Chemical Properties Of Period 3

Question 1

Reaction of sodium and magnesium with water

Answer 1

Sodium:
2Na + 2H2O ——> 2NaOH + H2
- vigorous reaction, fizzing, exothermic, PH 13-14
Magnesium:
Mg + 2H2O ——> Mg(OH)2 +H2
- PH 10 (less soluble), slower reaction
Steam:
Mg + H2O ——> MgO + H2
- faster reaction

Question 2

Reaction of sodium and magnesium with oxygen

Answer 2

Sodium:
4Na + O2 ——> 2NaO2
- burns with bright yellow flame, forms white powder

Magnesium:
2Mg + O2 ——> 2MgO
- burns with bright white flame, forms white powder

Question 3

Reaction of aluminium and silicon with oxygen

Answer 3

Aluminium:
4Al + 3O2 ——> 2Al2O3
- burns with white flame

Silicon:
Si + O2 ——> SiO2

Question 4

Reaction of phosphorus and sulfur with oxygen

Answer 4

Phosphorous:
4P + 5O2 ——> P4O10
2 allotropes of phosphorus- white and red
White reacts vigorously, ignites, white solid white smoke.
Red needs to be heated before reacting, white solid white smoke.

Sulfur:
S + O2 ——> SO2 (most common)
2S + 3O2 ——> 2SO3
- burns with blue flame, colourless, eggy smell

Question 5

Melting point of oxides

Answer 5

Na2O- ionic lattice, High m.p
MgO- ionic lattice, high m.p
Al2O3- ionic lattice, high m.p
SiO2- giant Covalent, high m.p
P4O10- simple covalent, high but lower than giant
SO3- covalent, lower (liquid at room temp)
SO2- covalent- lowest (gas at room temp)

Question 6

Reaction of Na2O and MgO with water

Answer 6

Na2O + H2O ——> 2NaOH
- strong base PH 13-14

MgO + H2O ——> Mg(OH)2
- PH 9-10

Question 7

P4O10 reaction with water

Answer 7

P4O10 + 6H2O ——> 4H3PO4
- vigorous reaction, PH 1-2, forms a tetrahedral molecule

Question 8

Reaction of SO3 and SO2 with water

Answer 8

SO3 + H2O ——> H2SO4
- vigorous reaction, PH 0-1, tetrahedral

SO2 + H2O ——> H2SO3
- PH 2-3, trigonal pyramidal