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transition metal ions reactions Flashcards

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1
Q

State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Cu2+

A
  • [Cu(H2O)6]2+(aq) + 2OH-(aq) -> [Cu(OH)2(H2O)4] (s) + 2H2O (l)
  • pale blue solution to pale blue precipitate
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2
Q

State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Cu2+

A

[Cu(H2O)6]2+(aq) + 2NH3(aq) -> [Cu(OH)2(H2O)4] (s) + 2NH4+ (aq)

blue solution to pale blue ppt

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3
Q

State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Fe2+

A

[Fe(H2O)6]2+ (aq) + 2OH- (aq) -> [Fe(OH)2(H2O)4] (s) + 2H2O (l)

pale green solution to dark green precipitate

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4
Q

State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Fe2+

A

[Fe(H2O)6]2+ (aq) + 2NH3 (aq) -> [Fe(OH)2(H2O)4] (s) + 2NH4+ (aq)

pale green solution to dark green precipate

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5
Q

State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Fe3+

A

[Fe(H2O)6]3+ (aq) + 3OH- (aq) -> [Fe(OH)3(H2O)3] (s) + 3H2O (l)

yellow solution to orange/brown precipitate

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6
Q

State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Fe3+

A

[Fe(H2O)6]3+ (aq) + 3NH3 (aq) -> [Fe(OH)3(H2O)3] (s) + 3NH4+ (aq)

yellow solution to orange/brown precipitate

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7
Q

State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Mn2+

A

[Mn(H2O)6]2+ (aq) + 2OH-(aq) -> [Mn(Oh)2(H2O)4] (s) + 2H2O (l)

a pale pink solution to pale brown precipitate

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8
Q

State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Mn2+

A

[Mn(H2O)6]2+ (aq) + 2NH3-(aq) -> [Mn(Oh)2(H2O)4] (s) + 2NH4+ (aq)

a pale pink solution to pale brown precipitate

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9
Q

State the equation and colour change when some OH- (aq) is added dropwise to the aqueous solution of Cr3+

A

[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

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10
Q

State the equation and colour change when some NH3 (aq) is added dropwise to the aqueous solution of Cr3+

A

[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

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11
Q

State the equation (if any) when excess OH- is added to the precipitate of copper (II) hydroxide

A

insoluble in excess NaOH so there is no change

stays as [Cu(OH)2(H2O)4] (s) a pale blue precipate

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12
Q

State the equation (if any) when excess NH3 (aq) is added to the precipitate of copper (II) hydroxide

A

[Cu(OH)2(H2O)4] (s) forms [Cu(NH3)4(H2O)2]2+ (aq)

colour change from pale blue ppt to dark blue solution

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13
Q

State the equation (if any) when excess OH- is added to the precipitate of iron (II) hydroxide

A

insoluble in excess NaOH so there is no change

stays as [Fe(OH)2(H2O)4] (s) dark green ppt

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14
Q

State the equation (if any) when excess OH- is added to the precipitate of iron (II) hydroxide

A

insoluble in excess NH3 so there is no change

stays as [Fe(OH)2(H2O)4] (s) dark green ppt

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15
Q

State the equation (if any) when excess OH- is added to the precipitate of iron (III) hydroxide

A

insoluble in excess NaOH so there is no change

stays as [Fe(OH)3(H2O)3] (s) orange/brown ppt

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16
Q

State the equation (if any) when excess NH3 is added to the precipitate of iron (III) hydroxide

A

insoluble in excess NH3 so there is no change

stays as [Fe(OH)3(H2O)3] (s) orange/brown ppt

17
Q

State the equation (if any) when excess OH- is added to the precipitate of manganese (II) hydroxide

A

insoluble in excess NaOH no change

stays as [Mn(Oh)2(H2O)4] (s) pale brown ppt

18
Q

State the equation (if any) when excess NH3 is added to the precipitate of manganese (II) hydroxide

A

insoluble in excess NH3 no change

stays as [Mn(Oh)2(H2O)4] (s) pale brown ppt

19
Q

State the equation (if any) when excess OH- is added to the precipitate of chromium (III) hydroxide

A

[Cr(OH)3(H2O)3] (s) forms Cr(OH)6 3- (aq)

tuns from dark green ppt to dark green solution

20
Q

State the equation (if any) when excess NH3 is added to the precipitate of chromium (III) hydroxide

A

[Cr(OH)3(H2O)3] (s) forms Cr(NH3)6 3+ (aq)

turns from dark green ppt to purple solution

21
Q

MnO4-/Fe2+ –> Mn2+/Fe3+

A
  • purple (MnO4-) to pale pink (Mn2+)
  • in titrations it is so dilute that it is practically colourless
22
Q

I-/Fe3+ –> I2/Fe2+

A

orange brown (Fe3+) to brown (I2)

23
Q

name the 5 transition metal ions and their colours in solution

A

Cr 3+ = green
-
Fe 2+ = pale green
-
Fe 3+ = yellow
-
Mn 2+ = pale pink

24
Q

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

A

M X+ + xOH- -> M(OH)x

25
Q

what are the colours of the 5 transition metal hydroxide precipitates?

A

Cr(OH)3 = grey/green
-
Fe(OH)2 = green
-
Fe(OH)3 = orange/brown
-
Mn(OH)2 = light brown

26
Q

which metal hydroxides change colour on standing with air? give reason why

A
  • 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
27
Q

what reagents are used to reduce Fe3+ to Fe2+? what is the colour change

A
  • iodide ions I-
  • yellow to pale green
28
Q

what happens if Cl- ions are added to Cu2+ solution? give full complex equation

A
  • ligand substitution
  • colour change from blue to yellow

[Cu(H2O)6]2+ + 4Cl- -> [CuCl4]2- + 6H2O

29
Q

what reagents are used to oxidise Cr3+ to Cr2O7 2-? what is the colour change

A
  • warm hydrogen peroxide H2O2/OH-
  • green to orange
30
Q

what reagents are used to reduce Cu2+ to Cu+? what is the color change?

A
  • iodide ions I-
  • blue solution to off-white precipitate of CuI
31
Q

what happens to Cu+ in solution?

A

spontaneously disproportionates into Cu2+ and Cu(s)

32
Q

what happens to Cu+ in the solution?

A

spontaneously disproportionates into Cu2+ and Cu(s)

33
Q

list the hydroxide precipitates that react with excess aqueous ammonia

A
  1. Cr III
  2. Cu II
34
Q

list the hydroxide precipitates that react with excess NaOH

A
  1. Cr III

chemistry (37 decks)

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