IB Chemistry SL Structure 1: Models of the particulate nature of matter 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.

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Multiple choice Written

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Question 1

Multiple choiceMedium1 mark

A pure substance undergoes one change of state. The diagrams show its particles immediately before and after the change. Which named process describes the change?

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Answer: A. The close, regular arrangement before the change represents a solid; the widely separated particles after it represent a gas. The direction is solid → gas, which is sublimation.
B: reverses the direction: deposition is gas → solid.
C: identifies the initial solid but treats the final state as liquid; melting is solid → liquid.
D: identifies the final gas but assumes the initial state is liquid; vaporization is liquid → gas.
Remember: identify both states and the direction of change.

Question 2

Paper 2Easy5 marks

A sample of chlorine is modelled as containing only the two isotopes shown in Figure 1. Use the mass numbers as the isotope masses when calculating the relative atomic mass.

(a)

State the number of neutrons in ${}^{37}_{17}\mathrm{Cl}$

[1]

(b)

State where the electrons are found relative to the nucleus in a chlorine atom.

[1]

(c)

Explain why ${}^{35}_{17}\mathrm{Cl}$ and ${}^{37}_{17}\mathrm{Cl}$ are isotopes.

[1]

(d)

Using Figure 1, determine the relative atomic mass of the chlorine sample. Give your answer to 3 significant figures.

[2]

Question 3

Multiple choiceMedium1 mark

A gaseous element is excited, and its emitted light is observed as separate violet and red lines. Which interpretation accounts for both the lines and their colours?

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Answer: C. Each line corresponds to a photon emitted as an excited electron returns to a lower energy level. Violet light has a shorter wavelength and higher frequency than red light, so violet photons have greater energy.

A: confuses emission with absorption, which occurs as electrons move to higher energy levels.
B: identifies emission correctly but reverses the relative photon energies of red and violet light.
D: reverses the electron transition direction; emission occurs when electrons move to lower energy levels.

Remember: shorter wavelength means higher frequency and greater photon energy.

Question 4

Paper 2Medium5 marks

Figure 1 shows the structural formula of bromomethane. Use the periodic table where needed.

(a)

Identify the element labelled A and state the period in which it is found.

[2]

(b)

Calculate the maximum number of electrons in the main energy level corresponding to the period of A.

[1]

(c)

Using your answer to (b), determine how many more electrons this main energy level can hold than the main energy level corresponding to carbon in Figure 1.

[2]

Question 5

Multiple choiceEasy1 mark

A sample contains $0.0400\ \text{mol}$ of $\mathrm{O_2}$ molecules. What is the number of oxygen atoms in the sample? Use $N_\mathrm{A}=6.02\times10^{23}\ \text{mol}^{-1}$

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Answer: C. Each $\mathrm{O_2}$ molecule contains two oxygen atoms. Thus, $0.0400\times6.02\times10^{23}\times2=4.82\times10^{22}$ oxygen atoms.

A: uses $0.00400\ \text{mol}$ and counts $\mathrm{O_2}$ molecules rather than oxygen atoms.
B: counts $\mathrm{O_2}$ molecules but omits the two oxygen atoms in each molecule.
D: shifts the amount one place too high, using $0.400\ \text{mol}$

Remember: multiply by the number of specified entities in each molecule when counting atoms.

Question 6

Multiple choiceMedium1 mark

A fixed amount of an ideal gas is heated from 300 K to 600 K while its pressure increases from 1.0 × 10⁵ Pa to 2.0 × 10⁵ Pa. What happens to its volume and molar volume?

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Answer: B. The molar volume is $V/n = RT/P$ Both $T$ and $P$ double, so $T/P$ and the molar volume remain unchanged; with the amount fixed, the volume also remains unchanged.
A: considers the pressure increase but ignores the effect of the doubled temperature.
C: considers the temperature increase but ignores the effect of the doubled pressure.
D: multiplies the temperature and pressure factors instead of using their ratio.
Remember: at fixed amount, volume changes in the same proportion as molar volume.

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