Period 3 Oxides

Question 1

Periodicity (define)

Answer 1

The regular repeating pattern of physical or chemical properties going across periods

Question 2

What’s the trend in atomic radius across period 3?

Answer 2

Atomic radii decrease across a period, because the increased number of protons create more positive charge attraction for electrons which are in the same shell with similar shielding.

Question 3

What’s the trend in first ionisation energy across a period?

Answer 3

There is a general trend across to increase. This is due to increasing number of protons as the electrons are being added to the same shell.

Question 4

What are the two elements that deviate from the first ionisation energy trend?

Answer 4

Al and S

Question 5

Explain why Al deviates from the first ionisation energy trend

Answer 5

Al has the first electron in the 3p Subshell which is higher in energy and further away in space, so easier to remove

Question 6

Explain why S deviates from the first ionisation energy trend

Answer 6

S has the first example of spin pair repulsion in 3p so is easier to remove.

Question 7

State and explain the trend in melting point of period 3 elements for the metals

Answer 7

For Na, Mg, Al-Metallic bonding : strong bonding-gets stronger the more electrons there are in the outer shell that are released to the sea of electrons. A smaller sized ion with a greater positive charge also makes the bonding stronger. Higher energy is needed to break bonds.

Question 8

State and explain the trend in melting point of period 3 elements (including graph) for the non-metals

Answer 8

Si is Macromolecular: many strong covalent bonds between atoms, high energy needed to break covalent bonds-very high mp+bp
Cl2 (g), S8 (s), P4 (S)-simple molecular: weak van der waals between molecules, so little energy is needed to break them low mp + bp
S8 has a higher mp than P4 because it has more electrons (S8=128)(P4=60) so has stronger van der waal’s forces between molecules. Ar is monoatomic has weak van der waal’s forces between atoms

Question 9

What’s the graph to show the trend in melting point of period 3?

Answer 9

Question 10

First ionisation energy definition

Answer 10

The enthalpy change when 1 mole of gaseous atoms have 1 mole of electrons removed from them

Question 11

Generic equation for first ionisation

Answer 11

X(g) –> X+(g) + e-

Question 12

Give the equations for the reaction of Na with water

Answer 12

Na (s) + 2 H2O (l) –> 2 NaOH (aq) + H2(g)

Question 13

Give the equation for the reaction of Mg with steam

Answer 13

Mg (s) + H2O (g) –> MgO (s) + H2(g)

Question 14

Colour of flame and product of combustion of Na and equation

Answer 14

Yellow flame with a white solid
4 Na (s) + O2(g) –> 2 Na2O (s)

Question 15

Colour of flame and product of combustion of Mg and equation

Answer 15

White flame, White solid.
2Mg (s) + O2(g)–> 2MgO (s

Question 16

Colour of flame and product of combustion of Al and equation

Answer 16

White flame, White Solid,
4Al + 3O2(g) –> 2Al2O3(s)

Question 17

Colour of flame and product and equation for the reaction between oxygen and Si

Answer 17

White flame, White solid
Si + O2(g) –> SiO2(s)

Question 18

Colour of flame and product and equation for the reaction between oxygen and P

Answer 18

White flame, White solid
4P + 5O2(g) –> P4O10(s)

Question 19

Colour of flame and product and equation for the reaction between oxygen and S

Answer 19

Blue flame, forms a choking gas
S+ O2(g) –> SO2(g)
S+ 3/2 O2(g) –> SO3(g)

Question 20

Trend in Melting point of ionic period 3 oxides (metal oxides)

Answer 20

The metal oxides (Na2O, MgO, Al2O3) are ionic. They have high melting points. They have Ionic giant lattice structures: strong forces of attraction between ions so higher mp. The increased charge on the cation makes the ionic forces stronger (bigger lattice enthalpies of dissociation) going from Na to Al so leading to increasing melting points.

Question 21

Trend in period 3 Melting points - SiO2

Answer 21

SiO2is Macromolecular: It has many very strong covalent bonds between atoms. High energy needed to break the many strong covalent bonds-very high mp +bp

Question 22

Simple molecular oxides

Answer 22

P4O10 (s), SO2(g), SO3(g) are simple molecular with weak intermolecular forces between molecules (van der waals + permanent dipoles) so have lower mp’s.

Question 23

Sodium Oxide with water (pH and equation)

Answer 23

Na2O (s) + H2O (l) –> 2Na+(aq) + 2OH-(aq)
pH 13

Question 24

Magnesium Oxide with water (pH and equation)

Answer 24

MgO (s) + H2O (l)–> Mg(OH)2(s)
Product will form white precipitate as sparingly soluble
pH 9

Question 25

Al2O3 or SiO2 with water and pH

Answer 25

Al2O3 and SiO2 do not dissolve in water because of the high strength of the Al2O3 ionic lattice and the SiO2 macromolecular structure, so they give a neutral pH 7

Question 26

Acid base reactions - how does Al2O3 react? Equations?

Answer 26

Aluminium oxide can act as both an acid and an alkali and is therefore called amphoteric Aluminum oxide acting as a base: Al2O3 (s)+ 3H2SO4 (aq)--> Al2(SO4)3 (aq) + 3H2O (l) Al2O3 + 6HCl --> 2AlCl3 + 3H2O Or ionic: Al2O3 + 6H+ --> 2Al3+ + 3H2O Aluminum oxide acting as an acid Al2O3 (s)+ 2NaOH (aq) + 3H2O (l) --> 2NaAl(OH)4(aq) (this equation needs learning carefully) Al2O3 (s)+ 2OH- (aq) + 3H2O (l) --> 2Al(OH)4- (aq)

Question 27

What do the simple molecular period 3 oxides make when reacting with water?

Answer 27

Acids

Question 28

What's the trend in the reactions of the period 3 oxides with water?

Answer 28

The trend is the ionic metal oxides show basic behaviour and the non-metal covalent oxides show acidic behaviour. The slightly intermediate nature of the bonding in aluminium oxide is reflected in its amphoteric behaviour: it can act as both a base and an acid

Question 29

Phosphorus oxide + water and pH

Answer 29

P4O10(s) + 6 H2O (l)--> 4 H3PO4(aq) pH 0

Question 30

Sulfur dioxide with water and pH

Answer 30

SO2(g) + H2O (l)-->H2SO3(aq) pH 3 (weak acid)

Question 31

Sulfur trioxide with water and pH

Answer 31

SO3(g) + H2O (l)--> H2SO4(aq) pH 0

Question 32

Reactions of the basic oxides with acids

Answer 32

Na2O (s) + 2 HCl (aq)-->2NaCl (aq) + H2O (l) Na2O (s) + H2SO4(aq)-->Na2SO4(aq) + H2O (l) MgO (s) + 2 HCl (aq)-->MgCl2(aq) + H2O (l)

Question 33

Equations for the acidic oxides reacting with bases

Answer 33

P4O10(s) + 12 NaOH (aq)-->4Na3PO4(aq) + 6 H2O (l) P4O10+ 6 Na2O-->4Na3PO4 SO2(g) + 2NaOH (aq)-->Na2SO3(aq) + H2O (l) SO3(g) + 2NaOH(aq)-->Na2SO4(aq) + H2O (l)

Question 34

Macromolecular oxide reactions with base

Answer 34

2NaOH (l) + SiO2(s)--> Na2SiO3(aq) + H2O It is still classed as an acidic oxide

Question 35

Define amphoteric

Answer 35

Chemical can react as an acid or a base

Question 36

Displayed formula for phosphoric acid, sulfuric (IV) acid and sulfuric (VI) acid

Answer 36