transition metal ions reactions Flashcards
State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Cu2+
- [Cu(H2O)6]2+(aq) + 2OH-(aq) -> [Cu(OH)2(H2O)4] (s) + 2H2O (l)
- pale blue solution to pale blue precipitate
State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Cu2+
[Cu(H2O)6]2+(aq) + 2NH3(aq) -> [Cu(OH)2(H2O)4] (s) + 2NH4+ (aq)
blue solution to pale blue ppt
State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Fe2+
[Fe(H2O)6]2+ (aq) + 2OH- (aq) -> [Fe(OH)2(H2O)4] (s) + 2H2O (l)
pale green solution to dark green precipitate
State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Fe2+
[Fe(H2O)6]2+ (aq) + 2NH3 (aq) -> [Fe(OH)2(H2O)4] (s) + 2NH4+ (aq)
pale green solution to dark green precipate
State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Fe3+
[Fe(H2O)6]3+ (aq) + 3OH- (aq) -> [Fe(OH)3(H2O)3] (s) + 3H2O (l)
yellow solution to orange/brown precipitate
State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Fe3+
[Fe(H2O)6]3+ (aq) + 3NH3 (aq) -> [Fe(OH)3(H2O)3] (s) + 3NH4+ (aq)
yellow solution to orange/brown precipitate
State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Mn2+
[Mn(H2O)6]2+ (aq) + 2OH-(aq) -> [Mn(Oh)2(H2O)4] (s) + 2H2O (l)
a pale pink solution to pale brown precipitate
State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Mn2+
[Mn(H2O)6]2+ (aq) + 2NH3-(aq) -> [Mn(Oh)2(H2O)4] (s) + 2NH4+ (aq)
a pale pink solution to pale brown precipitate
State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Cr3+
[Cr(H2O)6]3+ (aq) + 3OH-(aq) -> [Cr(OH)3(H2O)3] (s) + 3H2O (l)
pale purple (if heated turns green) solution to dark green precipitate
State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Cr3+
[Cr(H2O)6]3+ (aq) + 3NH3(aq) -> [Cr(OH)3(H2O)3] (s) + 3NH4+ (aq)
pale purple (if heated turns green) solution to dark green precipitate
State the equation (if any) when excess OH- is added to the precipitate of copper (II) hydroxide
insoluble in excess NaOH so there is no change
stays as [Cu(OH)2(H2O)4] (s) a pale blue precipate
State the equation (if any) when excess NH3 (aq) is added to the precipitate of copper (II) hydroxide
[Cu(OH)2(H2O)4] (s) forms [Cu(NH3)4(H2O)2]2+ (aq)
colour change from pale blue ppt to dark blue solution
State the equation (if any) when excess OH- is added to the precipitate of iron (II) hydroxide
insoluble in excess NaOH so there is no change
stays as [Fe(OH)2(H2O)4] (s) dark green ppt
State the equation (if any) when excess OH- is added to the precipitate of iron (II) hydroxide
insoluble in excess NH3 so there is no change
stays as [Fe(OH)2(H2O)4] (s) dark green ppt
State the equation (if any) when excess OH- is added to the precipitate of iron (III) hydroxide
insoluble in excess NaOH so there is no change
stays as [Fe(OH)3(H2O)3] (s) orange/brown ppt
State the equation (if any) when excess NH3 is added to the precipitate of iron (III) hydroxide
insoluble in excess NH3 so there is no change
stays as [Fe(OH)3(H2O)3] (s) orange/brown ppt
State the equation (if any) when excess OH- is added to the precipitate of manganese (II) hydroxide
insoluble in excess NaOH no change
stays as [Mn(Oh)2(H2O)4] (s) pale brown ppt
State the equation (if any) when excess NH3 is added to the precipitate of manganese (II) hydroxide
insoluble in excess NH3 no change
stays as [Mn(Oh)2(H2O)4] (s) pale brown ppt
State the equation (if any) when excess OH- is added to the precipitate of chromium (III) hydroxide
[Cr(OH)3(H2O)3] (s) forms Cr(OH)6 3- (aq)
tuns from dark green ppt to dark green solution
State the equation (if any) when excess NH3 is added to the precipitate of chromium (III) hydroxide
[Cr(OH)3(H2O)3] (s) forms Cr(NH3)6 3+ (aq)
turns from dark green ppt to purple solution
MnO4-/Fe2+ –> Mn2+/Fe3+
- purple (MnO4-) to pale pink (Mn2+)
- in titrations it is so dilute that it is practically colourless
I-/Fe3+ –> I2/Fe2+
orange brown (Fe3+) to brown (I2)
name the 5 transition metal ions and their colours in solution
Cr 3+ = green
-
Fe 2+ = pale green
-
Fe 3+ = yellow
-
Mn 2+ = pale pink
what is the pattern for ionic equations of transition metal reactions with OH- ions? use M as for the metal and x for the charge
M X+ + xOH- -> M(OH)x
what are the colours of the 5 transition metal hydroxide precipitates?
Cr(OH)3 = grey/green
-
Fe(OH)2 = green
-
Fe(OH)3 = orange/brown
-
Mn(OH)2 = light brown
which metal hydroxides change colour on standing with air? give reason why
- Fe(OH)2 turns from green to orange/brown at the surface as Fe2+ oxidises to Fe3+
- Mn(OH)2 darkens on standing with air
what reagents are used to reduce Fe3+ to Fe2+? what is the colour change
- iodide ions I-
- yellow to pale green
what happens if Cl- ions are added to Cu2+ solution? give full complex equation
- ligand substitution
- colour change from blue to yellow
[Cu(H2O)6]2+ + 4Cl- -> [CuCl4]2- + 6H2O
what reagents are used to oxidise Cr3+ to Cr2O7 2-? what is the colour change
- warm hydrogen peroxide H2O2/OH-
- green to orange
what reagents are used to reduce Cu2+ to Cu+? what is the color change?
- iodide ions I-
- blue solution to off-white precipitate of CuI
what happens to Cu+ in solution?
spontaneously disproportionates into Cu2+ and Cu(s)
what happens to Cu+ in the solution?
spontaneously disproportionates into Cu2+ and Cu(s)
list the hydroxide precipitates that react with excess aqueous ammonia
- Cr III
- Cu II
list the hydroxide precipitates that react with excess NaOH
- Cr III
