Properties of Period 3 elements/oxides Flashcards
State which period 3 elements react with water
- sodium
- magnesium
- chlorine
Describe reaction between sodium and water
2Na + 2H20 -> 2NaOH + H2
- metal skates on surface of water
- exothermic so sodium might ignite (burn orange flame)
- effervescence (hydrogen gas)
- forms strong alkaline solution
Describe reaction between magnesium and water at room temperature
Mg + 2H2O (l) -> Mg(OH)2 + H2
- slow reaction
- few bubbles (hydrogen gas) on surface of magnesium
- forms less alkaline solution since Mg(OH)2 is sparingly soluble
Describe reaction between magnesium and steam
Mg + H2O (g) -> MgO + H2
- white solid magnesium oxide
- hydrogen gas
Describe reaction between sodium and oxygen
- burns yellow flame
- white solid Na2O formed
Describe reaction between magnesium and oxygen
- burns bright white flame
- white solid MgO formed
Describe reaction between aluminium and oxygen
- burns bright white flame
- white solid Al2O3 formed
Describe reaction between silicon and oxygen
- white solid SiO2 formed (if heated strongly enough)
Describe reaction between (white) phosphorus and oxygen
P4 + 5O2 -> P4O10
- ignites spontaneously in air
- burns with white flame
- cloud of white smoke P4O10
Describe reaction between sulfur and oxygen
S + O2 -> SO2
(2SO2 + O2 -> 2SO3)
- burns with blue flame
- pungent SO2 fumes
State structure and bonding in highest oxides of elements Na-S
Na2O - giant ionic lattice/ionic
MgO - giant ionic/ionic
Al2O3 - giant ionic with covalent character
SiO2 - giant covalent (macromolecule)/covalent
SO3 - molecular covalent
Explain trend in melting points of highest oxides of the elements Na–S
- increases to highest (MgO) then decreases
- increase in charge density of Na+ compared to Mg2+ ion means stronger ionic bonding
- Al3+ has high charge density so distorts O2- so oxide has covalent character (irregular compared to lattice)
- many covalent bonds in SiO2
- P4O10 is larger molecule compared to SO3 so has stronger van der Waals
Describe reaction between Na2O and water
Na2O + H2O -> 2NaOH
- strong alkaline solution formed (pH around 14)
- exothermic
Describe reaction between MgO and water
MgO + H2O -> Mg(OH)2
- weak alkaline solution (pH around 9)
Describe reaction between Al2O3 and water
insoluble so no reaction (pH 7)
Describe reaction between SiO2 and water
insoluble so no reaction (pH 7)
Describe reaction between P4O10 and water
P4O10 + 6H2O -> 4H3PO4
- acidic solution formed (pH 1-2) NOT A WEAK ACID
Describe reaction between SO2 and water
SO2 + H2O -> H2SO3 (sulfurous acid)
- acidic solution formed (pH 2-3)
Describe reaction between SO3 and water
SO3 + H2O -> H2SO4 (sulfuric acid)
- acidic solution formed (0-1)
Give equation for reaction between Na2O and acid/alkali
acid - Na2O + 2H+ -> 2Na+ + H2O
alkali - none
nature of oxide = basic
Give equation for reaction between MgO and acid/alkali
acid - MgO + 2H+ -> Mg2+ + H2O
alkali - none
nature of oxide = basic
Give equation for reaction between Al2O3 and acid/alkali
acid - Al2O3 + 6H+ -> 2Al3+ + 3H2O
alkali - Al2O3 + 3H2O + 2OH- -> 2[Al(OH)4]-
nature of oxide = amphoteric
Give equation for reaction between P4O10 and acid/alkali
acid - none
alkali - P4O10 + 12OH- ->4PO43- + 6H2O
nature of oxide = acidic
(know P4O10 > PO43- then write out ionic equation and then replace H+ with OH-)
Give equation for reaction between SO2 and acid/alkali
acid - none
alkali - SO2 +2OH- -> SO32- H2O
nature of oxide = acidic
Give equation for reaction between SO3 and acid/alkali
acid - none
alkali - SO3 +2OH- -> SO42- H2O
nature of oxide = acidic
Suggest why period 3 metallic elements form basic oxides hence alkaline solutions in water
- metal oxides have ionic bonding so contain O2-
- O2- can accept H+ from water to form OH-
Suggest why Al2O3 and SiO2 do not react with water
- Al2O3 strong bonding due to covalent character
- SiO2 has giant covalent structure which is insoluble
Outline an experiment that could be used to show that aluminium oxide contains ions
- heat until molten (do not dissolve in water since insoluble)
- electrolyse and identify Al and O2 at electrodes
Explain the trend in reactions of Period 3 oxides with water and why MgO forms weaker solution than Na2O
- Na2O and MgO are basic so form hydroxides since they contain oxide ion which has a tendency to combine with H+
- Mg(OH)2 less soluble than NaOH so forms weaker alkaline solution
- Al2O3 does not react with water since oxide ion held too strongly in lattice
- SiO2 does not react with water since giant covalent structure is insoluble
- P4O10 and SO3 are acidic so form acids with water since they accept lone pair of electrons from oxygen on water
Give equation for reaction between SiO2 and acid/alkali
acid - none
base - SiO2 + 2OH- -> SiO32- + H2O
nature of oxide = weak acidic
Write equation for reaction between Na2O then MgO with P4O10 and state type of reaction
6Na2O + P4O10 -> 4Na3PO4
6MgO + P4O10 -> 2Mg3(PO4)2
acid-base reaction
(no need to write out half equations to show them behaving as acidic / basic - just know Na2O > Na+ and MgO > Mg2+ while P4O10 > PO43-)
State physical properties of SiO2
- insoluble
- non conductor
(high melting/boiling point might not score mark)
Write ionic equation and overall equation for reaction between Al2O3 and HCl then NaOH
ionic
Al2O3 + 6H+ -> 2Al3+ + 3H2O
Al2O3 + 3H2O + 2OH- -> 2[Al(OH)4]-
(reject HCl or NaOH; only allow Cl- or Na+ as spectator ions)
overall
Al2O3 + 6HCl -> 2AlCl3 + 3H2O
Al2O3 + 3H2O + 2NaOH -> 2Na[Al(OH)4]
Describe how to prove SiO2 is acidic
- react with NaOH
- neutralises base (pH7)
Explain why SiO2 is insoluble in water
- macromolecular
- many strong covalent bonds
- water cannot supply sufficient energy to break bonds
Problems with acid rain caused by SO2 and why removed SO2
- toxic breathing problems
- erodes buildings
- reduce waste
- produce H2SO4
