IB Chemistry SL Structure 2: Models of bonding and structure questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type

Multiple choice Written

Difficulty

Easy Medium Hard

Question 1

Paper 2Medium6 marks

Aluminium oxide is a hard material used in abrasive surfaces. An aluminium atom has electron configuration 2,8,3, and an oxygen atom has electron configuration 2,6. In forming ions in this compound, each atom attains a full outer energy level.

(a)

Deduce the ion formed by an aluminium atom, stating the number of electrons transferred.

[2]

(b)

Deduce the ion formed by an oxygen atom, stating the number of electrons transferred.

[2]

(c)

Use your answers to (a) and (b) to determine the simplest formula of aluminium oxide. Show how the charges determine the ratio of ions.

[2]

Question 2

Paper 2Medium4 marks

Figure 1 shows Lewis representations of ammonia, $\ce{NH3}$ and methane, $\ce{CH4}$ Each line represents a single covalent bond. The arrangements shown do not represent the three-dimensional molecular shapes.

(a)

State the electron-domain geometry around the central atom in each molecule.

[1]

(b)

Compare the molecular geometries of $\ce{NH3}$ and $\ce{CH4}$

[1]

(c)

The H–N–H bond angle in $\ce{NH3}$ is smaller than the H–C–H bond angle in $\ce{CH4}$ Explain why.

[2]

Question 3

Paper 2Hard12 marks

Three metals are compared using the simplified metallic model. Figure 1 shows formula-unit representations of their chlorides. The chloride-ion charges are shown, but the metal-ion charges are omitted. Table 1 gives the cation radii adopted for the model and the melting points of the pure metals at standard pressure. The students use melting point as evidence of the relative strength of metallic bonding.

Metal	Cation radius adopted in the model / pm	Melting point / °C
K	138	63.4
Na	102	97.8
Mg	72	650

(a)

Use Figure 1 to deduce the charge of the metal ion in each of the three compounds.

[3]

(b)

A student wants to examine the effect of cation radius on melting point while keeping cation charge constant. Identify the appropriate pair of metals, calculate the difference in their cation radii and melting points, and use the results to explain which metal has stronger metallic bonding according to the model.

[4]

(c)

Compare magnesium with sodium to explain their difference in melting points. Refer to both cation charge and radius.

[2]

(d)

A student concludes that the rise in melting point from sodium to magnesium is caused only by the increase in cation charge. Assess whether this conclusion is justified, using evidence from Figure 1 and Table 1.

[3]

Question 4

Paper 2Medium6 marks

Brass is an alloy of copper and zinc. It is generally harder than pure copper. Figure 1 shows schematic representations of two brass samples and the structure of polymer P.

(a)

Use Figure 1(a) to explain why brass is classified as a mixture rather than a compound.

[2]

(b)

Using Figure 1(a), explain how the structure of brass can account for its greater hardness than pure copper. Include the role of metallic bonding.

[2]

(c)

For polymer P in Figure 1(b), name the monomer and state the structural feature that identifies P as a polymer.

[2]

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