2.4 Properties Of Period 3 Elements And Their Oxides Flashcards
Appearance and physical properties of sodium
Metallic, shiny, conducts electricity (worst conductor out of the metals)
Reaction of sodium with acid?
Na + acid —> H2 + salt
Reaction of sodium with cold water - equation and observations
Vigorous reaction, floats on water,fizzes melts due to -△H of the reaction. NaOH is pH 13-14.
2Na + 2H2O —> 2NaOH + H2
Reaction of sodium with oxygen (equation and observation)?
Bright yellow flame, forms white powder of Na2O
2Na + 1/2 O2 —> Na2O
Appearance and physical properties of magnesium
Metallic, shiny, conducts electricity (between Na and Al in terms of how well it does)
Reaction of Mg with cold water (observation and equation)
Very slow reaction. pH = 10 as Mg(OH)2 is sparingly soluble
Mg + 2H2O —> H2 + Mg(OH)2
Reaction of Mg with steam (observation and equation)? I’m
Much faster
Mg + H2O —> MgO + H2
Reaction of Mg with oxygen (observation and equation)?
Bright white flame, forms white powder of MgO
2!g + O2 —> 2MgO
Appearance and physical properties of aluminium?
Metallic, shiny best conductor of electricity in period 3
Reaction of Al with cold water?
No readtion
Reaction of Al with oxygen (observation and equation)?
Heat and lower into jar of O2–> bright flame, forms white powder
4Al + 3O2 —> 2Al2O3
Why is aluminium considered unreactive even through the metal itself is reactive
Covered by Al2O3 from where oxygen has oxidised the surface of the Al. Al2O3 is unreactive. Makes it useful for saucepans, window frames etc.
If Al2O3 is scratched off, Al reacts rapidly with air to form a new coat
Appearance and physical properties of silicon
Semimetal (metalloid), semiconductor (conducts electricity to an extent and in certain conditions)
Reaction of silicon with oxygen (observations and equations)?
Heat strongly
Si + O2 —> SiO2 (white powder)
Appearance and physical properties of phosphorus
Non-metal, low m.p. And b.p. Does not conduct electricity
Red phosphorus as a crystal structure
White phosphorus as P4
Reaction of phosphorus in excess oxygen (observations and equations)?
Red P needs to be heated significantly first, white P ignites spontaneously in air
Phosphorus pentoxide (white crystalline solid) formed
4P + 5O2 —> P4O10
Reaction of phosphorus in limited oxygen (observations and equation)?
Incomplete combustion: colourless liquid phosphorus trioxide s formed
4P + 3O2 —> P4O6
Appearance and physical properties of sulfur?
Non-metal, low mp and bp, does not conduct electricity
Reaction of sulfur with oxygen (observations and equation)?
Need to heat and lower into a jar of oxygen. Colourless gas sulfur dioxide formed. Some SO3 also formed.
S+O2–> SO2
What are the different types of structure and bonding displayed by the period 3 oxides?
Na ionic lattice
Mg ionic lattice
Al ionic lattice with covalent character; Al3+ distorts O2- electron cloud
Si giant covalent
P simple molecular covalent
S simple molecular covalent
What is the trend in melting points for period 3 oxides (state highest and lowest and why and draw graph)?
Slide 44
Which period 3 oxides are basic
Na2O and MgO
Reaction of Na oxide with water? pH?
Na2O + H2O —> 2Na+ + 2OH-; pH=14
Reaction of Mg oxide with water? pH?
MgO + H2O —> Mg2+ + 2OH- ⇌ Mg(OH)2
pH = 9-10 as Mg(OH)2 is sparingly soluble
What are the products if Na2O and MgO are reacted with acid?
Salt and water only
Is aluminium oxide acidic or basic
It is amphoteric; can act as either an acid or a base
Is aluminium oxide soluble
Not in water
Reaction of aluminium oxide with HCl?
Al2O3 + 6HCl —> 3H2O + 2AlCl3
Reaction of aluminium oxide with NaOH?
Al2O3 + 2NaOH + 3H2O —> 2NaAl(OH)4 ; sodium aluminate is formed
Is silicon dioxide soluble in water
No
In what conditions will silicon dioxide act as an acid
Reacts as a weak acid with a strong base
Reaction of silicon dioxide with hot, conc NaOH?
SiO2 + 2NaOH —> H2O + Na2SiO3 - sodium silicate
How is silicon dioxide used in the production of Fe?
SiO2 + CaO —> CaSiO3 - calcium silicate
Reaction of phosphorus pentoxide with water? pH?
P4O10 + 6H2O —> 4H3PO4; pH = 1-2
Dissociation of the acid formed (H3PO4)?
H3PO4 —> H+ + H2PO4-
Reaction of P4O10 with NaOH?
3NaOH + H3PO4 —> Na3PO4 + 3H2O
Reaction of SO2 with water? pH?
SO2 + H2O —> H2SO3 ; weak acid —> pH = 2-3
Reaction of SO3 with water? pH?
SO3 + H2O —> H2SO4
strong acid —> pH = 0-1
Reaction of SO2 with NaOH? (2 stages)
SO2 + NaOH —> NaHSO3
NaHSO3 + NaOH —> Na2SO3 + H2O
How can flue gases be removed by CaO?
CaO + SO2 —> CaSO3 (calcium sulfite)
Draw the structure of H3PO4?
Slide 84
How many electrons does P have in its outer shell in H3PO4?
10
What is the shape and bonding in PO43-?
Electrons delocalise to give tetrahedral structure with 109.5 bond angle. Each P-O bond is the same length
Draw the structure and bonding of H2SO4?
Slide 90
What is the structure, bonding and shape of SO4 2-?
Electrons delocalise —> tetrahedral with 109.5 bond angle. Each S-O bond is the same
What is the structure, bonding and shape of SO3 2-?
Bond angle = 106 (Trigonal pyramid shape), each S-O bond is the same, S has one lone pair of electrons
Uses of MgO
Additive for cattle feed
How useful is Al2O3?
Oxide layer on Aluminium makes it very useful as it is unreactive and returns quickly if it is scratched off
Uses of SO2
Reactant in contact process (making H2SO4)
Would lithium oxide or sodium oxide have a higher melting point? Why?
Li2O has a higher m.p., since Li+ is a smaller ion than Na+, so the O2- and Li+ charge centres are closer together and there is a greater electrostatic force of attraction between the oppositely charged ions