Chapter 22- Periodicity

Question 1

What is the reaction between sodium and water and what are the observations?

Answer 1

2Na (s) + 2H2O (l) —> 2NaOH (aq) + H2 (g)
Vigorous, sodium fizzes on surface

Question 2

What is the reaction between magnesium and water at room temp?

Answer 2

Mg (s) + 2H2O (l) —> Mg(OH)2 (aq) + H2 (g)
Very slow at RT, few H2 bubbles after days

Question 3

What is the reaction between magnesium and steam?

Answer 3

Mg (s) + H2O (g) —> MgO (s) + H2 (g)
Violent, burns with bright white flame

Question 4

How do the reactions between sodium and water and magnesium and water compare?

Answer 4

Both react ionically to form positive ions however Na is more reactive as it loses one electron to form 1+ ions while Mg loses two electrons to form 2+ ions which requires more energy

Question 5

How do period 3 elements react with oxygen?

Answer 5

React to form oxides with the period 3 element in their highest oxidation state, often their group number

Question 6

What is the reaction between sodium and oxygen and what are some observations?

Answer 6

2Na (s) + 0.5 O2 (g) –> Na2O (s)
Yellow flame

Question 7

What is the reaction between magnesium and oxygen and what are some observations?

Answer 7

2Mg (s) + O2 (g) –> 2MgO (s)
Bright white flame

Question 8

What is the reaction between aluminium and oxygen?

Answer 8

4Al (s) + 3O2 (g) –> 2Al2O3 (s)

Question 9

What is the reaction between silicon and oxygen?

Answer 9

Si (s) + O2 (g) –> SiO2 (s)

Question 10

What is the reaction between phosphorus and oxygen and what are some observations?

Answer 10

4P (s) + 5O2 (g) –> P4O10 (s)
White phosphorus spontaneously ignites and white smoke is given off

Question 11

What is the common reaction between sulfur and oxygen and what are some observations?

Answer 11

S (s) + O2 (g) –> SO2 (g)
Blue flame

Question 12

What is the other reaction between sulfur and oxygen and what are the conditions?

Answer 12

2S (s) + 3O2 (g) –> 2SO3 (g)
Requires high temperature and a catalyst

Question 13

What is the structure and bonding of sodium and magnesium oxides?

Answer 13

Giant ionic lattices
Ionic as a metal and non-metal are bonded and there is a large difference in electronegativities

Question 14

What is the structure and bonding of aluminium oxide?

Answer 14

Ionic with covalent character as a metal and non-metal are bonded however aluminium forms a small ion with high charge (3+) so it is close to the oxide ion and distorts its electron cloud

Question 15

What is the structure and bonding of silicon oxide?

Answer 15

Giant covalent (macromolecular) structure
Many bonds throughout so high melting point

Question 16

What is the structure and bonding of phosphorus and sulfur oxides?

Answer 16

Simple covalent structures
Covalent bonds in molecules and weak VdWs and dipole-dipole attractions between the molecules so a lower melting point, hence sulfur oxides being gaseous at RT

Question 17

What is the general trend in melting points of oxides across period 3 and why is this?

Answer 17

Peaks at MgO then decreases, MgO and Al2O3 are highest due to metal ions with greater charges

Question 18

What is an alkaline solution?

Answer 18

A solution with a pH of 8-14.

Question 19

How are alkaline solutions formed from period 3 oxides?

Answer 19

Formed when basic ionic oxides, Na2O or MgO, dissolve in water
The oxide ions accept protons from the water to form OH- ions.

Question 20

Which are the basic period 3 oxides?

Answer 20

Sodium oxide and magnesium oxide

Question 21

Which period 3 oxides are insoluble?

Answer 21

Aluminium oxide and silicon dioxide

Question 22

What is an acidic solution?

Answer 22

Solutions with a pH of 0-6

Question 23

How are acidic solutions formed from period 3 oxides?

Answer 23

Simple covalent oxides of phosphorus and sulfur react with water and the product dissociates when aqueous, releasing H+ ions

Question 24

What are the acidic oxides?

Answer 24

Phosphorous oxide and sulfur oxides

Question 25

What is the reaction between sodium oxide/ magnesium oxide and water and what are the pHs?

Answer 25

Na2O + H2O –> 2NaOH, pH 14
MgO + H2O –> Mg(OH)2, pH 9

Question 26

What is the reaction between phosphorous oxide and water and what is the resulting pH?

Answer 26

P4O10 (s) + 6H2O (l) –> 4H3PO4 (aq)
When in solution, forms an acid with pH 1-2

Question 27

What is the reaction between sulfur dioxide and water and what is the resulting pH?

Answer 27

SO2 (g) + H2O (l) –> H2SO3 (aq)
When in solution, forms an acid with pH 2-3

Question 28

What is the reaction between sulfur trioxide and water and what is the resulting pH?

Answer 28

SO3 (g) + H2O (l) –> H2SO4 (aq)
When in solution, forms an acid with pH 0-1

Question 29

What is dissocation?

Answer 29

Splitting into ions, ie to produce an acid as a H+ ion and conjugate anion is produced

Question 30

How do basic, ionic oxides react with acids?

Answer 30

Produce a salt and water in a neutralisation reaction

Question 31

What is a property of aluminium oxide and why does it have this property?

Answer 31

It is amphoteric meaning it can act as both an acid and an alkali due to it having ionic bonds with covalent character.

Question 32

How does aluminium oxide react with acids and alkalis?

Answer 32

Reacts to product a salt and water in neutralisation reactions with both

Question 33

How do the covalent oxides react with bases?

Answer 33

Produce a salt and water in neutralisation reactions