Inorganic Chemistry for the Chemistry Olympiad — Practice

Question 1

State the shape of XeF4.

Accepted Answer

Square planar, with two lone pairs opposite each other.

Question 2

Show that Ni(CO)4 obeys the 18-electron rule.

Accepted Answer

Ni contributes 10 electrons and four CO give 8, so the total is 18.

Question 3

Give the bond orders of O2, O2+ and O2- and order their bond lengths.

Accepted Answer

2, 2.5 and 1.5, so the bond length order is O2+ < O2 < O2-.

Question 4

Find the spin-only moments of high-spin [Fe(H2O)6]3+ and low-spin [Fe(CN)6]3-.

Accepted Answer

High spin d5 has 5 unpaired electrons, mu = root 35 = 5.92 BM. Low spin has 1 unpaired electron, mu = root 3 = 1.73 BM.

Question 5

Why is the first ionisation energy of nitrogen higher than that of oxygen?

Accepted Answer

Nitrogen has a half-filled p subshell, which is extra stable, while oxygen's paired p electron is easier to remove.

Question 6

Explain why zirconium and hafnium have almost identical radii.

Accepted Answer

The 4f electrons poorly shield the nucleus, so the 5d elements contract and match the 4d elements in size. Zr and Hf therefore have nearly equal radii and similar chemistry.

Question 7

Why are most tetrahedral complexes high spin?

Accepted Answer

The tetrahedral splitting is only about 4/9 of the octahedral, which is usually smaller than the pairing energy, so electrons occupy all orbitals singly first.

Question 8

How many atoms are there in a face-centred cubic unit cell?

Accepted Answer

Four.

Practice — Inorganic Chemistry for the Chemistry Olympiad

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