Reactions Of Ions In Aqeuous Solutions Flashcards
In aqueous solutions what ions are formed with
Fe^2+
Cu^2+
Al^3+
Fe^3+
[Fe(H2O)6]^2+
[Cu(H2O)6]^2+
[Al(H2O)6]^3+
[Fe(H2O)6]^3+
Explain when aqueous ions of [M(H2O)6]^3+ have a higher acidity that [M(H2O)6]^2+
This is because M^3+ ion complexes are larger and have a higher charge therefore having a stronger polarising power.
This means that the oxygen atoms in the water ligands are more strongly attracted to the M^3+ ions.
This therefore weakens the OH bonds meaning H+ ions are lost more easily and hence the solution is more acidic.
Define amphoteric?
A species that shows both acidic and basic properties
Explain the amphoteric properties of Aluminium hydroxide.
Although aluminium hydroxide is not a transition metal, it forms aqua ions.
With acid (HCL):
[Al(H2O)3(OH)3] + 3HCl ——> [Al(H2O)6]^3+ + 3Cl^-
With base (NaOH):
[Al(H2O)3(OH)3] + OH^- ——> [Al(OH)4]^- + 3H2O
Describe and explain (using equations) what happens when aqueous solution of [Fe(H2O)6]^2+ has the addition of
NaOH
NaOH (excess)
NH3
NH3 (excess)
Na2CO3
NaOH:
[Fe(H2O)6]^2 + NaOH ——> Fe(H2O)4(OH)2
Goes from green solution to form a dark green ppt which goes brown when standing in air
NaOH (excess):
No further change
NH3:
[Fe(H2O)6]^2 + NH3 ——> Fe(H2O)4(OH)2
Goes from green solution to form a dark green ppt which goes brown when standing in air
NN3 (excess):
No further change
Na2CO3:
[Fe(H2O)6]^2 + Na2CO3 ——> FeCO3
Goes from green solution to form a light green ppt
Describe and explain (using equations) what happens when aqueous solution [Cu(H2O)6]^2+ has the addition of
NaOH
NaOH (excess)
NH3
NH3 (excess)
Na2CO3
HCl
NaOH:
[Cu(H2O)6]^2+ + NaOH ——> [Cu(H2O)4(OH)2]^2+
Goes from dark blue solution to form a light blue ppt
NaOH (excess):
No further change
NH3:
[Cu(H2O)6]^2+ + 2NH3 ——> [Cu(H2O)4(OH)2]+ + 2NH4^+
Goes from a dark blue solution to a light blue ppt
NH3 (excess):
[Cu(H2O)4(OH)2]^2+ + 4NH3 ——> [Cu(NH3)4(H2O)2]^2+ + 4H2O
Goes from blue solution to a deep blue solution
Na2CO3:
[Cu(H2O)6]^2+ Na2CO3 ——> CuCO3
Goes from a blue solution to a blue-green ppt
HCl:
[Cu(H2O)6]^2 +HCl ——> [Cu(Cl)4]^2-
Goes form a blue solution to form a yellow solution
Describe and explain (using equations) what happens when aqueous solution [Fe(H2O)6]^3+ has the addition of
NaOH
NaOH (excess)
NH3
NH3 (excess)
Na2CO3
NaOH:
[Fe(H2O)6]^3+ + NaOH ——> [Fe(H2O)3(OH)3]
Goes from a purple solution to a brown ppt
NaOH (excess):
No further change
NH3:
[Fe(H2O)6]^3+ + NH3 ——> [Fe(H2O)3(OH)3]
Goes from a purple solution to a brown ppt
NH3 (excess):
No further change
Na2CO3:
[Fe(H2O)6]^3+ + Na2CO3 ——> [Fe(H2O)3(OH)3]
Goes from a purple solution to a brown ppt and CO2 gas evolved
Describe and explain (using equations) what happens when aqueous solution [Al(H2O)6]^3+ has the addition of
NaOH
NaOH (excess)
NH3
NH3 (excess)
Na2CO3
NaOH:
[Al(H2O)6]^3+ + NaOH ——> [Al(H2O)3(OH)3]
Goes from a colourless solution to a white ppt
NaOH (excess):
[Al(H2O)3(OH)3] + NaOH ——> [Al(OH)4]^-
Forms a colourless solution
NH3:
[Al(H2O)6]^3+ + NH3 ——> [Al(H2O)(OH)3]
Goes from a colourless solution to form a white ppt
NH3 (excess):
No further change
Na2CO3:
[Al(H2O)6]^3+ + Na2CO3 ——> [Al(H2O)3(OH)3]
Goes from a colourless solution to form a white ppt and CO2 has evolved
Describe and explain (using equations) what happens when aqueous solution [Co(H2O)6]^2+ has the addition of
NaOH
NH3 (excess)
Na2CO3
HCl
NaOH:
[Co(H2O)6]^2+ + NaOH ——> [Co(H2O)4(OH)2]
Goes from a pink solution to form a blue ppt
NH3 (excess):
[Co(H2O)6]^2+ + NH3 ——> [Co(NH3)6]^2+
Goes from a pink solution to form a pale brown solution
Na2CO3:
[Co(H2O)6]^2+ + Na2CO3 ——> CoCO3
Goes from a pink solution to form a purple ppt
HCl:
[Co(H2O)6]^2+ + HCl ——> [Co(Cl)4]^2-
Goes from a pink solution to form a blue solution
What is the test for positive ions?
Look at precipitation reactions for positive transition metal ions.
Half full a test tube and add ammonia or NaOH drop by drop
Observe colour change of precipitates formed
Add excess for more information
What is the test for ammonium ions?
Ammonium ions react with NaOH to produce ammonia
NH4+ + OH- ——> NH3 + H2O
If distinctive smell is produced and damp red litmus paper then blue then solution has ammonium ions
How do you find negative ions?
Carry out 3 tests
- Carbonate test
- Sulphate test
- Halide test
Carries out in this order as the carbonates and sulphates may give positive tests for one another
How do you test for carbonate ions?
Add an aqueous acid to suspected solution and if CO2 has is produced the. Carbonate ions are present
Test gas by bubbling through lime water and if goes cloudy white then the gas is CO2
What do you test for sulphate ions?
Acidify test solution with HCl
Add a few drops of barium chloride to the solution
A white precipitate is formed if sulphate ions are present.
What is the test for halide ions?
Add dilute nitric acid and aqueous silver nitrate solution
A precipitate of silver halide ions will form if chloride bromide or iodide is present