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NSAA 2018 Chemistry S1

16 questions16 marksUpdated June 2026

The NSAA 2018 Chemistry S1 paper in full: all 16 questions, each with its answer. NSAA is the Natural Sciences Admissions Assessment. Sit it cold under exam timing, mark it, then work back through anything you missed using the solutions below.

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Question 37

Which row in the following table gives the numbers of protons, neutrons and electrons in

{}^{64}_{29}Cu^{2+}

?

| | number of protons | number of neutrons | number of electrons |
|---|---|---|---|
| A | 27 | 33 | 27 |
| B | 27 | 35 | 29 |
| C | 29 | 35 | 27 |
| D | 29 | 35 | 29 |
| E | 31 | 33 | 29 |
| F | 31 | 35 | 29 |

A.27 protons, 33 neutrons, 27 electrons
B.27 protons, 35 neutrons, 29 electrons
C.29 protons, 35 neutrons, 27 electrons
D.29 protons, 35 neutrons, 29 electrons
E.31 protons, 33 neutrons, 29 electrons
F.31 protons, 35 neutrons, 29 electrons

Answer: C

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Question 38

The following exothermic reaction reaches equilibrium at room temperature.

C_2H_5OH(l) + CH_3COOH(l) \rightleftharpoons CH_3COOC_2H_5(l) + H_2O(l)

Which of the following changes, when applied independently, will alter the position of the equilibrium?

1 increasing the temperature by 25 °C
2 adding 20 cm³ of water to the equilibrium mixture
3 adding a catalyst
4 adding an extra 0.5 mol of ethanol (

C_2H_5OH

)

A.1 only
B.1 and 3 only
C.1, 2 and 4 only
D.2 and 4 only
E.1, 2, 3 and 4

Answer: C

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Question 39

What is the overall process that takes place at the cathode (negative electrode) in the electrolysis of dilute aqueous sodium sulfate?

A.
$2H^+ + 2e^- \rightarrow H_2$
B.
$2O^{2-} \rightarrow O_2 + 4e^−$
C.
$4OH^- \rightarrow O_2 + 2H_2O + 4e^−$
D.
$Na^+ + e^− \rightarrow Na$
E.
$SO_4^{2-} \rightarrow SO_2 + O_2 + 2e^−$

Answer: A

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Question 40

A mass spectrum of a sample of element X with atomic number 5 is shown. The graph shows percentage abundance on the y-axis against mass/charge on the x-axis. There are two peaks: one at mass/charge 10 with an abundance of approximately 25%, and one at mass/charge 11 with an abundance of 100%.

Using the data, which row in the following table best describes the position of X in the Periodic Table and the relative atomic mass of this sample of X?

| | Period | Group | relative atomic mass |
|---|---|---|---|
| A | 1 | 15 | 10.2 |
| B | 1 | 15 | 10.8 |
| C | 2 | 13 | 10.2 |
| D | 2 | 13 | 10.8 |
| E | 3 | 2 | 10.2 |
| F | 3 | 2 | 10.8 |

Exam diagram

A.Period 1, Group 15, relative atomic mass 10.2
B.Period 1, Group 15, relative atomic mass 10.8
C.Period 2, Group 13, relative atomic mass 10.2
D.Period 2, Group 13, relative atomic mass 10.8
E.Period 3, Group 2, relative atomic mass 10.2
F.Period 3, Group 2, relative atomic mass 10.8

Answer: D

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Question 41

The gases nitrogen, oxygen and argon can be separated from liquefied air by fractional distillation.

Given the data in the table, in which order would the gases be collected?

| | melting point / °C | boiling point / °C |
|---|---|---|
| nitrogen | -210 | -196 |
| oxygen | -218 | -183 |
| argon | -189 | -186 |

A.nitrogen, oxygen, argon
B.nitrogen, argon, oxygen
C.oxygen, nitrogen, argon
D.oxygen, argon, nitrogen
E.argon, nitrogen, oxygen
F.argon, oxygen, nitrogen

Answer: B

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Question 42

Concentrated aqueous sodium chloride was electrolysed. After a few minutes, the remaining electrolyte solution was tested with a pH probe at 25 °C.

The gases produced at the electrodes were collected and tested with a colourless aqueous solution of sodium bromide.

Which row in the following table best describes the observations in these tests?

| | pH of the remaining solution | test of gas from anode (positive electrode) | test of gas from cathode (negative electrode) |
|---|---|---|---|
| A | 2 | no observable change | no observable change |
| B | 2 | no observable change | orange solution forms |
| C | 7 | orange solution forms | no observable change |
| D | 7 | orange solution forms | orange solution forms |
| E | 12 | orange solution forms | no observable change |
| F | 12 | no observable change | orange solution forms |

A.pH 2, test of gas from anode: no observable change, test of gas from cathode: no observable change
B.pH 2, test of gas from anode: no observable change, test of gas from cathode: orange solution forms
C.pH 7, test of gas from anode: orange solution forms, test of gas from cathode: no observable change
D.pH 7, test of gas from anode: orange solution forms, test of gas from cathode: orange solution forms
E.pH 12, test of gas from anode: orange solution forms, test of gas from cathode: no observable change
F.pH 12, test of gas from anode: no observable change, test of gas from cathode: orange solution forms

Answer: E

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Question 43

The following equations show the main reactions that take place in a blast furnace during the extraction of iron and the removal of the impurities:

C + O_2 \rightarrow CO_2

CO_2 + C \rightarrow 2CO

Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2

CaCO_3 \rightarrow CaO + CO_2

CaO + SiO_2 \rightarrow CaSiO_3

Which row in the following table correctly identifies whether the underlined substance is oxidised, or reduced, or neither? The underlined substances are

CO_2

in the second equation,

CaCO_3

in the fourth equation, and

CaO

in the fifth equation.

| |

CO_2

|

CaCO_3

|

CaO

|
|---|---|---|---|
| A | oxidised | reduced | neither |
| B | oxidised | neither | neither |
| C | oxidised | reduced | oxidised |
| D | oxidised | neither | oxidised |
| E | reduced | reduced | neither |
| F | reduced | neither | neither |
| G | reduced | reduced | oxidised |
| H | reduced | neither | oxidised |

A. $CO_2$ : oxidised, $CaCO_3$ : reduced, $CaO$ : neither
B. $CO_2$ : oxidised, $CaCO_3$ : neither, $CaO$ : neither
C. $CO_2$ : oxidised, $CaCO_3$ : reduced, $CaO$ : oxidised
D. $CO_2$ : oxidised, $CaCO_3$ : neither, $CaO$ : oxidised
E. $CO_2$ : reduced, $CaCO_3$ : reduced, $CaO$ : neither
F. $CO_2$ : reduced, $CaCO_3$ : neither, $CaO$ : neither
G. $CO_2$ : reduced, $CaCO_3$ : reduced, $CaO$ : oxidised
H. $CO_2$ : reduced, $CaCO_3$ : neither, $CaO$ : oxidised

Answer: F

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Question 44

X, Y and Z have the same electron configuration.

X is an atom, Y is a monatomic anion and Z is a monatomic cation.

Which of the following statements is always correct?

A.Anion Y has fewer protons than atom X.
B.Cation Z has more electrons than protons.
C.X, Y and Z are in the same group of the Periodic Table.
D.X, Y and Z have consecutive atomic numbers.
E.X, Y and Z have the same mass number.

Answer: A

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Question 45

In the Contact process, sulfur dioxide reacts with oxygen to make sulfur trioxide in a reversible reaction.

SO_2(g) + \frac{1}{2}O_2(g) \rightleftharpoons SO_3(g)

When 5.00 mol of

SO_2

and 11.0 mol of

O_2

are allowed to reach equilibrium at 450 °C, 80.0% of the

SO_2

is converted to

SO_3

.

What is the volume of the resulting mixture?

(Assume that temperature and pressure are constant, and that at this temperature the volume of one mole of gas is 60.0 dm³.)

A.240 dm³
B.336 dm³
C.600 dm³
D.720 dm³
E.840 dm³
F.960 dm³

Answer: E

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Question 46

The non-metallic element phosphorus forms two stable chlorides:

PCl_3

(boiling point 76 °C) and

PCl_5

(boiling point 161 °C).

Which of the following statements explain(s) the difference in boiling points?

1 There are more covalent bonds in

PCl_5

so more energy is required to break them.
2 The forces between the molecules in liquid

PCl_5

are stronger.
3 The covalent bonds in

PCl_3

are weaker so less energy is required to break them.

A.none of them
B.1 only
C.2 only
D.3 only
E.1 and 2 only
F.1 and 3 only
G.2 and 3 only
H.1, 2 and 3

Answer: C

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Question 47

A student calculated the mass of anhydrous copper(II) sulfate (

CuSO_4

) required to make 250 cm³ of an aqueous solution of concentration 0.200 mol dm⁻³.

However, the student mistakenly made the solution using the same mass of hydrated copper(II) sulfate (

CuSO_4·5H_2O

) instead.

What is the concentration, in mol dm⁻³, of the solution made with the hydrated copper(II) sulfate?

(

A_r

values: Cu = 64; S = 32; O = 16; H = 1.0)

A.0.128 mol dm⁻³
B.0.160 mol dm⁻³
C.0.180 mol dm⁻³
D.0.200 mol dm⁻³
E.0.223 mol dm⁻³
F.0.313 mol dm⁻³

Answer: A

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Question 48

Bromine is an element in Group 17 of the Periodic Table.

Which of the following statements is/are correct about the element bromine?

1 Bromine will oxidise chloride ions in aqueous solution to form chlorine.
2 Bromine has a lower boiling point than chlorine.
3 Bromine reacts with calcium (Group 2) to form a compound containing 80% bromine by mass.

(

A_r

values: Cl = 35.5; Ca = 40; Br = 80)

A.none of them
B.1 only
C.2 only
D.3 only
E.1 and 2 only
F.1 and 3 only
G.2 and 3 only
H.1, 2 and 3

Answer: D

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Question 49

Paper chromatography was used to separate three mixtures of amino acids. The mixtures were labelled P, Q and R. The chromatogram is shown below.

Each mixture contains some of the five amino acids in the following table. The

R_f

values were measured for each amino acid with the solvent used to produce the chromatogram.

| amino acid |

R_f

value |
|---|---|
| asparagine | 0.50 |
| glutamic acid | 0.30 |
| glycine | 0.26 |
| leucine | 0.71 |
| valine | 0.61 |

Which of the following statements is/are correct?

1 Mixture P contains valine and glycine.
2 Leucine is found in all three mixtures.
3 Glutamic acid is the least mobile amino acid with this solvent.
4 Mixtures P and Q both contain asparagine.

Exam diagram

A.1 and 2 only
B.1 and 4 only
C.2 and 3 only
D.3 only
E.4 only

Answer: B

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Question 50

Dilute hydrochloric acid and magnesium were mixed and the total volume of gas released was measured over time. A graph of volume of gas (cm³) versus time (s) is shown. At time = 2 seconds, the volume of gas released is 24 cm³.

What is the average rate of reaction, in g s⁻¹, with respect to the magnesium over the first two seconds?

(

A_r

value: Mg = 24. Assume that the volume of one mole of gas is 24 dm³.)

Exam diagram

A.0.012 g s⁻¹
B.0.024 g s⁻¹
C.0.048 g s⁻¹
D.12 g s⁻¹
E.24 g s⁻¹
F.48 g s⁻¹

Answer: A

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Question 51

Copper can react with concentrated nitric acid to form the gas nitrogen monoxide.

3Cu + aHNO_3 \rightarrow b Cu(NO_3)_2 + c H_2O + d NO

What is the value of a when the equation is balanced?

A.6
B.7
C.8
D.9
E.10
F.11
G.12

Answer: C

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Question 52

A small amount of a solid mixture, containing calcium carbonate and an inert substance, was added to 50.00 cm³ dilute hydrochloric acid of concentration 0.1000 mol dm⁻³.

CaCO_3 + 2HCl \rightarrow CaCl_2 + CO_2 + H_2O

After all of the calcium carbonate had reacted, the solution was heated to drive off the carbon dioxide.

The resulting solution was neutralised by 12.50 cm³ of 0.1000 mol dm⁻³ sodium hydroxide solution.

What was the mass of calcium carbonate in the mixture added to the hydrochloric acid?

(

M_r

value:

CaCO_3

= 100.0)

A.0.06250 g
B.0.1250 g
C.0.1875 g
D.0.3750 g
E.0.6250 g
F.0.7500 g

Answer: C

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