Structure 1: Models of the particulate nature of matter

Convert every mass, volume and concentration to moles first, and keep cm³ and dm³ apart. A formula's subscripts are mole ratios.

A lesson for this part

Multiple choice, Paper 1A style

Question 1

A pure solid is heated at a constant rate. The graph shows its temperature against time, divided into sections P to T. In which section is the mean kinetic energy of the particles constant while the liquid changes into a gas?

Question 2

The temperature of a sample of gas is raised from 27 °C to 327 °C. By what factor does the average kinetic energy of its particles increase?

Question 3

A mixture contains sand, sodium chloride and water. Which method gives dry crystals of sodium chloride?

Question 4

A food colouring X and four pure dyes A, B, C and D are spotted on the baseline of chromatography paper, which is then placed in a solvent. The chromatogram is shown. Which dyes does X contain?

Question 5

Which is a homogeneous mixture?

Question 6

How many protons, neutrons and electrons are in one ³⁴S²⁻ ion?

Question 7

Which are the same for an atom of ³⁵Cl and an atom of ³⁷Cl? I. the number of protons II. the number of electrons III. the mass of the atom

Question 8

Isotopes of boron: ¹⁰B has a percentage abundance of 19.9%; ¹¹B has a percentage abundance of 80.1%.
Isotope	Percentage abundance / %
¹⁰B	19.9
¹¹B	80.1

The table gives the percentage abundances of the isotopes of boron. What is the relative atomic mass of boron?

Question 9

An element has two isotopes, of mass numbers 85 and 87, and a relative atomic mass of 85.47. What is the percentage abundance of the isotope of mass number 85?

Question 10 · HL

The mass spectrum of a sample of magnesium is shown, with each peak's abundance relative to the tallest peak. What is the relative atomic mass of magnesium in the sample?

Question 11 · HL

The mass spectrum of bromine atoms has two peaks, shown with their abundances relative to the tallest peak. What is the percentage abundance of ⁸¹Br?

Question 12 · HL

The mass spectrum of an element has two peaks, shown with their abundances relative to the tallest peak. Which element is it?

Question 13

What is the ground-state electron configuration of the Fe³⁺ ion?

Question 14

What is the ground-state electron configuration of a chromium atom?

Question 15

Proposed orbital diagram for nitrogen. 1s orbital: two electrons with opposite spins. 2s orbital: two electrons with opposite spins. First 2p orbital: two electrons with opposite spins. Second 2p orbital: one electron. Third 2p orbital: empty.
1s	2s	2p (first)	2p (second)	2p (third)
↑↓	↑↓	↑↓	↑	empty

The table shows a proposed arrangement of the seven electrons of a nitrogen atom in orbitals, with arrows for electron spins. Which statement about it is correct?

Question 16

Which electron transition in a hydrogen atom emits the line of highest frequency in the visible region, among these?

Question 17 · HL

The lines of the Lyman series in the emission spectrum of hydrogen converge at a wavelength of 91.2 nm. What is the first ionisation energy of hydrogen?

Question 18 · HL

The first ionisation energy of sodium is 496 kJ mol⁻¹. What is the minimum frequency of radiation that can ionise one gaseous sodium atom?

Question 19 · HL

Successive ionisation energies of X in kJ mol⁻¹: first 578, second 1817, third 2745, fourth 11 577, fifth 14 842.
Ionisation energy	first	second	third	fourth	fifth
Value / kJ mol⁻¹	578	1817	2745	11 577	14 842

The table gives the first five successive ionisation energies of an element X in period 3. In which group of the periodic table is X?

Question 20 · HL

The first ionisation energy of aluminium is lower than that of magnesium. Which statement explains this?

Question 21 · HL

The first ionisation energy of oxygen is lower than that of nitrogen. Which statement explains this?

Question 22 · HL

The bar chart shows the first ionisation energies of the period 2 elements. Which element's value is evidence that the 2p sublevel is higher in energy than the 2s sublevel?

Question 23 · HL

Which equation represents the second ionisation energy of magnesium?

Question 24 · HL

For which element is the first large jump in successive ionisation energies between the fourth and the fifth ionisation energies?

Question 25

How many hydrogen atoms are in 3.6 g of water?

Question 26

Percentage composition by mass of an oxide of iron: iron 69.9%, oxygen 30.1%.
Element	Percentage by mass / %
iron	69.9
oxygen	30.1

The table gives the percentage composition by mass of an oxide of iron. What is its empirical formula?

Question 27

Complete combustion of 0.290 g of a hydrocarbon produced 0.880 g of carbon dioxide and 0.450 g of water.
Substance	Mass / g
hydrocarbon burned	0.290
carbon dioxide formed	0.880
water formed	0.450

A sample of a hydrocarbon is burned completely in excess oxygen. The table gives the masses of the products. What is the empirical formula of the hydrocarbon?

Question 28

4.00 g of sodium hydroxide, NaOH, is dissolved in water and made up to 250 cm³ of solution. What is the concentration of the solution?

Question 29

What volume of water must be added to 25.0 cm³ of 2.00 mol dm⁻³ hydrochloric acid to dilute it to 0.100 mol dm⁻³?

Question 30

Two flasks of the same volume, at the same temperature and pressure, contain hydrogen, H₂, and carbon dioxide, CO₂. Which are the same for the two gases? I. the number of molecules II. the mass of gas III. the number of atoms

Question 31

Four samples: P is 2.0 g of hydrogen, H₂; Q is 4.0 g of helium, He; R is 8.0 g of methane, CH₄; S is 22 g of carbon dioxide, CO₂.
Sample	Substance	Mass / g
P	hydrogen, H₂	2.0
Q	helium, He	4.0
R	methane, CH₄	8.0
S	carbon dioxide, CO₂	22

Which sample in the table contains the greatest number of atoms?

Question 32

What is the volume of 0.500 mol of an ideal gas at 300 K and 150 kPa?

Question 33

A fixed mass of gas starts at a volume of 200 cm³, a temperature of 27 °C and a pressure of 100 kPa. It ends at a temperature of 127 °C and a pressure of 200 kPa, with an unknown volume V.
State	Volume / cm³	Temperature / °C	Pressure / kPa
start	200	27	100
end	V	127	200

The table gives the starting conditions of a fixed mass of gas and the temperature and pressure it is changed to. What is its final volume V?

Question 34

Which statements explain why a real gas deviates from ideal behaviour at high pressure and low temperature? I. The volume of the molecules is no longer negligible compared with the volume of the gas. II. The attractive forces between the molecules become significant. III. The collisions between the molecules become elastic.

Question 35

Measurements on the vapour: mass of vapour 0.210 g; volume of vapour 85.0 cm³; temperature 373 K; pressure 101 kPa.
Quantity	Value
mass of vapour	0.210 g
volume of vapour	85.0 cm³
temperature	373 K
pressure	101 kPa

A sample of a volatile liquid is vaporised completely. The table gives the measurements made on the vapour. What is the relative molecular mass of the liquid?

Question 36

What volume does 3.20 g of oxygen gas, O₂, occupy at STP?

Data-based and structured questions, Paper 1B style

Freezing point from a cooling curvePaper 1B style · SL · 5 marks

A student melts a sample of a pure organic solid in a boiling tube, places a thermometer in the liquid and lets it cool in air. She records the temperature every minute. Each reading has an uncertainty of ±0.5 °C. The table shows her results. The literature value of the melting point of the solid is 45.0 °C.

Cooling of the liquid: time in min and temperature in °C (each ±0.5 °C). 0 min 60.0; 1 min 54.5; 2 min 49.5; 3 min 46.0; 4 min 44.0; 5 min 44.0; 6 min 44.0; 7 min 44.0; 8 min 41.5; 9 min 38.0.
t / min	θ / °C ± 0.5
0	60.0
1	54.5
2	49.5
3	46.0
4	44.0
5	44.0
6	44.0
7	44.0
8	41.5
9	38.0

(a) State the freezing point shown by the data, in K. [1]

(b) Why does the temperature stay constant from 4 min to 7 min? [1]

(d) Calculate the percentage uncertainty in her freezing point of 44.0 °C. [1]

(e) Take a percentage error of 2.2% and a percentage uncertainty of 1.1%. Which conclusion is correct? [1]

Water of crystallisation in a hydrated saltPaper 1B style · SL · 8 marks

A student weighs an empty crucible, adds crystals of hydrated magnesium sulfate, MgSO₄·xH₂O, and weighs it again. She heats the crucible, lets it cool and reweighs it, repeating until the mass is constant. The balance reads to ±0.01 g. The table shows her results.

Results: mass of empty crucible 20.15 g; crucible and hydrated crystals 22.61 g; after first heating 21.42 g; after second heating 21.35 g; after third heating 21.35 g. Each mass ±0.01 g.
Measurement	Mass / g ± 0.01
empty crucible	20.15
crucible + hydrated crystals	22.61
after first heating	21.42
after second heating	21.35
after third heating	21.35

(a) Calculate the mass of water lost, in g. [1]

(b) Calculate the amount of anhydrous magnesium sulfate left in the crucible, in mol. [2]

mol

(d) The mass of water lost comes from two balance readings. Calculate its percentage uncertainty. [2]

(e) Why does the student heat the crucible repeatedly until its mass is constant? [1]

The molar mass of the gas in a lighterPaper 1B style · SL · 6 marks

A student weighs a gas lighter, then releases gas from it under water into an inverted measuring cylinder full of water until 100.0 cm³ of gas has been collected. She dries the lighter and weighs it again. The room temperature is 20 °C and the pressure is 101 kPa. The table shows her results.

Results: mass of lighter before 25.482 g; mass of lighter after 25.256 g; volume of gas collected 100.0 cm³; temperature 20 °C; pressure 101 kPa.
Measurement	Value
mass of lighter before / g	25.482
mass of lighter after / g	25.256
volume of gas / cm³	100.0
temperature / °C	20
pressure / kPa	101

(a) Calculate the amount of gas collected, in mol. [2]

mol

(b) The mass of gas released is 0.226 g. Take an amount of 4.15 × 10⁻³ mol to calculate the molar mass of the gas, in g mol⁻¹. [1]

g mol⁻¹

(c) The gas is butane, C₄H₁₀. Calculate the percentage error in her molar mass of 54.5 g mol⁻¹, taking the true molar mass of butane from its formula. [2]

(d) Which error would make her value of the molar mass too low? [1]

A standard solution of sodium carbonatePaper 2 style · SL · 6 marks

A student dissolves 1.325 g of anhydrous sodium carbonate, Na₂CO₃, in distilled water and makes the solution up to 250.0 cm³ in a volumetric flask.

(a) Calculate the amount of sodium carbonate dissolved, in mol. [2]

mol

(b) Take an amount of 0.0125 mol to calculate the concentration of the solution, in mol dm⁻³. [1]

mol dm⁻³

g dm⁻³

(d) 10.0 cm³ of a 0.0500 mol dm⁻³ solution is diluted with distilled water to 100.0 cm³. Calculate the new concentration, in mol dm⁻³. [1]

mol dm⁻³

(e) Why does the student rinse the beaker used to dissolve the solid into the volumetric flask with distilled water? [1]

The mass spectrum of rubidiumPaper 2 style · HL · 5 marks

The mass spectrum of a sample of rubidium has two peaks. Their abundances relative to the tallest peak are shown in the bar chart.

(a) Calculate the relative atomic mass of rubidium in the sample, to two decimal places. [2]

(b) Calculate the percentage abundance of ⁸⁷Rb. [1]

(d) Why do ⁸⁵Rb and ⁸⁷Rb have the same chemical properties? [1]

Ionising potassium with lightPaper 2 style · HL · 5 marks

The first ionisation energy of potassium is 419 kJ mol⁻¹.

(a) Calculate the energy needed to ionise one gaseous potassium atom, in J. [2]

(b) Take an energy of 6.96 × 10⁻¹⁹ J to calculate the minimum frequency of a photon that can ionise the atom, in Hz. [1]

(d) Between which two successive ionisation energies of potassium is the first large increase? [1]