15B: Reactions of transition metal elements Flashcards

1
Q

State the colours of the oxidation states of vanadium (+5, +4, +3 and +2) in its compounds.

A

+5: Yellow (VO2+)
+4: Blue (VO2+
+3: Green (V3+)
+2: Violet (V2+)

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2
Q

Describe the reduction of the dichromate(VI) ion, Cr2O72−.

A

Reduced to Cr3+ and Cr2+ ions,
Using zinc in acidic conditions.

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3
Q

Describe a method to produce the dichromate(VI) ion, Cr2O72−.

A

Oxidation of Cr3+ ions,
Using hydrogen peroxide in alkaline conditions (followed by acidification).

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4
Q

Give the equilibrium equation that results in the conversion of the dichromate(VI) ion, Cr2O72−, into chromate(VI) ions.

A

2CrO42− + 2H+ ⇌ Cr2O72− + H2O

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5
Q

Write an ionic equation for the reaction of the complex ion, [M(H2O)x]y+, with aqueous sodium hydroxide, and state the type of reaction.

A

[M(H2O)x]y+ + yOH- → [M(H2O)x-y(OH)y] + yH2O

Proton transfer

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6
Q

Write an ionic equation for the reaction of the complex ion, [M(H2O)x]y+, with aqueous ammonia, and state the type of reaction.

A

[M(H2O)x]y+ + yNH3 → [M(H2O)x-y(OH)y] + yNH4+

Proton transfer

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7
Q

Define the term amphoteric

A

Can act as an acid or a base

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8
Q

Describe the difference between ligand exchange and amphoteric behaviour in terms of the reactions of aqueous complex ions with NaOH or NH3.

A

Amphoteric behaviour: H2O ligands are deprotonated by the base, so the complex ions acts as an acid.

Ligand exchange: NH3 ligands exchange with H2O ligands.

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9
Q

Reaction of aqeous copper(II) ions with concentrated hydrochloric acid:
Product,
Colour change,
Type of reaction.

A

[CuCl4]2-,
Blue -> green,
Ligand exchange.

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10
Q

Reaction of aqeous cobalt(II) ions with concentrated hydrochloric acid:
Product,
Colour change,
Type of reaction.

A

[CoCl4]2-,
Pink -> blue,
Ligand exchange.

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11
Q

Describe a reaction that can lead to a change in coordination number.

A

The substitution of small, uncharged ligands (such as H2O) by
larger, charged ligands (such as Cl).

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12
Q

Explain why the substitution of a monodentate ligand by a bidentate or multidentate ligand leads to a more stable complex ion.

A

The small ligands are released and have greater freedom of movement,
so there is a large positive increase in ΔSsystem.

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13
Q

Describe a heterogeneous catalyst

A

The catalyst is in a different phase from the reactants,
The reaction occurs at the surface of the catalyst.

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14
Q

Describe the contact process.

A

Converts oxygen and sulfur dioxide to sulfur trioxide.

Catalyst: V2O5

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15
Q

State the role of a catalytic converter

A

Decreases carbon monoxide and nitrogen monoxide emissions from internal combustion engines

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16
Q

Describe how a catalytic converter works

A
  • Adsorption of CO and NO molecules onto the surface of the catalyst,
  • Bonds are weakened so a chemical reaction can occur,
  • Desorption of CO2 and N2 product molecules from the surface of the catalyst.
17
Q

Describe a homogeneous catalyst

A

The catalyst is in the same phase as the reactants,
The catalysed reaction will proceed via an intermediate species.

18
Q

State the catalyst for the reaction between I and S2O82− ions

A

Fe2+ ions

19
Q

State the catalyst and the type of catalysis for the reaction between MnO4 and C2O42− ions

A

Mn2+ ions,
Autocatalysis