U2 S3- Period 3 Elements

Question 1

sodium reaction with cold water

Answer 1

2Na + 2H2O —> 2NaOH + H2

Question 2

Sodium reaction with cold water observation

Answer 2

1-Vigorously 
2-molten ball on surface
3-effervescence 
4-H2 gas
5-NaOH (strong alkaline solution)

Question 3

Magnesium reaction with cold water

Answer 3

Mg + 2H2O –> MgO + H2

Question 4

Magnesium reaction with cold water observation

Answer 4

1- reacts very slowly

2-Mg(OH)2 (weak alkaline))

Question 5

why is the solution of Mg(OH)2 weakly alkaline

Answer 5

• Mg(OH)2 is not very soluble in water

- so few OH- ions produced

Question 6

Magnesium reacts faster with

Answer 6

1-steam

2-more kinetic energy to form MgO

Question 7

Magnesium reaction with steam

Answer 7

Mg + H2O –> MgO + H2

Question 8

Period 3 reactions with air and rate

Answer 8

2Na + 1/2O2 --> Na2O  VIGOUROUS
Mg + 1/2O2 --> MgO  VIGOROUS
2Al + 1 1/2O2 --> Al2O3 SLOW
Si + O2 --> SiO2 SLOW
P4 + SO2 --> P4O10 SPONTANEOUSLY COMBUSTS
S + O2 --> SO2  BURNS STEADILY

Question 9

Na and O2 colour flame

Answer 9

2Na + 1/2O2 –> Na2O YELLOW + WHITE PTT

Question 10

Mg and O2 colour flame

Answer 10

Mg + 1/2O2 –> MgO BRILLIANT WHITE + WHITE PTT

Question 11

Al and O2 colour flame

Answer 11

2Al + 1 1/2O2 –> Al2O3 N/A + WHITE PTT

Question 12

Si and O2 colour flame

Answer 12

Si + O2 –> SiO2 N/A + WHITE PTT

Question 13

P and o2 colour flame

Answer 13

P4 + SO2 –> P4O10 BRILLIANT WHITE + WHITE PTT

Question 14

s and O2 colour flame

Answer 14

S + O2 –> SO2 BLUE + COLOURLESS GAS (SO2)

Question 15

Catalyst with SO2 + 1/2O2 –> SO3

Answer 15

-vanadium (V2O5)

Question 16

amphoteric

Answer 16

has properties of acid and base

Question 17

Melting points of Na2O, MgO, Al2O3

Answer 17

1- Giant ionic lattices

2-strong forces of electrostatic attraction between positive ions and e-

Question 18

Why is the melting point of MgO higher than Na2O

Answer 18

1- Mg2+ attract O2- more strong electrostatic attraction
than the 2 na+ attracted to O2-
2-more energy required to break ionic bonds

Question 19

why is Al2O3 melting point lower than expected

Answer 19

1- Al3+ ions distort the oxygen’s electron cloud making it partially ionic and partially covalent

Question 20

SiO2 melting point

Answer 20

1-Macromolecular/Giant covalent
2-Strong covalent bonds
3-lots of E required to break
4-High MP

Question 21

melting points of P4O10 and SO3

Answer 21

1-simple molecular/compounds
2-molecules attracted by weak IMF VDWS and induced dipole-dipole
3-Low MP

Question 22

Reactions of Na2O and MgO with water

Answer 22

Na2O + H2O –> 2NaOH

MgO + H2O –> Mg(OH)2

Question 23

why is NaOH strongly alkaline and Mg(OH)2 weakly alkaline

Answer 23

NaOH= more soluble in water Na+ and OH- easier to dissociate into almost completely
Mg(OH)= less soluble in water Mg2+ and OH- harder to dissociate into  slightly

Question 24

SiO2 reactions with water

Answer 24

1-SiO2 macromolecular / giant covalent

2-insoluble in water

Question 25

Al2O3 reactions with water

Answer 25

1-partially ionic and partially covalent due to Al3+ ions distorting the electron charge cloud
2-insoluble in water

Question 26

P4O10, SO3, SO2 reactions with water

Answer 26

P4O10 + 6H2O –> 4H3PO4
SO2 + H2O –> H2SO3
SO3 + H2O –>H2SO4

Question 27

dissociation of H3PO4, H2SO3, H2SO4

Answer 27

H3PO4 –> 3H+ + PO43-
H2SO3 –> 2H+ + SO32-
H2SO4 –> 2H+ + SO42-

Question 28

Neutralisation reaction

Answer 28

ACID + BASE –> SALT + WATER

Question 29

Na2O and MgO reactions with acid and bases

Answer 29

-Na2O + MgO are basic so neutralise acids

Question 30

Al2O3 reactions with acid and bases

Answer 30

amphoteric neutralises both acids or bases

Question 31

P4H10, SO3, SO2 with acids and bases

Answer 31

acidic so neutralise bases