pmt period 3 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 -ΔH of the reaction. NaOH is pH 13-14.
2Na + 2H2O → 2NaOH + H2
Reaction of sodium with oxygen (equation and observations)?
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 (observations 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 (observations and equation)?
Much faster.
Mg + H2O → MgO + H2
Reaction of Mg with oxygen (observations and equation)?
Bright white flame, forms white powder of MgO 2Mg + O2 → 2MgO
Appearance and physical properties of aluminium?
Metallic, shiny, best conductor of electricity in period 3
Reaction of Al with cold water?
No reaction
Reaction of Al with oxygen (equation and observations)?
Heat and lower into jar of O2 → bright flame, forms white powder.
4Al + 3O2 → 2Al2O3
Why is aluminium considered unreactive even though 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 equation)?
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 phosphorous in excess oxygen (observations and equation)?
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 phosphorous in limited oxygen
(observations and equation)?
Incomplete combustion: colourless liquid phosphorus trioxide is 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
Highest is MgO,lowest is SO2; increases along group for metals for Na2O and MgO due to stronger ionic bonding, but Al2O3 is lower due to the covalent character of the bonding. Decreases with size for simple molecular molecules.
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 (e.g. hot, conc NaOH)
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 oxide 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)
How many electrons does P have in its outer shell in H3PO4?
10
What is the shape and
bonding in PO4 3-?
Electrons delocalise to give tetrahedral structure with 109.5o bond angle. Each P-O bond is the same length
What is the structure, bonding and shape of SO4 2-?
Electrons delocalise → tetrahedral with 109.5o bond angle. Each S-O bond is the same
What is the structure, bonding and shape of
SO3 2-?
Bond angle = 106o (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.
