Period 3

Question 1

Na reaction with water

Answer 1

2Na + 2H2O = 2NaOH + H2
Alkaline solution as strong base fully dissociates
Reacts with cold water vigorously and fizzes gas of H2

Question 2

Mg reaction with water (2)

Answer 2

Mg + 2H2O (l) = mg(OH)2 + H2
Reacts slowly as sparingly soluble in water
Mg + H2O(g) = MgO + H2
Forms white solid and bright light

Question 3

Na with O2

Answer 3

Na + 1/2 O2 = NaO
Very fast
Orange flame and white ppt

Question 4

Mg and O2

Answer 4

Mg + 1/2 O2 = MgO
Very fast
White flames and white ppt

Question 5

Al with O2

Answer 5

2Al + 3/2 O2 = Al2O3
Slow but when powdered is fast
Sprinkle powder then you get bright light sparks

Question 6

Si with O2

Answer 6

Si + O2 = SiO2
Slow
Orange flame
White solid

Question 7

P4 and O2

Answer 7

P4 +5O2 = P4O10
Spontaneously combusts
White flames and white fumes

Question 8

S + O2

Answer 8

S + O2 = SO2
High temperature and catalyst SO3 can be made
Steadily burns
Pale blue flames and colourless gas

Question 9

Al2O3 as amphoteric

Answer 9

Base = 2NaOH + Al2O3 + H2O = 2NaAl(OH)4
Acid = 3H2SO4 + Al2O3 = Al2(SO4)3 + 3 H2O

Question 10

Why does Al2O3 have a lower melting point than MgO

Answer 10

Al 3+ is smaller than Mg2+
More polarising than mg 2+
Distorts electron cloud around O2
More electron density shared between 2 ions

Question 11

Bonding in NaO

Answer 11

Ionic

Question 12

Bonding in MgO

Answer 12

Ionic

Question 13

Bonding in Al2O3

Answer 13

Ionic

Question 14

Binding in SiO2

Answer 14

Covelant. Macromolecular

Question 15

Bonding in SO2

Answer 15

Covelant simple molecular

Question 16

Bonding in P4O10

Answer 16

Covelant simple molecular

Question 17

Acid base reaction

Answer 17

Forms salt and water
SO3 = H2SO4
SO2 = H2SO3
P4O10 = H3PO4

Question 18

Test tube reaction for NaO and P4O10

Answer 18

React both with water
Measure PH
NaO should form a strong base

Question 19

Describe method to determine melting point

Answer 19

Heat sample slowly in crucible
Until impurities are seen