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NSAA 2019 Chemistry S1

16 questions16 marksUpdated June 2026

The NSAA 2019 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 39

Four samples, labelled W, X, Y and Z, were investigated using paper chromatography with a solvent that caused any mixtures present to be fully separated. The results are shown in the chromatogram.

Exam diagram

What is the

R_f

value of the spot with the strongest attraction to the mobile phase relative to the stationary phase and that is from a sample containing only one substance?

A.0.50
B.0.60
C.0.67
D.0.75
E.0.80
F.0.90

Answer: E

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Question 40

A mass spectrometer is a device that can measure the mass of isotopes. It shows this data as a spectrum, giving both the relative mass and the percentage abundance of each isotope.

The charts indicate the relative mass and percentage abundance for lithium atoms, carbon atoms and oxygen atoms found in a sample taken from a nuclear reactor.

Exam diagram

Exam diagram

Exam diagram

Using this data, what is the largest possible relative molar mass of lithium carbonate?

A.35
B.38
C.45
D.67
E.74
F.75
G.81

Answer: G

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Question 41

The following information about metals labelled P, Q, R and S is given.

* Metals P and S can be extracted by electrolysis, but not by reaction with carbon.
* Metals Q and R can be extracted by reaction with carbon.
* Metal S forms positive ions more readily than metal P.
* Metal R reacts with the oxide of metal Q.

What is the order of reactivity of these four metals, starting with the most reactive?

A.P, S, Q, R
B.P, S, R, Q
C.Q, R, P, S
D.Q, R, S, P
E.R, Q, P, S
F.R, Q, S, P
G.S, P, Q, R
H.S, P, R, Q

Answer: H

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Question 42

A simple ion of an element with atomic number

x

has a mass number of

(2x + 2)

.

The ion has a charge of -2.

How many protons, neutrons and electrons are present in this ion?

| | protons | neutrons | electrons |
|---|---|---|---|
| A |

x-2

|

x+4

|

x-2

|
| B |

x-2

|

x+4

|

x

|
| C |

x-2

|

x+4

|

x+2

|
| D |

x

|

x+2

|

x-2

|
| E |

x

|

x+2

|

x

|
| F |

x

|

x+2

|

x+2

|

A. $x-2$ protons, $x+4$ neutrons, $x-2$ electrons
B. $x-2$ protons, $x+4$ neutrons, $x$ electrons
C. $x-2$ protons, $x+4$ neutrons, $x+2$ electrons
D. $x$ protons, $x+2$ neutrons, $x-2$ electrons
E. $x$ protons, $x+2$ neutrons, $x$ electrons
F. $x$ protons, $x+2$ neutrons, $x+2$ electrons

Answer: F

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Question 43

A 116 g sample of an oxide of iron contains 84 g of iron.

Which of the following is the empirical formula of this oxide of iron?

(

A_r

values: O = 16; Fe = 56)

A.FeO
B. $Fe_2O_2$
C. $Fe_3O_2$
D. $Fe_2O_3$
E. $Fe_3O_4$

Answer: E

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Question 44

Which of the following chemical equations represent(s) a redox reaction?

1.

2Cu^{2+} + 4I^- \rightarrow 2CuI + I_2

2.

Al^{3+} + 3e^- \rightarrow Al

3.

2Ag^+ + 2OH^- \rightarrow Ag_2O + H_2O

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: B

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Question 45

X is an anhydrous salt of iron containing one type of cation and one type of anion.

An aqueous solution of X gives a white precipitate when aqueous barium chloride is added in the presence of hydrochloric acid.

On adding aqueous sodium hydroxide to an aqueous solution of X, a brown precipitate formed immediately.

The relative atomic mass of iron is 56, and its atomic number is 26.

What is the relative molar mass of X?

(

A_r

values: C = 12; N = 14; O = 16; S = 32; Cl = 35.5; Br = 80)

A.127
B.152
C.162.5
D.208
E.264
F.272
G.360
H.400

Answer: H

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Question 46

In the electrolysis of dilute sulfuric acid, hydrogen gas is formed at the negative electrode (cathode) and oxygen gas is formed at the positive electrode (anode).

If 100 g of hydrogen gas is formed in the electrolysis of dilute sulfuric acid, what mass of oxygen gas is also formed?

(

A_r

values: H = 1; O = 16)

A.50 g
B.100 g
C.200 g
D.800 g
E.1600 g

Answer: D

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Question 47

0.005 mol of a chloride of element X was dissolved in water and then reacted with excess silver nitrate solution to form a precipitate of silver chloride, AgCl. This precipitate is the only product of this reaction that contains chlorine.

After filtering, washing and drying, the mass of the precipitate was recorded to be 1.435 g.

Which of the following could be the formula of the chloride of X?

(

M_r

value: AgCl = 143.5)

A. $X_5Cl$
B. $X_2Cl$
C.XCl
D. $XCl_2$
E. $XCl_5$

Answer: D

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Question 48

A chemical equation that represents the reaction of phosphorus with concentrated nitric acid is:

P_4 + wHNO_3 + H_2O \rightarrow xH_3PO_4 + yNO + zNO_2

What is the value of the sum

w + x + y + z

?

A.24
B.28
C.30
D.32
E.36

Answer: A

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Question 49

A 2.40 g lump of magnesium was added to 500 cm³ of a 2.00 mol dm⁻³ solution of HCl in a conical flask that was on an electronic balance. The neck of the flask was plugged with cotton wool, and the decrease in mass of the flask and its contents was recorded at regular intervals.

The mass of the hydrogen released (equal to the mass loss recorded) was plotted against time. The result is line 1 on the graph.

Exam diagram

Which of the following experiments performed under the same conditions would give line 2?

(

A_r

value: Mg = 24.0)

A.a 2.40 g lump of magnesium added to 500 cm³ of 2.00 mol dm⁻³ $H_2SO_4$
B.2.40 g of magnesium powder added to 500 cm³ of 2.00 mol dm⁻³ HCl
C.a 2.40 g lump of magnesium added to 1000 cm³ of 2.00 mol dm⁻³ HCl
D.a 4.80 g lump of magnesium added to 500 cm³ of 2.00 mol dm⁻³ HCl
E.4.80 g of magnesium powder added to 500 cm³ of 2.00 mol dm⁻³ HCl

Answer: D

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Question 50

A technician needs to separate three liquids (X, Y and Z) which have been accidentally mixed together. None of the liquids react with each other.

| liquid | X | Y | Z |
|---|---|---|---|
| boiling point / °C | 65 | 51 | 100 |
| density / g cm⁻³ | 0.79 | 0.68 | 1.00 |

X and Z are miscible, but Y is immiscible with both X and Z.

The technician uses a separating funnel to separate the upper and lower layers of the mixture.

What should the technician do next to maximise separation of the three liquids?

A.distil the lower layer at 51 °C
B.distil the lower layer at 65 °C
C.distil the lower layer at 100 °C
D.distil the upper layer at 51 °C
E.distil the upper layer at 65 °C
F.distil the upper layer at 100 °C

Answer: B

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Question 51

In each of the following procedures an excess of the metal is added to 1.0 dm³ of a 1.0 mol dm⁻³ solution of the acid.

* copper added to sulfuric acid
* iron added to hydrochloric acid
* magnesium added to sulfuric acid
* zinc added to hydrochloric acid

Which row in the following table identifies combinations of metal and acid that will react and produce the largest, and the smallest, theoretical mass of anhydrous salt?

(

M_r

values:

CuSO_4

= 160;

FeCl_2

= 127;

MgSO_4

= 120;

ZnCl_2

= 136)

| | reaction that produces the largest mass of salt | reaction that produces the smallest mass of salt |
|---|---|---|
| A | Cu and

H_2SO_4

| Fe and HCl |
| B | Cu and

H_2SO_4

| Mg and

H_2SO_4

|
| C | Fe and HCl | Zn and HCl |
| D | Mg and

H_2SO_4

| Fe and HCl |
| E | Mg and

H_2SO_4

| Zn and HCl |
| F | Zn and HCl | Mg and

H_2SO_4

|

A.Largest: Cu and $H_2SO_4$ , Smallest: Fe and HCl
B.Largest: Cu and $H_2SO_4$ , Smallest: Mg and $H_2SO_4$
C.Largest: Fe and HCl, Smallest: Zn and HCl
D.Largest: Mg and $H_2SO_4$ , Smallest: Fe and HCl
E.Largest: Mg and $H_2SO_4$ , Smallest: Zn and HCl
F.Largest: Zn and HCl, Smallest: Mg and $H_2SO_4$

Answer: D

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Question 52

3.4 g of an impure sample of silicon tetrachloride is reacted with water. The mixture is then filtered and the resulting solution made up to 250 cm³.

SiCl_4(l) + 2H_2O(l) \rightarrow SiO_2(s) + 4HCl(aq)

12.5 cm³ of this solution is neutralised exactly by 20.0 cm³ of 0.100 mol dm⁻³ sodium hydroxide.

What is the percentage purity of the silicon tetrachloride?

(

M_r

value:

SiCl_4

= 170. Assume that the impurity does not react.)

A.1.7%
B.2.5%
C.10%
D.32%
E.50%

Answer: E

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Question 53

The Haber process is represented by the following chemical equation:

N_2 + 3H_2 \rightarrow 2NH_3

What is the overall enthalpy change for the reaction?

(Bond enthalpies:

N\equiv N

= 945 kJ mol⁻¹; H-H = 435 kJ mol⁻¹; N-H = 390 kJ mol⁻¹)

A.+90 kJ mol⁻¹
B.-90 kJ mol⁻¹
C.+990 kJ mol⁻¹
D.-990 kJ mol⁻¹
E.+1080 kJ mol⁻¹
F.-1080 kJ mol⁻¹

Answer: B

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Question 54

The diagram shows the electrolysis of molten lead(II) bromide,

PbBr_2

, using graphite electrodes to separate the compound into its elements.

Exam diagram

Which of the following statements about this electrolysis is/are correct?

1. Lead is formed at the negative electrode.
2. Electrons flow through the external circuit away from the positive electrode towards the negative electrode.
3. Bromine molecules and lead are produced in a 2:1 molar ratio.

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: E

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