4: Period 3

Question 1

Suggest why sodium oxide forms a solution with a higher pH than the solution formed from magnesium oxide.

Answer 1

The oxide ions react with water to form OH- alkaline ions. NaOH is more soluble than Mg(OH)2

Question 1

Phosphorus burns in air to form phosphorus oxide. Give an equation.

Answer 1

4P + 5O2 -> P4O10

Question 2

Give an equation for the reaction between phosphorus oxide and water.

Answer 2

P4O10 + 6H2O -> 4H3PO4

Question 3

Give 2 equations to show how vanadium(V) oxide acts as a catalyst in the contact process.

Answer 3

V2O5 + SO2 → V2O4 + SO3
V2O4 + 0.5O2 → V2O5

Question 4

Give an equation for the reaction of sodium with water.

Answer 4

2Na + 2H2O -> 2NaOH + H2

Question 5

Why is sodium more reactive than magnesium?

Answer 5

It takes less energy to lose one outer electron than 2.

Question 6

Describe the reaction with sodium and water.

Answer 6

Vigorous

Question 7

Give an equation for the reaction with magnesium and water.

Answer 7

Mg + 2H2O -> Mg(OH)2 + H2

Question 8

Give an equation for the reaction of Mg with Steam.

Answer 8

Mg + H2O (g) -> MgO + H2

Question 9

Give an equation for the reaction of Na with O2.

Answer 9

2Na + 0.5O2 -> Na2O

Question 10

Give an equation for the reaction of Mg with O2.

Answer 10

Mg + 0.5O2 -> MgO

Question 11

Give an equation for the reaction of Al with O2.

Answer 11

2Al + 1.5O2 -> Al2O3

Question 12

Give an equation for the reaction of Si with O2.

Answer 12

Si + O2 -> SiO2

Question 13

Give an equation for reaction of P with O2.

Answer 13

P4 + 5O2 -> P4O10

Question 14

Give an equation for the reaction of S with O2.

Answer 14

S + O2 -> SO2

Question 15

Give the oxidation state of S in SO2.

Answer 15

+4

Question 16

Give the conditions needed to form SO3.
Give the oxidation state of S in SO3.

Answer 16

High temperature and catalyst.
Oxidation state of S is +6

Question 17

Describe the reaction of Na and O2 in air and give the flame colour produced when Na2O is burnt.

Answer 17

Vigorous
Yellow flame

Question 18

Describe the reaction of Mg and O2 in air and give the flame colour produced when MgO is burnt.

Answer 18

Vigorous
Brilliant white flame

Question 19

Describe the reaction of Al and O2 in air and give the flame colour produced when Al2O3 is burnt.

Answer 19

Slow reaction
No flame colour

Question 20

Describe the reaction of Si and O2 in air and give the flame colour produced when SiO2 is burnt.

Answer 20

Slow reaction
No flame colour

Question 21

Describe the reaction of P and O2 in air and give the flame colour produced when P4O10 is burnt.

Answer 21

Spontaneously combusts
Brilliant white flame

Question 22

Describe the reaction of S and O2 in air and give the flame colour produced when SO2 is burnt.

Answer 22

Burns steadily
Blue flame

Question 23

Which period 3 oxide has the highest melting point?

Answer 23

MgO

Question 24

Explain why MgO has a higher melting point than Na2O.

Answer 24

Mg forms 2+ ions. They have a higher charge than Na+ ions, therefore they form stronger ionic bonds that require more energy to be overcome.

Question 24

Explain why Al2O3 has a lower melting point than MgO. Explain how this makes Al2O3 partially covalent.

Answer 24

The difference in electronegativity between Al and O is lower than the difference between Mg and O. This means that O2- ions in Al2O3 can't attract the electrons in the metal-oxygen bond as strongly.

Question 25

Explain why SiO2 has a high melting point.

Answer 25

It is macromolecular, so all bonds are covalent, which are very strong so require lots of energy to be overcome.

Question 26

Explain why P4O10 and SO2 have low melting points.

Answer 26

They have a simple covalent structure so VDW and permanent dipole-dipole forces require little energy to be overcome.

Question 27

What do ionic oxides do in water and what do they form?

Answer 27

They dissolve in water and accept protons to form hydroxide ions.

Question 28

When simple covalent oxides dissolve in water, what do they form? What is formed when they dissociate in solution?

Answer 28

Acidic solutions When they dissociate in solution, a conjugate base is formed.

Question 29

Give an equation for the reaction of P4O10 with water to form an acid. Name the acid formed.

Answer 29

P4O10 + 6H2O -> 4H3PO Phosphoric acid

Question 30

Give an equation for the reaction of SO2 with water to form an acid. Name the acid formed.

Answer 30

SO2 + H2O -> H2SO3 Sulfurous acid

Question 31

Give an equation for the reaction of SO3 with water to form an acid. Name the acid formed.

Answer 31

SO3 + H2O -> H2SO4 Sulfuric acid

Question 32

Give an equation to show the dissociation of H3PO4 in water.

Answer 32

H3PO4 -> 3H+ + PO4 3-

Question 33

Give an equation to show the dissociation of H2SO3 in water.

Answer 33

H2SO3 -> 2H+ + SO3 2-

Question 34

Give an equation to show the dissociation of H2SO4 in water.

Answer 34

H2SO4 -> 2H+ + SO4 2-

Question 35

Why are giant covalent molecules such as SiO2 classed as acids despite being insoluble in water?

Answer 35

They react with bases.

Question 36

Why is Al2O3 insoluble in water?

Answer 36

Partially ionic and partially covalent

Question 37

Give an equation to show the reaction of Na2O with HCl.

Answer 37

Na2O + 2HCl -> 2NaCl + H2O

Question 38

Give an equation to show the reaction of MgO with H2SO4.

Answer 38

MgO + H2SO4 -> MgSO4 + H2O

Question 39

What do Na2O and MgO do to acids?

Answer 39

They neutralise them.

Question 40

Give an equation for SiO2 and 2NaOH.

Answer 40

SiO2 + 2NaOH -> Na2SiO3 + H2O

Question 41

Give an equation for P4O10 and 12NaOH.

Answer 41

P4O10 + 12NaOH -> 4Na3PO4 + 6H2O

Question 42

Give an equation for SO2 and 2NaOH.

Answer 42

SO2 + 2NaOH -> Na2SO3 + H2O

Question 43

Give an equation for SO2 and 2NaOH.

Answer 43

SO2 + 2NaOH -> Na2SO3 + H2O

Question 44

Give an equation for SO3 and 2NaOH.

Answer 44

SO3 + 2NaOH -> Na2SO4

Question 45

What do SiO2, P4O10 and SO2/SO3 do to bases?

Answer 45

Neutralise them

Question 46

What does Al2O3 do to acids and bases?

Answer 46

Neutralises them

Question 47

What is formed when Al2O3 reacts with acids and bases?

Answer 47

Salts

Question 48

Give an equation for the reaction of Al2O3 with 3H2SO4.

Answer 48

Al2O3 + 3H2SO4 -> Al2(SO4)3 + 3H2O

Question 49

Give an equation for the reaction of Al2O3 with 3H2O and 2NaOH.

Answer 49

Al2O3 + 2NaOH + 3H2O -> 2NaAl(OH)4