Period 3

Question 1

How does Na react with water?

Answer 1

Sodium reacts vigorously with water to form NaOH and H2. There is fizzing.

Question 2

How does Mg react with water in a liquid state?

Answer 2

Magnesium reacts slowly with cold water forming a weak solution of Mg(OH)2. The alkaline solution is weak as Mg(OH)2 is sparingly soluble.

Question 3

How does Mg react with steam?

Answer 3

Reacts very fast to form MgO and H2.

Question 4

How does phosphorus react with oxygen?

Answer 4

Forms phosphorus (V) oxide. P4(s) + 5O2(g) –> P4O10(s).

Question 5

How does sulfur react with oxygen?

Answer 5

Sulfur forms SO2 (oxidation number +4) but at higher temperatures and the catalyst V2O5, SO3 can be made (oxidation state +6).

Question 6

Which elements react quickly with air?

Answer 6

Na, Mg, Al (if powdered), P4 spontaneously combusts.

Question 7

Why does Al2O3 have a slightly lower melting point than MgO?

Answer 7

Al3+ ions distort the electron cloud of oxygen. This means there is some covalent character as well as expected ionic interactions. This means less energy is required to break the bonds.

Question 8

What type of structure does P4O10 have?

Answer 8

A simple covalent structure.

Question 9

What pHs do the ionic oxides form when reacted with water?

Answer 9

Sodium oxide forms a pH of 12-14. Magnesium oxide forms a pH of 9-10.

Question 10

What pHs do the simple covalent oxides form when reacted with water?

Answer 10

Phosphorus oxide forms phosphoric (V) acid. Sulphur dioxide forms sulphurous acid. Sulphur trioxide forms sulphuric acid.

Question 11

Show the reaction between P4O10 and H20:

Answer 11

P4O10 + H20 –> 4H3PO4

H3PO4 –> 3H+ + PO4 3-

Question 12

How do silicon and aluminum oxide react with water?

Answer 12

Silicon dioxide has a giant covalent structure so is insoluble in water (still an acid as reacts with a base to form salt). Aluminum oxide is amphoteric so it acts as a base and an acid to form salts however it is also insoluble in water (covalent and ionic character).

Question 13

What is the standard equation for acid-base reaction?

Answer 13

acid + base –> salt + water

Question 14

How does silicon dioxide react with sodium hydroxide?

Answer 14

SiO2 + 2NaOH –> Na2SiO4 + H20

Question 15

How does aluminum oxide react with NaOH and H2SO4?

Answer 15

Al2O3 + 2NaOH + 3H20 –> 2NaAl(OH)4 (sodium aluminate)

3H2SO4 + Al2O3 –> Al2(SO4)3 + 3H2O