Developing Metals

Question 1

Why are Sc and Zn not considered transition metals?

Answer 1

When they form stable ions, the d orbitals is either empty or filled which defeats the definition of a transition metal.

Question 2

Why are Cr and Cu different in their electronic arrangement?

Answer 2

• The orbital energies are such that a lower total energy occurs when the d orbital is empty or filled
• Empty for Cr
• Filled for Cu

Question 3

Why can Transition metals exist in a number of oxidation states?

Answer 3

There are several stable arrangements of the d-electrons and the s-electrons.

Question 4

The Half-equations for the oxidation of Iron (II) to Iron (III) by potassium manganate (VII)

Answer 4

(Oxidations)
Fe^2+(aq) –> Fe^3+(aq) + e^-

(Reduction)
MnO4^-(aq) + 8H^+ + 5e^- –> Mn^2+ + 4H2O(l)

Question 5

End point of the Iron (II) titration by potassium manganate (VII)

Answer 5

When the first permanent pink colour is observed.

Question 6

Using acidified potassium dichromate instead of potassium manganate to determine conc. of Fe^2+ ions half equation

Answer 6

Cr2O7^2-(aq) + 14H^+ + 6e^- –> 2Cr ^3+(aq) + 7H20(l)

Question 7

What is a Catalyst?

Answer 7

A substance that increases the rate of a reaction by providing an alternate reaction pathway with a lower activation energy while not being used up in the reaction.

Question 8

Why are transition metals good catalysts?

Answer 8

The availability of the 3d and 4s electrons and the ability to change oxidation state.

Question 9

What is a heterogeneous catalyst?

Answer 9

A catalyst in a different phase or state from the reactants.
Usually a solid catalyst with the reactants in the liquid or gas phase.

Question 10

How does heterogeneous catalysis work?

Answer 10

• Transition metals use the 3d and 4s electrons on the metal surface to form weak bonds (chemisorption) to reactants.
• These bonds can break to release the products.

Question 11

What is a homogeneous catalyst?