4I- Period 3 And Oxides

Question 1

Reaction of Na with water

Answer 1

Vigorous, Na floats on surface, fizzes rapidly, NaOH solution is produced

2Na + 2H2O —> 2NaOH + H2

Question 2

Reaction of Mg with water

Answer 2

Room temp
Few H2 bubbles produced, pH 10 solution produced
Mg + 2H2O (l) —> Mg(OH)2(aq) + H2

Heated
Bright white light, effervescence
Mg + H2O(g) —> MgO —> H2

Question 3

Reaction of Na with oxygen

Answer 3

Burns in a yellow flame, produces white Na2O

2Na + 0.5O2 —> Na2O

Question 4

Reaction of Mg with oxygen

Answer 4

Bright white flame, white smoke, white MgO powder

2Mg + O2 —> 2MgO

Question 5

Reaction of Al with oxygen

Answer 5

White flame, white smoke, white powder produced

4Al + 3O2 —> 2Al2O3

Question 6

Reaction of Si with oxygen

Answer 6

White flame, white smoke, white solid

Si + O2 —> SiO2

Question 7

Reaction of P with oxygen

Answer 7

Burn with a white flame, white smoke

4P + 5O2 —> P4O10

Question 8

Reaction of S with oxygen

Answer 8

Blue flame, forms colourless SO2

S + O2 —> SO2

Question 9

Trends in the reaction of period 3 elements with oxygen

Answer 9

Metal oxides (Na2O, MgO, Al2O3)
Ionic, high MPs, giant ionic lattice strong electrostatic forces of attraction between oppositely charged ions, Al2O3 has lower electronegativity difference so slightly covalent

Simple molecular oxides (P4O10, SO2)
Weak intermolecular forces between molecules, low MPs,

Giant covalent oxides (SiO2)
Many strong covalent bonds between atoms, very high MPs

Question 10

Reaction of Na2O and MgO (ionic) with oxygen

Answer 10

Na2O + H2O —> 2Na+(aq) + 2OH-(aq)
Vigorous exothermic reaction
pH 13

MgO + H2O —> Mg(OH)2
pH 9
Sparingly soluble so lower pH

Question 11

Reactions of Al2O3 and SiO2 with water

Answer 11

Don’t dissolve in water, high strength ionic lattice Al2O3 and giant covalent structure SiO2, pH 7

Question 12

Reactions of P4O10 SO2 and SO3 with water

Answer 12

P4O10 + 6H2O —> 4H3PO4
pH 0, vigorous exothermic reaction

SO2 + H2O —> H2SO3
pH 3, weak acid

SO3 + H2O —> H2SO4
pH 0

Question 13

Trend across the period for oxides reacting with water

Answer 13

LHS (metal oxides) form alkali solutions
Al2O3 and SiO2 form neutral solutions
RHS (non metal oxides) form acidic solutions

Question 14

Equations to show the formation of acids and ions formed for P4O10 SO2 and SO3 reaction with water

Answer 14

P4O10 + 6H2O —> 4H3PO4
H3PO4 (aq) <—> H+(aq) + H2PO4-(aq)

SO2 + H2O —> H2SO3
H2SO3(aq) <—> H+(aq) + HSO3-(aq)

SO3 + H2O —> H2SO4
H2SO4 —> H+(aq) + HSO4-(aq)