IB Chemistry HL 2.4 From Models to Materials Questions

Practise IB Chemistry HL 2.4 with evidence-led questions on energy, spontaneity, entropy, enthalpy and chemical reactions.

Exam points

Analyse compounds and materials using a bonding continuum rather than treating ionic, covalent and metallic descriptions as isolated types.
Use electronegativity and ion mobility to compare ionic character and conductivity in solid and molten materials.
Explain how alloy composition and atomic-size mismatch affect strength, hardness, conductivity and material choice.
Relate polymer structure, branching, cross-linking and intermolecular forces to properties, recycling and degradation.
Deduce monomers, repeating units and eliminated small molecules for addition and condensation polymers.

Covered syllabus points

2.4.1—Bonding continuum 2.4.2—Bonding triangle 2.4.3—Alloys 2.4.4—Polymers 2.4.5—Addition polymers 2.4.6 (HL)—Condensation polymers

[Maximum number: 3]

Iron may be extracted from iron (II) sulfide, FeS.

(a)

Iron (II) sulfide, FeS, is ionically bonded.

[ 1 ]

(i)

Suggest why chemists find it convenient to classify bonding into ionic, covalent and metallic.

[ 1 ]

(b)

Explain why the addition of small amounts of carbon to iron makes the metal harder.

[ 2 ]

[Maximum number: 2]

A sample of bromine has the following composition by mass:

\begin{array}{cc} { }^{79} \mathrm{Br}: & 50.75 \% \\ { }^{81} \mathrm{Br}: & 49.25 \% \end{array}

Deduce, showing your working, the type of bonding and percentage covalent character in calcium bromide, $\mathrm{CaBr}_{2}$ . Use sections 9 and 17 of the data booklet.

[Maximum number: 2]

Titanium and vanadium are consecutive elements in the first transition metal series.

Explain why an aluminium-titanium alloy is harder than pure aluminium.

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Covered syllabus points

Question 1

Question (a)

Question (i)

Question (b)

Question 2

Question 3