22 Periodicity

Question 1

Magnesium and cold water

Answer 1

Mg(s) + 2H2O (l) ➡️ Mg(OH)2 (aq) + H2
Reaction slow at room temp

Mg(s) + H2O ➡️ MgO (s) + H2

Both redox reactions

Question 2

Sodium and cold water

Answer 2

2Na(s) + 2H2O(l). ➡️ 2NaOH (aq) + H2 (g)

Vigorous
Sodium floats on the surface and fizzes rapidly

Question 3

sodium
magnesium
aluminum

Answer 3

metallic
shiny (when freshly exposed to air)
conduct electricity
react with dilute acids to give hydrogen and salts

Question 4

silicon

Answer 4

semi-metal (metalloid)
conduct electricity to some extent
semiconductor

Question 5

Phosphorus
sulfur
chlorine

Answer 5

non-metals
do not conduct electricity
low melting and boiling points

Question 6

argon

Answer 6

chemically unreactive

exists as separate atoms

Question 7

sodium and oxygen

Answer 7

burns brightly in air
with a yellow flame (because of sodium peroxide Na2O2)
2Na (s) + 1/2 O2 (g) ➡️ Na2O (s)

Question 8

period 3 and oxygen

Answer 8

relativity reactive

reactions are exothermic

Question 9

magnesium and oxygen

Answer 9

strip of magnesium ribbon burns in air with a bright white flame
white power produced is magnesium oxide

2Mg (s) + O2(g) ➡️ 2MgO

Question 10

aluminium and oxygen

Answer 10

burns brightly

4Al (s) + 3O2(g) ➡️ 2Al2O3

Question 11

aluminium

Answer 11

reactive metal but it is always coated with a strongly bonded structure layer of oxide, this protects it from further reaction
so it appears as an unreceptive metal

Question 12

silicon and oxygen

Answer 12

Si (s) + O2 (g) ➡️ SiO2 (s)

Question 13

red phosphorus and oxygen

Answer 13

has to be heated before it will react with oxygen

4P(s) + 5O2(g) ➡️ P4O10(s)

Question 14

white phosphorus and oxygen

Answer 14

spontaneously ignites in air

4P(s) + 5O2(g) ➡️ P4O10(s)

limited supply of oxygen
4P(s) + 5O2(g) ➡️ P2O3(s)

Question 15

sulfur and oxygen

Answer 15

when sulfur powder is heated and lowered into a gas jar of oxygen, it burns with a blue flame to form the colourless gas sulfur dioxide

S(s) + O2(g) ➡️ SO2(g)

Question 16

sodium oxide
magnesium oxide
aluminum oxide

Answer 16

giant ionic lattices

high melting points

Question 17

Aluminum oxide

Answer 17

ionic but has some covalent character

small ion with a large positive charge

Question 18

silicon oxide

Answer 18

ginat covalent (macromolecular) structure
high melting point because many strong covalent bonds must be broken to melt it

Question 19

phosphorus and sulfur oxide

Answer 19

covalently bonded molecules
intermolecule forces are weak van Der Waals and dipole-dipole forces
relatively low melting points

Question 20

structure of sodium oxide

Answer 20

giant ionic

Question 21

structure of magnesium oxide

Answer 21

giant ionic

Question 22

structure of aluminium oxide

Answer 22

giant ionic

Question 23

structure of silicon oxide

Answer 23

giant covalent ( macromolecular)

Question 24

structure of phosphorus oxide

Answer 24

molecular

Question 25

structure of sulfur oxide

Answer 25

molecular

Question 26

sodium oxide (basic)

Answer 26

Na2O (s) + H2O (l) ➡️ 2Na+(aq) + 2OH-

pH = 14

Question 27

Magnesium oxide (basic)

Answer 27

magnesium hydroxide is sparing soluble
MgO(s) + H20(l) ➡️ Mg(OH)2(s)

Mg(OH)2(s) Mg2+ (aq) + 2OH- (aq)
pH = 9

Question 28

insoluble oxides

Answer 28

aluminium oxide and silicon dioxide are both insoluble in water

(silicon dioxide are sand)

Question 29

phosphorus pentoxide and water (acidic )

Answer 29

phosphorus pentoxide reacts quite violently with water to produce an acid solution of phosphoric acid

P4O10(s) + 6H2O(l) ➡️ 4H3PO4(aq)

H3PO4(aq) H+(aq) + H2PO4-(aq)
pH = 1-2

Question 30

sulfur dioxide and water (acidic)

Answer 30

sulfur dioxide is fairly soluble in water and reacts to give an acidic solution of sulphuric acid.

SO2(g) + H20(l) ➡️ H2SO3

H2SO3 H+ (aq) + HSO3-(aq)
pH = 2-3

Question 31

sulfur trioxide and water (acidic)

Answer 31

sulfur triode reacts violently with water to produce sulphuric acid

SO3(g) + H2O(l) ➡️ H2SO4(aq) ➡️ H+(aq) + HSO4-(aq)
pH = 0-1

Question 32

sodium and magnesium oxide and acids

Answer 32

react with an acids to give a salt and water only

Na2O(s) + H2SO4(aq) ➡️ Na2SO4(aq) + H2O(l)
MgO(s) + 2HCl (aq) ➡️ MgCl2(aq) +H2O

Question 33

Aluminium oxide and acid

Answer 33

Al2O3(s) + 6HCl(aq) ➡️ 2AlCl3(aq) + 3H2O(l)

Question 34

Aluminium oxide and alkali

Answer 34

Al2O3(s) + 2NaOH(aq) +3H2O ➡️ 2NaAl(OH)4(aq)

NaOH hot and concentrated

Question 35

silicon dioxide and base

Answer 35

reacts a weak acid with a strong base

SiO2(s) + 2NaOH(aq) ➡️ Na2SiO3(aq) + H2O(l)

Question 36

iron production

Answer 36

iron is produced in blast furnaces
calcium oxide reacts with the impurity silicon dioxide to produce a liquid slag.
SiO2(s) + CaO(l) ➡️ CaSiO3(l)

Question 37

phosphorous pentoxide

Answer 37

reaction of phosphorus pentoxide with an alkali to make phosphorus acid

H3PO4(aq) + NaOH(aq) ➡️ NaH2PO4(aq) + H2O(l)
NaH2PO4(aq) + NaOH(aq) ➡️ Na2HPO4(aq) + H2O(l)
NaHPO4(aq) + NaOH(aq) ➡️ Na3PO4(aq) + H2O(l)

3NaOH(aq) + H3PO4(aq) ➡️ Na3PO4(aq) + 3H2O(l)

Question 38

sulfur dioxyde and alkali

Answer 38

SO2(aq) + NaOH(aq) ➡️ NaHSO3(aq)

NaHSO3(aq) + NaOH(aq) ➡️ Na2SO3(aq) + H2O(l)

Question 39

calcium sulfite

Answer 39

sulfur dioxide react with base calcium oxide to form calcium sulfite. this is the first step of one of the methods of removing sulfur dioxide from flue gases in power stations
CaO(s) + SO2(g) ➡️ CaSO3(s)

calcium sulfite is further converted to calcium sulphate and sold as gypsum for plastering