K + O₂ -> 2K₂O

Question 12

What is the balanced chemical equation for alkali metals’ reactions with oxygen?

Answer 12

4M + O₂ -> 2M₂O

Question 13

What is the balanced chemical equation for calcium’s reaction with oxygen?

Answer 13

2Ca + O₂ -> 2CaO

Question 14

What is the balanced chemical equation for magnesium’s reaction with oxygen?

Answer 14

2Mg + O₂ -> 2MgO

Question 15

What is the balanced chemical equation for alkaline earth metals’ reactions with oxygen?

Answer 15

2M + O₂ -> 2MO

Question 16

What is the balanced chemical equation for aluminium’s reaction with oxygen?

Answer 16

4Al + 3O₂ -> 2Al₂O₃

Question 17

What is the balanced chemical equation for zinc’s reaction with oxygen?

Answer 17

2Zn + O₂ -> 2ZnO

Question 18

What is the balanced chemical equation for iron’s reaction with oxygen?

Answer 18

3Fe + 2O₂ -> FeO * Fe₂O₃

Question 19

What is the word equation for iron’s reaction with oxygen?

Answer 19

iron + oxygen -> iron(II, III) oxide

Question 20

What is the balanced chemical equation for lead’s reaction with oxygen?

Answer 20

2Pb + O₂ -> 2PbO

Question 21

What is the balanced chemical equation for copper’s reaction with oxygen?

Answer 21

2Cu + O₂ -> 2CuO

Question 22

Do aluminium compounds have a flame colour?

Answer 22

No, they have no particular colour. The reason they burn with a bright white light is becasue the reaction between aluminium and oxygen gives out a lot of energy.

Question 23

Do magnesium compounds have a flame colour?

Answer 23

No, they have no particular colour. The reason they burn with a bright white light is becasue the reaction between magnesium and oxygen gives out a lot of energy.

Question 24

What is the balanced chemical equation for sodium’s reaction with liquid water?

Answer 24

2Na + 2H₂O -> 2NaOH + H₂

Question 25

What is the balanced chemical equation for potassium's reaction with liquid water?

Answer 25

2K + 2H₂O -> 2KOH + H₂

Question 26

What is the balanced chemical equation for alkali metals' reactions with liquid water?

Answer 26

2M + 2H₂O -> 2MOH + H₂

Question 27

What is the balanced chemical equation for calcium's reaction with liquid water?

Answer 27

Ca + **2**H₂O -> **Ca(OH)₂** + 2H₂

Question 28

What is the balanced chemical equation for calcium's reaction with steam?

Answer 28

Ca + H₂O -> **CaO** + 2H₂

Question 29

What is the balanced chemical equation for magnesium's reaction with steam?

Answer 29

Mg + H₂O -> MgO + H₂

Question 30

What is the balanced chemical equation for aluminium's reaction with steam?

Answer 30

2Al + 3H₂O -> AL₂O₃ + 3H₂

Question 31

Why do metals form oxides when reacted with steam and hydroxides when reacted with water?

Answer 31

In steam, the water molecules are packed less closely together. One metal atom is less likely to react with two water molecules to form metal hydroxides than to form metal oxides.

Question 32

List 5 metals that react with steam but not cold water in decreasing order of reactivity.

Answer 32

magnesium, aluminium, zinc, iron, tin

Question 33

List 6 metals that react with do not react with water nor steam in decreasing order of reactivity.

Answer 33

lead, copper, mercury, silver, platinum, gold

Question 34

What is the balanced chemical equation for alkali metals' reactions with dilute hydrochloric acid?

Answer 34

2M + 2HCl -> 2MCl + H₂

Question 35

What is the balanced chemical equation for alkali metals' reactions with dilute sulphuric acid?

Answer 35

2M + H₂SO₄ -> M₂SO₄ + H₂

Question 36

What is the balanced chemical equation for alkali metals' reactions with dilute nitric acid?

Answer 36

2M + 2HNO₃ -> 2MNO₃ + H₂

Question 37

What is the balanced chemical equation for alkaline earth metals' reactions with dilute hydrochloric acid?

Answer 37

M + 2HCl -> MCl₂ + H₂

Question 38

What is the balanced chemical equation for alkaline earth metals' reactions with dilute sulphuric acid?

Answer 38

M + H₂SO₄ -> MSO₄ + H₂

Question 39

What is the balanced chemical equation for alkaline earth metals' reactions with dilute nitric acid?

Answer 39

M + 2HNO₃ -> M(NO₃)₂ + H₂

Question 40

What is the balanced chemical equation for lead's reaction with dilute nitric acid?

Answer 40

Pb + 2HNO₃ -> Pb(NO₃)₂ + H₂

Question 41

What is the balanced chemical equation for iron's reaction with dilute sulphuric acid?

Answer 41

Fe + H₂SO₄ -> FeSO₄ + H₂

Question 42

What is the word equation for iron's reaction with dilute sulphuric acid?

Answer 42

iron + dilute sulphuric acid -> **iron(II)** sulphate + hydrogen

Question 43

List 2 metals that react with dilute hydrochloric acid explosively in decreasing order of reactivity.

Answer 43

potassium, sodium

Question 44

List 5 metals that do not react with dilute hydrochloric acid in decreasing order of reactivity.

Answer 44

copper, mercury, silver, platinum, gold

Question 45

What is the meaning of a double arrow in chemical equations?

Answer 45

The reaction is **reversible**.

Question 46

What is the definition of reactivity of metals?

Answer 46

The most reactive metal is the one that has **the highest tendency to lose the outermost shell electron(s)** to form a positive ion.

Question 47

Why are alkali metals more reactive than alkaline earth metals in the same period?

Answer 47

Alkali metals lose one electron to form ions, while alkaline earth metals lose 2. Losing one electron is easier than losing 2 electrons. This is because once an electron is removed from an atom, a **positive ion** is created and it **attracts a negatively charged ion more strongly than a neutral atom**. Therefore, more energy is required to remove the second electron and so on.

Question 48

Why are metals from lower periods more reactive than those from upper periods from the same group?

Answer 48

**shielding effect**: as the number of protons increases, the attraction force between nucleus and electrons increases. However, the inner shell electrons exert **more repulsion** to the outermost electrons. The increase in shielding effect **outweighs the increase in nuclear charge**, so it is overall easier for metals to lose electrons down the group. Therefore, metals are more reactive down the group.

Question 49

What is a displacement reaction?

Answer 49

In a displacement reaction, a **more reactive metal** displaces a **less reactive metal** from its compound in a solution.

Question 50

List 2 observations when a piece of copper is added to silver nitrate solution.

Answer 50

1. A grey solid is deposited on the copper. 2. The solution turns from colourless to blue.

Question 51

What is the definition of spectator ions?

Answer 51

Spectator ions are ions that do not change their physical state nor chemical nature in a chemical reaction.

Question 52

What is the ionic equation of silver nitrate's reaction with sodium chloride?

Answer 52

1. **balanced chemical equation with physical states**: AgNO₃(aq) + NaCl(aq) -> AgCl(s) + NaNO₃(aq) 2. **rewriting aqueous compounds as ions**: Ag⁺(aq) + NO₃^-(aq) + Na⁺(aq) + Cl^-(aq) -> AgCl(s) + Na⁺(aq) + NO₃^-(aq) 3. **deleting spectator ions**: the ionic equation is Ag⁺(aq) + Cl^-(aq) -> AgCl(s)

Question 53

What is the ionic equation of sodium hydroxide's reaction with hydrochloric acid?

Answer 53

1. **balanced chemical equation with physical states**: NaOH(aq) + HCl(aq) -> NaCl(aq) + H₂O(l) 2. **rewriting aqueous compounds as ions**: Na⁺(aq) + OH^-(aq) + H⁺(aq) + Cl^-(aq) -> Na⁺(aq) + Cl^-(aq) + H₂O(l) 3. **deleting spectator ions**: the ionic equation is H⁺(aq) + OH^-(aq) -> H₂O(l)

Question 54

What is the relationship between the reactivity and the ease of extraction of a metal?

Answer 54

The more reactive a metal is, the more difficult it is the be extracted from its ore.

Question 55

What is the relationship between the reactivity of a metal and the stability of its compounds?

Answer 55

The more reactive a metal is, the more stable its compounds are likely to be. (example: the less reactive a metal is, the more readily its oxide decomposes when heated.)

Question 56

What is the definition of thermit reaction?

Answer 56

Thermit reactions are **exothermic** reactions between a **metal powder** and a **metal oxide**.