Period 3 elements and oxides

Question 1

Why is sodium more reactive than magnesium?

Answer 1

Sodium is more reactive than magnesium because it takes less energy to lose one electron than it does to lose 2.

Question 2

How does sodium react with water:

Answer 2

• Sodium reacts VIGOROUSLY with cold water, forming a molten ball on the surface, fizzing and Hydrogen gas.
• This reaction PRODUCES SODIUM HYDROXIDE
• so solution is strongly alkaline. (pH 12-14)

Question 3

How does magnesium react with water:

Answer 3

Magnesium reacts VERY SLOWLY with cold water
- forms a WEAK ALKALINE solution (pH9-10)

• thin coating of magnesium hydroxide forms on the metal
• solution is WEAKLY ALKALINE because magnesium hydroxide is NOT VERY SOLUBLE in water

Question 4

Sodium reacting with water equation:

Answer 4

2Na + 2H2O -> 2NaOH + H2

s) (l) (aq) (g

Question 5

Magnesium reacting with water:

Answer 5

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

s) (l) (aq) (g

Question 6

Magnesium reacting with STEAM equation:

Answer 6

Mg+ H2O -> MgO + H2

s) (g) (s) (g

Question 7

What catalyst is used to help form sulfur trioxide

Answer 7

Vanadium catalyst

Question 8

1) sodium with oxygen: sodium oxide

Answer 8

2Na + 1/2 o2 -> Na2O

where reactant metal and final product is in (s) solid state

Question 9

2) Aluminium with oxygen: Aluminium oxide

Answer 9

2Al + 3/2 o2 -> Al2O3

Aluminium oxide is the only equation
where there is 3/2 oxygen

Question 10

3) Phosphorus (p4) with oxygen; Phosphorus (V) oxide

Answer 10

P4 + 5O2 -> P4o10

Phosphorus (V) oxide is the only equation with 5o2

Question 11

4) Magnesium with oxygen: magnesium oxide

Answer 11

Mg + 1/2 O2 -> MgO

Question 12

5) Silicon and oxygen: Silicon oxide

Answer 12

Si + O2 -> Sio2

Question 13

6) Sulfur and oxygen: Sulfur dioxide

Answer 13

S + O2 -> SO2

Question 14

Which metals react slow with AIR?

Answer 14

Silicon and aluminium

• whereas phosphorus SPONATANEOUSLY COMBUSTS.
• Sulfur BURNS READILY
• Sodium and magnesium- VIGOUROUS

Question 15

who has a higher melting point sodium oxide OR magnesium oxide?

Answer 15

Magnesium oxide as Mg forms 2+ ions which require more energy to over come as bonds are stringer than the 1+ Na ions in sodium oxide.

both are known as “giant ionic lattices”

Question 16

Why does Al2O3 have a lower melting point than expected?

Answer 16

not big enough difference in electronegativity between Al and O, as compared to Mg and O.

• which means oxygen ions in Al2o3 don’t attract the electrons in the Al-O bond, which makes aluminium oxide PARTIALLY COVALENT

Question 17

Why does SiO2 have a higher melting point than expected?

Answer 17

Its macromolecular, requires a lot of energy to overcome many strong covalent bonds between atoms.

• hence high MP

Question 18

Why does Phosphorus (V) oxide and sulfur dioxide have a low MP?

Answer 18

This is because both are simple molecular structures
- with weak intermolecular forces of attraction between molecules.

• which require little energy to overcome

Question 19

Which type of oxide is Acidic

Answer 19

COVALENT OXIDES

Question 20

Which type of oxide is Alkaline

Answer 20

IONIC OXIDES

Question 21

Covalent oxides dissociating in water

1) Phosphorus (V) acid:

Answer 21

Firstly, the metal oxide in water.

P4o10 + 6H2O -> 4H3PO4
(s) (l) (aq)

H3PO4 -> 3H+ + PO4 (3-)
(aq) (aq) (aq)

Question 22

Covalent oxides dissociating in water

2) Sulfurous acid/ sulfuric (IV) acid:

Answer 22

SO2 + H2O -> H2SO3
(g) (l) (aq)

H2SO3 -> 2H+ + SO3 (2-)

• all aqueous state symbols

Question 23

Covalent oxides dissociating in water ( sulfur trioxide)

3) Sulfuric (VI) acid:

Answer 23

SO3 + H2O -> H2SO4
(l) (l) (aq)

h2So4 -> 2H+ + SO4 (2-)

Question 24

Is silicon dioxide classified as an acid tho?

Answer 24

Well, its giant covalent structure means that it is insoluble in water.

• HOWEVER, it will react with bases to form salts, so its classified as an acid.

Question 25

What is classified as amphoteric and why?

Answer 25

Aluminium oxide is amphoteric, as it can act as either and acid or a base. This is because it is partly ionic and partly covalent.

Question 26

Neutralisation reaction:

Answer 26

Acid+ Base -> Salt + water

Question 27

Neutralisation reactions : (2) | For basic oxides

Answer 27

Basic oxides neutralise acids: 1) Na2O + 2HCl -> 2NaCl + H2O (s) (aq) (aq) (l) 2) MgO + H2SO4 -> MgSO4 + H2O (s) (aq) (aq) (l)

Question 28

Neutralisation reactions: (4) | For Acidic oxides

Answer 28

- acidic oxides neutralise bases - for the first 2 equations (s),(aq),(aq),(l) - for the last 2, (g),(aq),(aq),(l) 1) SiO2 +2NaOH -> Na2SiO3 + H2O 2) P4O10 + 12 NaOH -> 4Na3PO4 + 6H2O 3) SO2 +NaOH -> Na2SO3 + H2O 4) SO3 + 2NaOH -> Na2SO4 + H2O

Question 29

``` Neutralisation reactions (2) For Amphoteric oxides: ```

Answer 29

Amphoteric oxides neutralise both acids and bases 1) Al2O3 + 3H2SO4 -> Al2(SO4)3 + 3H2O (s) (aq) (aq) (l) 2) Al2O3 + 2NaOH + 3H2O-> 2NaAl(OH) (s) (aq) (l) (aq)