NSAA 2023 Chemistry S1: Questions & Worked Solutions

Question 41

An experiment is carried out at two different pressures by changing the volume of the reaction vessel.

The experiment measures the rate of the reaction between molecules X and Y to form Z:

X(g) + Y(g) → Z(s)

Assume that the experiments are carried out under exactly the same conditions apart from the difference in pressure.

How will the rate of the reaction change with pressure, if at all, and what is the reason for this?

The options are described in the table below:

| | difference in rate of reaction | reason |
|---|---|---|
| A | the reaction is faster at lower pressure | average kinetic energy of molecules is greater at lower pressure |
| B | the reaction is faster at lower pressure | the rate of collisions is greater between molecules at lower pressure |
| C | the reaction is slower at lower pressure | average kinetic energy of molecules is less at lower pressure |
| D | the reaction is slower at lower pressure | the rate of collisions between molecules is lower at lower pressure |
| E | the reaction rate is the same at both pressures | the average kinetic energy of molecules is the same at both pressures |

A.The reaction is faster at lower pressure, and the reason is that the average kinetic energy of molecules is greater at lower pressure.
B.The reaction is faster at lower pressure, and the reason is that the rate of collisions is greater between molecules at lower pressure.
C.The reaction is slower at lower pressure, and the reason is that the average kinetic energy of molecules is less at lower pressure.
D.The reaction is slower at lower pressure, and the reason is that the rate of collisions between molecules is lower at lower pressure.
E.The reaction rate is the same at both pressures, and the reason is that the average kinetic energy of molecules is the same at both pressures.

Question 42

Which of the following represents the structure of the addition polymer formed from but-1-ene?
A

B

C

D

E

F

A.The repeating unit is $[-CH_2-CH_2-]_n$ .
B.The repeating unit is $[-CH=CH-CH_2-CH_2-]_n$ .
C.The repeating unit is $[-CH(CH_3)-CH(CH_3)-]_n$ .
D.The structure shown is a polymer chain of four repeating units of ethene.
E.The repeating unit is $[-CH_2-CH(C_2H_5)-]_n$ .
F.The repeating unit is $[-CH_2-CH(CH_3)-]_n$ .

Question 43

The chart shows the relative abundances of the isotopes of an element. The chart shows the following data points: (relative mass 64, relative abundance 4), (relative mass 66, relative abundance 3), (relative mass 68, relative abundance 2).

What is the relative atomic mass (

A_r

) of this element?

A.64.0
B.65.4
C.65.8
D.66.0
E.66.6

Question 44

In this question, all solutions have the same concentration in

mol dm^{-3}

.

Three separate experiments were set up using the same volume of each solution:

experiment 1:

LiCl(aq)

and

AgNO_3(aq)

experiment 2:

NaCl(aq)

and

AgNO_3(aq)

experiment 3:

KCl(aq)

and

AgNO_3(aq)

For each experiment, the solid formed was filtered, washed, dried, and weighed.

Which of the following statements is/are correct?

1 Experiment 3 forms the greatest mass of solid.
2 Experiment 3 has a noticeably greater rate of reaction than the others.
3 The reaction taking place in each experiment is a redox reaction.

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

Question 45

How many moles of ions are present in

20 cm^3

of

0.15 mol dm^{-3}

magnesium nitrate solution?

(Ignore ions produced by dissociation of water.)

A.0.003 mol
B.0.006 mol
C.0.009 mol
D.0.018 mol
E.0.133 mol
F.0.400 mol

Question 46

Silicon is directly below carbon in the Periodic Table and has a melting point of 1414 °C.

Which of the following statements explains why silicon has a high melting point?

A.It forms ions with a charge of 4+.
B.Its structure is a giant ionic lattice.
C.It has a strong attraction between positive nuclei and delocalised electrons.
D.It has strong intermolecular forces.
E.Covalent bonds are broken on melting.

Question 47

Atoms of element Q have two full shells of electrons and the third shell requires one more electron to gain a noble gas configuration.

Which row of the table correctly describes the elements near to Q in the Periodic Table?

A.Above Q: requires one more electron to fill a second shell of electrons. Below Q: gains an electron less favourably than Q. Left of Q: the atom contains one fewer proton than Q. Right of Q: is very unreactive compared to Q.
B.Above Q: gains an electron more favourably than Q. Below Q: the atom contains more protons than Q. Left of Q: is found in Period 3. Right of Q: is a halogen.
C.Above Q: requires one more electron to fill a second shell of electrons. Below Q: gains an electron less favourably than Q. Left of Q: is an alkaline earth metal. Right of Q: the atom contains one more proton than Q.
D.Above Q: is found in Period 3. Below Q: contains an extra full shell of electrons compared to Q. Left of Q: the atom contains one fewer proton than Q. Right of Q: is very unreactive compared to Q.
E.Above Q: gains an electron more favourably than Q. Below Q: the atom contains more protons than Q. Left of Q: the atom has an atomic number greater than Q. Right of Q: is found in Period 3.

Question 48

A simple ion of an element has a mass number

x

, an atomic number

\frac{x-1}{2}

and a charge of -1.

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

A.protons: $\frac{x-1}{2}$ , neutrons: $\frac{x-1}{2}$ , electrons: $\frac{x-1}{2}$
B.protons: $\frac{x-1}{2}$ , neutrons: $\frac{x+1}{2}$ , electrons: $\frac{x+1}{2}$
C.protons: $\frac{x-1}{2}$ , neutrons: $\frac{x+1}{2}$ , electrons: $\frac{x-1}{2}$
D.protons: $\frac{x-1}{2}$ , neutrons: $\frac{x-1}{2}$ , electrons: $\frac{x+1}{2}$
E.protons: $\frac{x+1}{2}$ , neutrons: $\frac{x-1}{2}$ , electrons: $\frac{x+1}{2}$
F.protons: $\frac{x+1}{2}$ , neutrons: $\frac{x-1}{2}$ , electrons: $\frac{x-1}{2}$

Question 49

Titanium metal can be extracted from titanium(IV) chloride,

TiCl_4

.

Titanium(IV) chloride is heated to 1000 °C with either sodium or magnesium metal in an atmosphere of argon.

Which one of the following statements is correct?

(

A_r

values: Na = 23; Mg = 24; Cl = 35.5; Ti = 48)

A.A greater mass of magnesium chloride than sodium chloride is produced for each tonne of titanium made.
B.The atmosphere of argon is used as a catalyst.
C.In each reaction equation, the ratio of the reacting metal to titanium(IV) chloride is the same.
D.Titanium is a weaker oxidising agent than either sodium or magnesium.
E.A smaller mass of magnesium than sodium is required to produce 500 kg of titanium.

Question 50

Ethene gas and hydrogen gas react to form ethane gas.

The energy change for this reaction is -150 kJ

mol^{-1}

.

Using the provided data, what is the mean C-H bond energy?

(Bond energy data: H-H = 430 kJ

mol^{-1}

; C-C = 350 kJ

mol^{-1}

; C=C = 600 kJ

mol^{-1}

)

A.115 kJ $mol^{-1}$
B.200 kJ $mol^{-1}$
C.230 kJ $mol^{-1}$
D.265 kJ $mol^{-1}$
E.400 kJ $mol^{-1}$
F.415 kJ $mol^{-1}$
G.465 kJ $mol^{-1}$
H.830 kJ $mol^{-1}$

Question 51

A water treatment unit processes

355000 dm^3

of drinking water each day.

0.4 mg of chlorine gas is used to kill the bacteria in

1 dm^3

of the source water.

What volume of chlorine gas, if measured at room temperature and pressure, is used each day at the water treatment unit?

(

A_r

value: Cl = 35.5. Assume that one mole of a gas occupies

24 dm^3

at room temperature and pressure.)

A. $6 dm^3$
B. $12 dm^3$
C. $48 dm^3$
D. $96 dm^3$
E. $300 dm^3$
F. $600 dm^3$

Question 52

Element X is in Group 13, Period 4. It consists of atoms of two isotopes with mass numbers 69 and 71. The relative atomic mass of element X is 69.7.

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

1 75% of the atoms of element X have mass number 69.
2 An atom of element X has three electrons in its outer shell.
3 Element X forms an oxide with formula

X_2O_3

that reacts with acids.

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

Question 53

One mole of copper reacts completely with an excess of concentrated nitric acid.

A gaseous oxide of nitrogen is one of the products of the reaction. The volume of this gas is

48 dm^3

when measured at room temperature and pressure.

The oxidation state of the nitrogen in the gaseous oxide is one less than the oxidation state of the nitrogen in the nitric acid.

Which of the following could be the equation for this reaction?

(Assume that one mole of any gas occupies

24 dm^3

at room temperature and pressure.)

A. $Cu + 2HNO_3 \rightarrow CuNO_3 + NO_2 + H_2O$
B. $Cu + 2HNO_3 \rightarrow CuO + 2NO + O_2 + H_2O$
C. $Cu + 2HNO_3 \rightarrow CuO + 2N_2O_4 + H_2O$
D. $Cu + 4HNO_3 \rightarrow Cu(NO_3)_2 + N_2O_4 + 2H_2O$
E. $Cu + 4HNO_3 \rightarrow Cu(NO_3)_2 + 2NO_2 + 2H_2O$
F. $3Cu + 8HNO_3 \rightarrow 3Cu(NO_3)_2 + 2NO + 4H_2O$
G. $3Cu + 8HNO_3 \rightarrow Cu(NO_3)_2 + 2CuO + 6N_2O_4 + 4H_2O$

Question 54

Two experiments were carried out using separate samples of a solution of an acid of concentration

0.40 mol dm^{-3}

(

36 g dm^{-3}

) and the following observations were made.

•

25 cm^3

of the acid solution exactly neutralised

100 cm^3

of

0.20 mol dm^{-3}

sodium hydroxide solution.

• Bubbles of gas were given off when magnesium ribbon was added to the acid solution.

Which of the following statements can be deduced from this information?

1 It is a monoprotic acid.
2 It is a strong acid.
3 The acid has a relative molar mass (

M_r

) of 90.

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

Question 55

When methanol is burned in the apparatus shown it gives out

720 kJ mol^{-1}

. However, only 80% of the energy released is transferred into the water.

The starting temperature of the water is 12°C.

What mass of methanol would need to be burned to give a 60°C temperature rise in the water?

(

M_r

value: methanol = 32. Assume that the specific heat capacity of water =

4 J g^{-1} °C^{-1}

)

A.1.28 g
B.1.60 g
C.1.92 g
D.2.00 g
E.2.40 g

Question 56

A student electroplates a solid metal ball with copper.

The student dissolves 80.0 g of anhydrous copper(II) sulfate in water and makes up the solution to exactly

500 cm^3

to use as the electrolyte.

Two electrodes are placed in this solution. One electrode is the ball to be electroplated and the other electrode is an inert graphite electrode. The electrodes are connected to a battery.

After some time, the ball is removed and is found to be coated with 8.00 g of copper. Water is added to the remaining solution to give a final volume of exactly

500 cm^3

.

What is the final concentration of the copper(II) ions in solution?

(

A_r

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

A. $0.25 mol dm^{-3}$
B. $0.38 mol dm^{-3}$
C. $0.45 mol dm^{-3}$
D. $0.50 mol dm^{-3}$
E. $0.75 mol dm^{-3}$
F. $0.90 mol dm^{-3}$
G. $1.0 mol dm^{-3}$

Question 57

The structure of cyclohexa-1,4-diene is:

Bromine is dissolved in inert organic solvent to form

0.250 mol dm^{-3}

of bromine solution.

What is the minimum volume of this bromine solution required to react completely with

0.10 cm^3

of cyclohexa-1,4-diene?

(

M_r

value: cyclohexa-1,4-diene = 80. Density of cyclohexa-1,4-diene =

0.84 g cm^{-3}

)

A. $0.042 cm^3$
B. $0.084 cm^3$
C. $0.0042 cm^3$
D. $0.0084 cm^3$
E. $0.042 dm^3$
F. $0.084 dm^3$
G. $0.0042 dm^3$
H. $0.0084 dm^3$

Question 58

The relative tendency for metals to form positive ions in solution can be measured using the following apparatus:

Electrons can pass from metal 1 to metal 2 via the external circuit. The difference in the tendency of the metals to form positive ions is given by the reading on the voltmeter. The higher the reading on the voltmeter the greater the difference in the tendency of the pair of metals to form positive ions.

Results from three experiments are given in the following table.

| experiment | metal 1 | metal 2 | reading on voltmeter / V |
|---|---|---|---|
| 1 | P | Q | +0.62 |
| 2 | S | Q | +0.30 |
| 3 | S | R | +1.24 |

Using the information in the table, what is the order of reactivity of the four metals P, Q, R and S, from most reactive to least reactive?

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

Question 59

A sample of aluminium ore (bauxite) contains 75.0% by mass of hydrated aluminium oxide.

Hydrated aluminium oxide is one mole of aluminium oxide combined with two moles of water.

What is the minimum mass of this sample of bauxite that is required to produce 108 tonnes of aluminium?

(1 tonne =

1 \times 10^6 g

.

A_r

values: H = 1; O = 16; Al = 27)

A.184 tonnes
B.207 tonnes
C.272 tonnes
D.276 tonnes
E.368 tonnes
F.421 tonnes
G.592 tonnes
H.736 tonnes

Question 60

Equal amounts of carbon dioxide and carbon monoxide are produced when 2.0 mol of propanol,

C_3H_7OH

, are reacted with a limited supply of oxygen. Water is the only other product in this reaction.

How many moles of oxygen molecules are used in this reaction?

A.3.5 mol
B.7.0 mol
C.7.5 mol
D.8.5 mol
E.15 mol
F.17 mol