Question 1

1 mark

The atomic numbers of three elements

X, Y,

and

Z

are

n-1, n,

and

n+10

respectively. Element

Y

is the noble gas in Period 2. Which of the following statements is correct?

A.Element $X$ reacts with element $Z$ to form an ionic compound with formula $ZX_2$ .
B.Element $Z$ is in the same period as element $Y$ .
C.The element with atomic number $n+8$ is in Period 4.
D.The oxide of element $Z$ reacts with water to form an acidic solution.
E.The element with atomic number $n+1$ is more electronegative than element $X$ .

Answer: A

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Question 2

1 mark

Element

X

is in Period 4, Group 2 of the Periodic Table. Element

Y

is in Period 3, Group 16 of the Periodic Table. (Groups are numbered 1–18 as per IUPAC conventions).

Which of the following statements is/are correct?

1. Element

X

is an alkaline earth metal.
2. Element

Y

has a smaller atomic radius than the element in Period 3, Group 14.
3. The compound formed between

X

and

Y

is ionic and has the formula

X_2Y

.

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

Answer: B

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Question 3

1 mark

Consider the following three elements from the Periodic Table:

- Element

X

: is in Period 4 and Group 2.
- Element

Y

: its neutral atom has exactly 7 electrons in its third shell and no electrons in its fourth shell.
- Element

Z

: is the halogen in the same period as element

X

.

Which of the following statements is/are correct?

1. The neutral atom of

Z

has 15 more protons than the neutral atom of

X

.
2. Element

Y

is more reactive than the halogen in Period 2.
3. The ion

X^{2+}

and the ion

Y^{-}

have the same electron configuration.

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

Answer: D

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Question 4

1 mark

Four elements are identified by their positions in the Periodic Table:
- Element

X

: Group 2, Period 3
- Element

Y

: Group 2, Period 4
- Element

Z

: Group 17, Period 2
- Element

W

: Group 17, Period 3

Which of the following correctly compares the reactivity of these elements and provides a valid justification for the trend observed in Group 17?

A. $Y$ is more reactive than $X$ , and $Z$ is more reactive than $W$ ; Group 17 reactivity decreases down the group because increased shielding and atomic radius weaken the attraction between the nucleus and an incoming electron.
B. $X$ is more reactive than $Y$ , and $W$ is more reactive than $Z$ ; Group 17 reactivity increases down the group because the atomic radius increases, allowing for more electrons to be held in the outer shell.
C. $Y$ is more reactive than $X$ , and $W$ is more reactive than $Z$ ; Group 17 reactivity increases down the group because the increasing nuclear charge more effectively attracts incoming electrons.
D. $X$ is more reactive than $Y$ , and $Z$ is more reactive than $W$ ; Group 17 reactivity decreases down the group because the first ionisation energy increases, making it harder to form ions.
E. $Y$ is more reactive than $X$ , and $Z$ is more reactive than $W$ ; Group 17 reactivity decreases down the group because the atomic mass increases, which reduces the mobility of the atoms during a reaction.

Answer: A

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Question 5

1 mark

A

0.14\,\text{g}

sample of pure

^{14}\text{C}

is completely reacted with an excess of

^{16}\text{O}_2

gas to produce

^{14}\text{C}^{16}\text{O}_2

. Given that the atomic numbers (

Z

) of carbon and oxygen are

6

and

8

respectively, and the Avogadro constant

N_A = 6.0 \times 10^{23}\,\text{mol}^{-1}

, what is the total number of protons in the nuclei of the product molecules?

A. $3.6 \times 10^{22}$
B. $8.4 \times 10^{22}$
C. $1.32 \times 10^{23}$
D. $1.44 \times 10^{23}$
E. $1.32 \times 10^{24}$

Answer: C

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Question 6

1 mark

A binary ionic compound is formed between a metal

M

from Group 2 of the Periodic Table and a non-metal

X

from Group 15. A pure sample of this compound is found to contain

0.12\,\text{mol}

of

M

and

2.48\,\text{g}

of

X

.

Using this information, what is the relative atomic mass (

A_r

) of

X

?

A.10.3
B.13.8
C.20.7
D.31.0
E.62.0

Answer: D

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Question 7

1 mark

When solid sodium hydrogen carbonate is added to an excess of dilute hydrochloric acid at

25^\circ\text{C}

and

100\,\text{kPa}

, the solid reacts and disappears to form a clear, colorless solution while a gas is evolved. Which of the following balanced chemical equations correctly represents this reaction, including all state symbols?

A. $\text{NaHCO}_3(\text{s}) + \text{HCl}(\text{aq}) \rightarrow \text{NaCl}(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})$
B. $\text{NaHCO}_3(\text{aq}) + \text{HCl}(\text{aq}) \rightarrow \text{NaCl}(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})$
C. $\text{NaHCO}_3(\text{s}) + \text{HCl}(\text{aq}) \rightarrow \text{NaCl}(\text{s}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})$
D. $\text{NaHCO}_3(\text{s}) + \text{HCl}(\text{aq}) \rightarrow \text{NaCl}(\text{aq}) + \text{H}_2\text{O}(\text{aq}) + \text{CO}_2(\text{g})$
E. $\text{NaHCO}_3(\text{s}) + \text{HCl}(\text{l}) \rightarrow \text{NaCl}(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})$

Answer: A

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Question 8

1 mark

Consider the following two reversible gas-phase reactions, both initially at equilibrium in separate closed containers:

Reaction 1:

\text{N}_2(\text{g}) + 3\text{H}_2(\text{g}) \rightleftharpoons 2\text{NH}_3(\text{g}) \quad \Delta H = -92\,\text{kJ}\,\text{mol}^{-1}

Reaction 2:

\text{N}_2\text{O}_4(\text{g}) \rightleftharpoons 2\text{NO}_2(\text{g}) \quad \Delta H = +57\,\text{kJ}\,\text{mol}^{-1}

The following changes can be applied independently to each system:

1. increasing the total pressure
2. increasing the temperature
3. decreasing the temperature

Assuming all other conditions remain constant, which of these changes will result in an increase in the equilibrium yield of products for Reaction 1 AND a decrease in the equilibrium yield of products for Reaction 2?

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

Answer: D

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Question 9

1 mark

A sample of a hydrated metal sulfate

MSO_4 \cdot nH_2O

is heated until all the water of crystallisation is removed. The mass of the sample is found to decrease by

51.22\%

.

In the anhydrous residue, the mass of the metal

M

is

37.5\%

of the total mass of oxygen atoms present.

What is the relative molar mass (

M_r

) of the hydrated salt?

(

A_r

values:

H = 1.0

;

O = 16.0

;

S = 32.0

)

A.120
B.180
C.210
D.246
E.278

Answer: D

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Question 10

1 mark

A sealed container contains a mixture of

1.10\,\text{g}

of carbon dioxide gas,

\text{CO}_2

, and

0.80\,\text{g}

of methane gas,

\text{CH}_4

. What is the total number of atoms present in this mixture?

(Take Avogadro's number as

6.0 \times 10^{23}\,\text{mol}^{-1}

.

A_r

values:

\text{H} = 1.0, \text{C} = 12.0, \text{O} = 16.0

)

A. $4.50 \times 10^{22}$
B. $1.50 \times 10^{23}$
C. $1.80 \times 10^{23}$
D. $1.95 \times 10^{23}$
E. $2.10 \times 10^{23}$

Answer: D

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Question 11

1 mark

Magnesium reacts with oxygen gas to form magnesium oxide according to the following balanced equation:

2\text{Mg}(\text{s}) + \text{O}_2(\text{g}) \rightarrow 2\text{MgO}(\text{s})

A student reacts

1.2\,\text{kg}

of magnesium ribbon with an excess of oxygen gas.

What is the amount, in moles, of oxygen molecules (

\text{O}_2

) that react with this mass of magnesium?

(

A_r

value:

\text{Mg} = 24

)

A. $0.025\,\text{mol}$
B. $2.5\,\text{mol}$
C. $25\,\text{mol}$
D.50 mol
E.100 mol

Answer: C

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Question 12

1 mark

A

4.50 \text{ g}

sample of a compound contains

1.20 \text{ g}

of carbon and

0.10 \text{ g}

of hydrogen, with the remainder being oxygen.

The relative molecular mass (

M_r

) of the compound is

90

.

What is the molecular formula of the compound?

(

A_r

values: C = 12; H = 1; O = 16)

A. $CHO_2$
B. $CH_2O$
C. $C_2H_2O_4$
D. $C_3H_6O_3$
E. $C_4H_4O_8$

Answer: C

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Question 13

1 mark

Calcium carbide (

CaC_2

) reacts with water to produce acetylene gas (

C_2H_2

) and calcium hydroxide (

Ca(OH)_2

) according to the following balanced chemical equation:

CaC_2(s) + 2H_2O(l) \rightarrow Ca(OH)_2(aq) + C_2H_2(g)

A student adds

1.60

g of

CaC_2

to

0.54

g of water. Which of the following statements about this reaction is/are correct?

1 Water is the limiting reactant.

2 The mass of acetylene gas produced is

0.65

g.

3 The mass of

CaC_2

that remains unreacted is

0.64

g.

(

A_r

values:

Ca = 40; C = 12; O = 16; H = 1.0

)

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

Answer: D

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Question 14

1 mark

A

3.20\,\text{g}

sample of an oxide of iron reacts completely with an excess of carbon monoxide (

\text{CO}

). The only products formed are iron metal and carbon dioxide (

\text{CO}_2

). The reaction produces

1.44\,\text{dm}^3

of carbon dioxide gas, measured at room temperature and pressure (RTP).

Which of the following is the correctly balanced equation for this reaction?

(

A_r

values:

\text{C} = 12

;

\text{O} = 16

;

\text{Fe} = 56

. Assume that

1\,\text{mol}

of gas occupies

24\,\text{dm}^3

at RTP.)

A. $\text{FeO} + \text{CO} \rightarrow \text{Fe} + \text{CO}_2$
B. $\text{Fe}_3\text{O}_4 + 4\text{CO} \rightarrow 3\text{Fe} + 4\text{CO}_2$
C. $\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2$
D. $\text{Fe}_2\text{O}_3 + \text{CO} \rightarrow 2\text{FeO} + \text{CO}_2$
E. $\text{Fe}_3\text{O}_4 + \text{CO} \rightarrow 3\text{FeO} + \text{CO}_2$

Answer: C

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Question 15

1 mark

A student titrates a

25.0\text{ cm}^3

sample of sulfuric acid,

H_2SO_4(aq)

, of unknown concentration with

0.100\text{ mol dm}^{-3}

sodium hydroxide,

NaOH(aq)

. The balanced equation for the neutralisation reaction is:

H_2SO_4(aq) + 2NaOH(aq) \rightarrow Na_2SO_4(aq) + 2H_2O(l)

Exactly

20.0\text{ cm}^3

of the sodium hydroxide solution is required to reach the end point. What is the concentration of the sulfuric acid?

A.0.0200 mol dm⁻³
B.0.0400 mol dm⁻³
C.0.0500 mol dm⁻³
D.0.0800 mol dm⁻³
E.0.160 mol dm⁻³

Answer: B

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Question 16

1 mark

The following chemical equation represents the reaction between lead(II) oxide and carbon in a smelting process:

2\mathrm{PbO} + \mathrm{C} ightarrow 2\mathrm{Pb} + \mathrm{CO}_2

Based on the gain and loss of oxygen, which of the following statements is correct?

A. $\mathrm{PbO}$ is oxidized because it gains oxygen.
B. $\mathrm{C}$ is reduced because it gains oxygen.
C. $\mathrm{PbO}$ is reduced because it loses oxygen.
D. $\mathrm{C}$ is oxidized because it loses oxygen.
E.Both $\mathrm{PbO}$ and $\mathrm{C}$ are reduced during the reaction.

Answer: C

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Question 17

1 mark

Which of the following chemical reactions involves the **reduction** (gain of electrons) of at least one species?

1.

2\text{Na} + \text{Cl}_2 \rightarrow 2\text{NaCl}

2.

\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}

3.

\text{AgNO}_3 + \text{KI} \rightarrow \text{AgI} + \text{KNO}_3

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

Answer: C

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Question 18

1 mark

The following unbalanced chemical equation represents the redox reaction between phosphorus and nitric acid:

xP_4 + yHNO_3 + zH_2O \rightarrow wH_3PO_4 + vNO

What is the value of the coefficient

y

when the equation is balanced using the smallest possible whole numbers?

A.4
B.5
C.10
D.12
E.20

Answer: E

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Question 19

1 mark

Phosphorous acid (

H_3PO_3

) is unstable and, when heated, it undergoes a disproportionation reaction to produce phosphoric acid (

H_3PO_4

) and phosphine gas (

PH_3

).

The unbalanced equation for this process is shown below:

aH_3PO_3 ightarrow bH_3PO_4 + cPH_3

What is the simplest integer ratio

b:c

in the balanced equation?

A.1:1
B.1:3
C.2:1
D.3:1
E.3:2

Answer: D

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Question 20

1 mark

The following displacement reaction occurs when chlorine gas is bubbled through an aqueous solution of potassium bromide:

\text{Cl}_2(g) + 2\text{KBr}(aq) \rightarrow 2\text{KCl}(aq) + \text{Br}_2(aq)

Which of the following statements about this reaction is correct?

A. $\text{Cl}_2$ is the reducing agent because its oxidation state decreases.
B. $\text{KBr}$ is the oxidising agent because the oxidation state of bromine increases.
C. $\text{Cl}_2$ is the oxidising agent because its oxidation state decreases.
D. $\text{Br}^-$ ions are the reducing agent because they gain electrons.
E.Potassium ions are the reducing agent because they lose electrons.

Answer: C

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Question 21

1 mark

An element

X

is in Period 3 and Group 2 of the Periodic Table. An element

Y

is in Period 2 and Group 17 of the Periodic Table. Which of the following correctly identifies the formula of the compound formed when

X

reacts with

Y

, and the type of bonding that occurs between them?

A.Formula: $XY$ ; Bonding: ionic
B.Formula: $X_2Y$ ; Bonding: ionic
C.Formula: $XY_2$ ; Bonding: ionic
D.Formula: $XY_2$ ; Bonding: covalent
E.Formula: $X_2Y$ ; Bonding: covalent

Answer: C

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Question 22

1 mark

Element

M

is a metal in Group 2 of the Periodic Table. It reacts with sulfuric acid to form an anhydrous salt with the formula

MSO_4

, containing the

SO_4^{2-}

ion. This salt has a relative formula mass (

M_r

) of 136.

Element

X

is a non-metal in Group 17 of the Periodic Table and is in the same period as

M

.

What is the relative formula mass (

M_r

) of the most stable ionic compound formed between elements

M

and

X

?

(

A_r

values:

O = 16

;

Mg = 24

;

S = 32

;

Cl = 35.5

;

Ca = 40

;

Br = 80

)

A.95
B.111
C.120
D.184
E.200

Answer: E

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Question 23

1 mark

Which of the following statements correctly explains the trends in metallic bonding and physical properties for the elements lithium (

Li

), sodium (

Na

), and magnesium (

Mg

)?

(Atomic numbers:

Li = 3, Na = 11, Mg = 12

)

A. $Mg$ has a higher melting point than $Na$ because the $Mg^{2+}$ ion has a higher charge and a smaller ionic radius than the $Na^{+}$ ion, leading to stronger electrostatic attractions between the cations and the delocalised electrons.
B. $Na$ has a higher melting point than $Li$ because $Na$ has more electron shells, which increases the total number of electrons available to form the delocalised 'sea'.
C.The electrical conductivity of Group 1 metals increases significantly from $Li$ to $Na$ because the larger atomic radius of $Na$ reduces the nuclear attraction on the delocalised electrons, allowing them to flow more freely.
D. $Mg$ has a lower melting point than $Na$ because the $2+$ charge of the $Mg^{2+}$ ions causes greater electrostatic repulsion between adjacent cations within the giant metallic lattice.
E.The metallic bond strength in Group 1 increases from $Li$ to $Na$ because the increase in nuclear charge ( $Z$ ) more than compensates for the increase in the distance between the nucleus and the delocalised electrons.

Answer: A

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Question 24

1 mark

The boiling points and properties of three substances,

X

,

Y

, and

Z

, are shown in the table below:

| Substance | Boiling point | Description |
| :--- | :--- | :--- |
|

X

|

-161\ ^\circ\text{C}

| non-polar;

10

electrons per molecule |
|

Y

|

-42\ ^\circ\text{C}

| non-polar;

26

electrons per molecule |
|

Z

|

+78\ ^\circ\text{C}

| polar;

26

electrons per molecule; contains an

-\text{OH}

group |

Which of the following statements correctly explain(s) these data?

1 The higher boiling point of

Y

compared to

X

is due to

Y

having more electrons, which results in stronger London (instantaneous dipole-induced dipole) forces
2 The higher boiling point of

Z

compared to

Y

is due to the presence of hydrogen bonding between molecules of

Z

3 When substance

Z

boils, the

\text{O}-\text{H}

covalent bonds within the molecules are broken

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

Answer: C

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Question 25

1 mark

A pure substance is tested and its properties are recorded below:

- State at room temperature: solid
- Melting point:

734^\circ\text{C}

- Electrical conductivity when solid: none
- Electrical conductivity when molten: good

Which of the following substances could be the identity of this sample?

A.graphite
B.iodine
C.copper
D.potassium bromide
E.silicon dioxide

Answer: D

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Question 26

1 mark

Consider the following statements regarding the physical and chemical properties of elements in Group 1 (alkali metals), Group 17 (halogens), and Group 18 (noble gases):

1. For any given period in the Periodic Table, the element in Group 18 has the highest first ionisation energy.
2. When

1.0\,\text{g}

of lithium and

1.0\,\text{g}

of sodium are each reacted separately with an excess of water, the volume of hydrogen gas produced by the lithium (measured at the same temperature and pressure) is more than twice the volume produced by the sodium.
3. The boiling point of the halogens increases down the group because the covalent bond between the atoms in the

X_2

molecules becomes stronger as the atomic number increases.

Which of the statements is/are correct?
(Assume that all reactions go to completion and behave ideally. Relative atomic masses:

\text{Li} = 6.9

,

\text{Na} = 23.0

.)

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

Answer: A

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Question 27

1 mark

In two separate experiments, a

1.4\text{ g}

sample of lithium and a

4.6\text{ g}

sample of sodium are added to excess water. Both reactions are carried out at the same temperature and pressure.

Which of the following correctly compares the vigour of the reaction and the volume of hydrogen gas produced in each case?

(

A_r

values:

H = 1

;

Li = 7

;

Na = 23

;

O = 16

)

A.Sodium reacts more vigorously and produces a greater volume of hydrogen gas than lithium.
B.Sodium reacts more vigorously and produces a smaller volume of hydrogen gas than lithium.
C.Sodium reacts more vigorously and both reactions produce the same volume of hydrogen gas.
D.Lithium reacts more vigorously and both reactions produce the same volume of hydrogen gas.
E.Lithium reacts more vigorously and produces a greater volume of hydrogen gas than sodium.

Answer: C

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Question 28

1 mark

A

0.10\,\text{mol}

sample of a halogen

X_2

reacts completely with an excess of magnesium to form

9.5\,\text{g}

of a compound with the formula

MgX_2

.

Aqueous

X_2\text{(aq)}

is then added to three separate test tubes containing aqueous solutions of sodium fluoride (

NaF

), sodium bromide (

NaBr

), and sodium iodide (

NaI

).

Which row in the following table correctly identifies the element

X

and the solutions (from the three tested) in which a displacement reaction occurs?

| | identity of

X

| displacement reaction(s) with: |
|---|---|---|
| A | chlorine |

NaBr\text{(aq)}

and

NaI\text{(aq)}

only |
| B | chlorine |

NaF\text{(aq)}

only |
| C | bromine |

NaI\text{(aq)}

only |
| D | bromine |

NaF\text{(aq)}

and

NaI\text{(aq)}

only |
| E | fluorine |

NaBr\text{(aq)}

and

NaI\text{(aq)}

only |

(

A_r

values:

\text{F} = 19.0

;

\text{Mg} = 24.0

;

\text{Cl} = 35.5

;

\text{Br} = 80.0

)

A. $X = \text{chlorine}$ ; displacement in $NaBr\text{(aq)}$ and $NaI\text{(aq)}$ only
B. $X = \text{chlorine}$ ; displacement in $NaF\text{(aq)}$ only
C. $X = \text{bromine}$ ; displacement in $NaI\text{(aq)}$ only
D. $X = \text{bromine}$ ; displacement in $NaF\text{(aq)}$ and $NaI\text{(aq)}$ only
E. $X = \text{fluorine}$ ; displacement in $NaBr\text{(aq)}$ and $NaI\text{(aq)}$ only

Answer: A

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Question 29

1 mark

Consider the following four procedures used to isolate specific elements:

1. Fractional distillation of liquid air to obtain oxygen,

\text{O}_2

.
2. Electrolysis of molten lithium chloride,

\text{LiCl}

, to obtain lithium metal,

\text{Li}

.
3. Heating zinc oxide,

\text{ZnO}

, with carbon to obtain zinc metal,

\text{Zn}

.
4. Sublimation of a mixture of sand and iodine to obtain pure iodine crystals,

\text{I}_2

.

According to the principle that chemical processes are required to displace constituent elements from their compounds, which of these procedures are classified as chemical processes?

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

Answer: B

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Question 30

1 mark

A student uses paper chromatography to analyze three liquid food dyes,

J

,

K

, and

L

. The solvent front moved

12.0\,\text{cm}

from the baseline. The results recorded for the centres of the spots are as follows:

- Dye

J

: a single spot at

9.0\,\text{cm}

from the baseline.
- Dye

K

: two spots at

3.0\,\text{cm}

and

6.0\,\text{cm}

from the baseline.
- Dye

L

: a single spot at

6.0\,\text{cm}

from the baseline.

Which of the following statements is/are correct?

1. Dye

K

is a pure substance.
2. Dye

K

contains dye

L

.
3. The

R_f

value of the spot produced by dye

J

is

0.75

.

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

Answer: E

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ESAT Mock Chemistry Esat-chem-bank-2

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