period 3

Question 1

Give an equation, including state symbols, for the reaction of sodium with water

Answer 1

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

Question 2

Give an equation for the reaction of phosphorus(V) oxide with water.
Suggest a pH for the solution formed

Answer 2

P4O10 + 6 H2O → 4 H3PO4

Allow ‒1 to + 1

Question 3

equation + visible change when Na reacts with O2

Answer 3

2Na(s) + ½O2(g) à Na2O(s)
burns brightly w yellow flame forms a white solid

Question 4

equation + visible change when Mg reacts with O2

Answer 4

2Mg(s) + O2(g) à 2MgO(s
This burns brightly in oxygen gas with a brilliant white flame to form a white solid:

Question 5

equation + visible change when Al reacts with O2

Answer 5

4Al(s) + 3O2(g) -> 2Al2O3
bright white flame to produce Aluminium oxide

Question 6

equation + visible change when Si reacts with O2

Answer 6

S(s) + O2(g) -> SO2(s
orange flame

Question 7

What is the trend in bonding across period 3?

Answer 7

Across P3 the bonding changes from being Ionic on the left to covalent on the right

Question 8

Why does MgO have the highest melting point of all the P3 oxides?

Answer 8

• MgO has ionic bonds.
• There are strong electrostatic forces of attraction between oppositely charged ions.
• These require a lot of energy to overcome.

Question 9

Why does Al2O3 have more covalent character then MgO?

Answer 9

• The Al3+ ion is smaller than the Mg2+ ion.
• This means the Al3+ ion is more polarising than the Mg2+ ion.
• This distorts the electron cloud around the O2- ion more so that there is more electron density shared between the two ions.

Question 10

Explain why sodium oxide forms an alkaline solution when it reacts with water

Answer 10

Sodium oxide contains O2– ions

These O2– ions react with water forming OH– ions

OR O2– + H2O 2OH

Question 11

Name two insoluble oxides

Answer 11

aluminium oxide
silicon dioxide

Question 12

define amphoteric

Answer 12

can act as acid or base

Question 13

equation + visible change when P reacts with O2

Answer 13

P4(s) + 5O2(g) -> P4O10
White P(v)