IB Chemistry HL Structure 1: Models of the particulate nature of matter questions

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Multiple choice Written

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Question 1

Paper 2Medium6 marks

A laboratory has several batches of a dry solid containing crystalline sulfur and sodium chloride. The relative amounts of the two substances vary between batches. Sodium chloride dissolves in water, whereas sulfur does not. A student wants to obtain dry sodium chloride from one batch.

(a)

Classify each of sulfur and sodium chloride as an element, compound or mixture.

[2]

(b)

State one feature, other than the variable proportions, that distinguishes this sample from a compound.

[1]

(c)

Outline a sequence of steps to obtain dry sodium chloride from the sample.

[3]

Question 2

Paper 2Easy5 marks

Methanol with an isotopically labelled carbon atom is shown in Figure 1. The superscript gives the mass number of the labelled atom.

(a)

Use the isotope label in Figure 1 and the periodic table to determine the numbers of protons and neutrons in the labelled atom’s nucleus.

[2]

(b)

For a neutral atom of this isotope, state the number of electrons, the charge of its nucleus, and where its electrons are located relative to the nucleus.

[3]

Question 3

Paper 2Medium10 marks

A representative sample of natural boron is characterized for use in a neutron-absorbing material. It contains the isotopes ¹⁰₅B and ¹¹₅B. The relative isotopic masses and relative atomic mass of the sample are:

Isotope	Relative isotopic mass
¹⁰₅B	10.0129
¹¹₅B	11.0093

The relative atomic mass, Aᵣ, of the sample is 10.811.

(a)

For the ion ¹⁰₅B⁺, state the number of protons, neutrons and electrons.

[3]

(b)

Explain why ¹⁰₅B and ¹¹₅B are isotopes.

[2]

(c)

Assuming the sample contains only these two isotopes, determine the percentage abundance of ¹⁰₅B. Give your answer to three significant figures.

[3]

(d)

A student claims that ¹⁰₅B and ¹¹₅B must have identical physical properties because they have the same number of protons. Explain why this claim is not justified.

[2]

Question 4

Paper 2Easy5 marks

A student observes light from a hydrogen discharge tube using a spectroscope. Four emission lines are measured.

Wavelength / nm
656.3
486.1
434.0
410.2

(a)

State whether the spectrum consists of continuous or line emission.

[1]

(b)

State what happens to an electron when one of these photons is emitted.

[1]

(c)

Determine which photon, with wavelength 656.3 nm or 434.0 nm, has the greater energy. Justify your answer.

[2]

(d)

As the wavelength decreases through the values in the table, state how the spacing between successive spectral lines changes.

[1]

Question 5

Paper 2Medium7 marks

The wavelength corresponding to the limit of convergence at higher frequency in the emission spectrum of gaseous element Q is $285.7\ \mathrm{nm}$

A database gives the following successive ionization energies for Q.

Ionization energy	Value / $\mathrm{kJ\,mol^{-1}}$
First	419
Second	3052
Third	4420
Fourth	5877

(a)

Calculate the first ionization energy of Q in $\mathrm{kJ\,mol^{-1}}$ using the data booklet. Give your answer to three significant figures.

[3]

(b)

Use your result from (a) and the successive ionization energy data.

(i)

State whether your result from (a) agrees with the database value for the first ionization energy to three significant figures.

[1]

(ii)

Deduce the group of Q, explaining your deduction using the successive ionization energy data.

[3]

Question 6

Paper 2Medium8 marks

A quality-control test estimates the hydrogen peroxide concentration in a solution labelled 10.0 g dm⁻³. A 10.00 cm³ sample is completely decomposed according to the equation:

2 H₂O₂(aq) → 2 H₂O(l) + O₂(g)

The oxygen produced has a volume of 36.0 cm³. A 25.0 cm³ sample of nitrogen at the same temperature and pressure contains 1.00 × 10⁻³ mol of nitrogen. Assume both gases behave ideally and that no oxygen is lost. Use M(H₂O₂) = 34.0 g mol⁻¹.

(a)

Determine the amount, in mol, of oxygen produced.

[2]

(b)

Calculate the molar concentration, [H₂O₂], in the original solution, in mol dm⁻³.

[3]

(c)

Calculate the mass concentration of hydrogen peroxide in the original solution, in g dm⁻³.

[1]

(d)

Using the labelled concentration as the reference, calculate the percentage by which your result in (c) differs from the label, and state whether the measured value is higher or lower.

[2]

Question 7

Paper 2Medium6 marks

A chemist compares equal amounts of gaseous nitrogen at two different sets of conditions. Figure 1 shows schematic particle diagrams for the samples.

(a)

State three assumptions of the ideal-gas model.

[3]

(b)

Using Figure 1, identify the sample expected to show the greater deviation from ideal-gas behaviour.

[1]

(c)

Using Figure 1 and your knowledge of the ideal-gas model, explain how the conditions for this sample favour deviation from ideal-gas behaviour.

[2]

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