period 3 oxides melting points + dissolving

Question 1

why is sodium oxides melting point high ?

Answer 1

• because it is ionic
• therefore contains ionic bonds which are strong electrostatic forces of attraction between oppositely charged ions
• so requires a great deal of energy to break those electrostatic forces of attraction

Question 2

why is magnesium oxides melting point higher than sodium oxides ?

Answer 2

• due to the magnesium ion having a higher relative charge due to being a 2+ ion where as Na is only a 1+ ion
• sodium is more polarising and so it attracts the oxide ion more towards itself
• so requires more energy to overcome the strong electrostatic forces of attraction

Question 3

what kind of properties does the aluminium oxide have ?

Answer 3

• it has some covalent properties

Question 4

why does aluminium oxide show some covalent properties ?

Answer 4

• because there is a small difference in electronegativity betweeen the aluminium ion and oxide ion
• aluminium also has a larger nuclear charge so it is more polarising
• able to attract oxygens electron cloud more readily

Question 5

what kind of structure is silicon oxide ?

Answer 5

• giant covalent

Question 6

what is the relative melting point of silicon oxide ?

Answer 6

• high mpt
• because it is macromolecular
• so has lots of covalent bonds which collectively provide strength
• so require a great deal of energy to overcome

Question 7

what kind of structure does phosphorus oxide , sulfur dioxide and sulfur trioxide have ?

Answer 7

• simple molecular

Question 8

why does phosphorus have a higher mpt than sulfur ?

Answer 8

• because sulfur is a bigger molecule
• it has more van der waals forces
• which collectively provide strength
• as the more van der waals forces the greater the energy required to overcome the v.d.w forces

Question 9

when metallic oxides dissolve in solution s, what do they form ?

Answer 9

• alkalis

Question 10

when non-metallic oxides dissolve, what do they form ?

Answer 10

• acids

Question 11

what is the approximate ph of Na2O ?

Answer 11

13

Question 12

what is the approximate ph of MgO ?

Answer 12

9

Question 13

what is the approximate ph of Al2O3 ?

Answer 13

7
- it is insoluble so won’t affect ph

Question 14

what is the approximate ph of SiO2 ?

Answer 14

7
- it is insoluble so will not affect the pH

Question 15

what is the approximate ph of P4O10 ?

Answer 15

0

Question 16

what is the approximate ph of SO2 ?

Answer 16

3

Question 17

what is the approximate ph of SO3 ?

Answer 17

0