2.6 Reactions of ions in aqueous solution Flashcards
What happens when Fe2+ reacts with dilute sulphuric acid
- state observation
- state complex ion formed
observation : pale green solution
formula : {Fe(H2O)6}^2+
state formula of precipitate and observation when {Fe(H2O)6}^2+ is added to sodium hydroxide
- write equation
observation : green solution turns into a pale green precipitate
formula : Fe(OH)2(H2O)4
equation: Fe(H2O)6]2+ + 2OH- → Fe(H2O)4(OH)2 + 2H2O
state formula of precipitate and observation when Fe(OH)2(H2O)4 is allowed to stand in air
observation : brown precipitate
formula : Fe(OH)3(H2O)3
what happens when Cu^2+ dissolves in nitric acid
- state observation
- state formula
- write equation
observation : blue solution formed
formula : [Cu(H2O)6]2+
what happens when excess concentrated hydrochloric acid is added to [Cu(H2O)6]2+
- state formula
- state observation
- state equation
observation : yellow - green solution
formula : CuCl4^2-
equation : [Cu(H2O)6]2+ + 4Cl^- -> CuCl4^2- + 6H2O
what happens when aqueous ammonia is added to [Cu(H2O)6]2+
- state formula
- state observation
- write an equation for its formation
b) do the same for when an excess ammonia is added to the new ion
observation : blue precipitate
formula : Cu(OH)2(H2O)4
equation : Cu(H2O)6 ^2+ + 2NH3 -> Cu(OH)2(H2O)4 + 2NH4^+
b) formula : [Cu(NH3)4(H2O)2]^2+
observation : dark/deep blue solution
equation : Cu(H2O)4(OH)2 + 4NH3 -> Cu(NH3)4(H2O)^2+ 2H2O + 2OH^-
what happens when Na2CO3 is added to [Cu(H2O)6]2+ (aq)
- state formula
- state observation
- write an equation for its formation
formula : CuCO3
green precipitate
[Cu(H2O)6]^2+ + CO3^2- -> CuCO3 + 6H2O
Copper metal can be extracted from dilute aqueous solution containing copper (ii) ions using scrap ion
- state initial and final colour
- write an equation for its formation
initial : blue
final : green
equation : Cu^2+ (aq) + Fe(s) -> Cu (s) + Fe^2+ (aq)
what happens when Na2CO3 is added to [Fe(H2O)6]3+ (aq)
- state initial colour and final observation
- write an equation for its formation
brown solution gives a brown precipitate
effervescence
2[Fe(H2O)6]3+ + 3CO3^2– → 2Fe(H2O)3(OH)3 + 3CO2 + 3H2
what happens when Na2CO3 is added to [Al(H2O)6]3+ (aq)
- state observation
- write an equation for its formation
white precipitate
effervescence
2[Al(H2O)6]^3+ + 3CO3^2- -> 2[Al(H2O)3(OH)3] + 3CO2 + 3H2O
what happens when Na2CO3 is added to [Fe(H2O)6]2+ (aq)
- state initial colour and final observation
- write an equation for its formation
green solution gives a green precipitate
[Fe(H2O)6]2+ + CO32− → FeCO3 + 6H2O
what happens when excess concentrated HCl is added to [Co(H2O)6]^2+
- state initial colour and final observation
- write an equation for its formation
pink solution turns into a brown solution
[Co(H2O)6]2+ + 4Cl− → [CoCl4]^2− + 6H2O
what happens when dilute aqueous ammonia is added to [Al(H2O)6]3+ (aq)
- state observation
- write an equation for its formation
colourless solution gives a white precipitate
[Al(H2O)6]3+ + 3NH3 → Al(H2O)3(OH)3 + 3NH4
what happens when dilute aqueous ammonia is added to [Ag(H2O)2]^+
- state observation
- write an equation for its formation
no visible change as colourless solution remains a colourless solution
[Ag(H2O)2]+ + 2NH3 → [Ag(NH3)2]+ + 2H2
what forms with NaOH and Na2CO3 to form a white precipitate
Calcium & magnesium
What is formed when aluminium reacts with NaOH and Na2CO3
NaOH : white precipitate, dissolves in NaOH
Na2CO3 : white precipitate, bubbles of gas
An aqueous solution of Y gave a cream precipitate of Compound A when reacted with silver nitrate solution
Compound A gave a colourless solution when reacted with concentrated ammonia solution
Identify A
Silver bromide
Aqueous solution of Y gave a green precipitate B when reacted with sodium carbonate
- Identify B & write the simplest ionic equation that occurs when green precipitate B and sulfuric acid react
green precipitate of B was filtered and dried and then reacted with sulfuric acid to give a pale green solution containing compound C and a colourless gas D
Identify C and D
B: FeCO3 Iron (ii) carbonate
equation : 2H+ + CO3^2- -> H2O + CO2
C: Iron (ii) sulphate FeSO4
D: CO2
Solution A contains the compound [Cu(H2O)6]Cl2
State the type of bonding between the oxygen and hydrogen in this compound.
b) state why chloride ions in this compound are not considered to be ligands
Covalent bonding
b) they are not donating a lone pair to the metal ion
and it doesn’t form a coordinate bond to the metal ion
what is a complex ion
A complex ion is a positive metal ion surrounded by ligands. The ligands bond to the central metal ion by co-ordinate bonds
define a coordinate bond
a coordinate bond is a shared pair of electrons which have both come from the same atom
define a ligand
A Ligand is an ion or molecule with a lone pair of electrons which can form a coordinate bond with a metal ion
what is the coordination number
the number of coordinate bonds a transition metal ion forms
what happens when an excess of ammonia is added to [Cu(H2O)6]Cl2
- state observation
- write an equation for its formation
Cu(H2O)4(OH)2 + 4NH3 -> Cu(NH3)4(H2O)^2+ 2H2O + 2OH^-
deep blue solution formed
When anhydrous aluminium chloride reacts with water, solution Y is formed that contains a complex aluminium ion, Z, and chloride ions.
Give an equation for this reaction.
b) Give an equation to show how the complex ion Z can act as a Brønsted–Lowry acid with water.
AlCl3 + 6H2O -> [Al(H2O)6]^3+ + 3Cl
b) [Al(H2O)6]^3+ + H2O -> [Al(H2O)5(OH)]2+ + H2O^-
state the colour of a) [Cu(H2O)6]2+
b) [Fe(H2O)6]2+
c) [Fe(H2O)6]3+
d) [Al(H2O)6]3
a) Blue solution Pale
b) green solution
c) Yellow brown solution
d) Colourless solution
write equation of Fe(III) complex acting as an acid
Fe(H2O)6]3+ → [Fe(H2O)5(OH)]2+ + H+
Aqueous potassium hydroxide is added, until in excess, to [Al(H2O)6]^3+
Describe two observations you would make.
For each observation give an equation for the reaction that occurs.
Observation 1 : colourless solution to white precipitate
equation 1 : Al(H2O)6]3+ + 3OH- → Al(H2O)3(OH)3 + 3H2O
observation 2: White precipitate dissolves to form a colourless solution
equation 2 : Al(H2O)3(OH)3 + OH- → [Al(H2O)2(OH)4]- + H2O
state what is observed and give equation for when [Fe(H2O)6]^2+ reacts with Na2CO3
Observation : green solution to green precipitate
equation : Fe(H2O)6]2+ + CO32- → FeCO3(s) + 6H2O
state what is observed and give equation for when [Fe(H2O)6]^2+ reacts with NH3
Observation : green solution turns into green precipitate
equation : [Fe(H2O)6]2+ + 2NH3 → Fe(H2O)4(OH)2 + 2NH4+
reagent to turn [Fe(H2O)6]^3+ -> [Fe(H2O)6]^2+
Excess H2SO4
why, with use of an equation., a solution containing [Al(H2O)6]^3+ has a pH less than 7
Al(H2O)6]3+ ⇌ [Al(H2O)5(OH)]2+ + H+
Al3+ has a small size and high charge
Weakens the OH bond (in water) releasing H+ ions
Explain why an aqueous solution containing [Fe(H2O)6]3+ ions has a lower pH than an aqueous solution containing [Fe(H2O)6]2+ ions.
- [Fe(H2O)6]^3+ has a higher charge and is smaller
- Fe^3+ is more polarising as it polarises water molecules more
- more OH bonds in the water ligands break and hence more OH^+ ions are released
When anhydrous aluminium sulphate, Al2(SO4)3, is added to water a solution forms that contains the complex aluminium ion, [Al(H2O)6]3+Give the equation for the reaction
Al2(SO4)3 + 12 H2O → 2 [Al(H2O)6]3+ + 3 SO42-
Explain why the solution containing [Al(H2O)6]3+ is acidic
Al3+ has a high charge and small size
Al3+ weakens the O-H bond (in water ligands and donates H+ to water or forms H3O+ ions with water
Which aqueous-ion solutions are the most acidic
[Fe(H20)6]^3+ & [Al(H20)]^3+
Why are solutions of [Al(H2O)6]3+ and [Fe(H2O)6]3+ more acidic than solutions of [CuH2O)6]2+ and [Fe(H2O)6]2+?
Al3+ and Fe3+ are smaller and have a higher charge than Cu2+ and Fe2+. Al3+ and Fe3+ polarise the water ligands more than Cu2+ and Fe2+, so the weaken the O−H bonds more (and dissociate more H+)
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