[2 Dec] Chemistry (New

syllabus) Mock Exam

Question Paper

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Question 1

Sodium peroxide, N a2 O2 , is formed by the reaction of sodium oxide with oxygen.

​ ​

2N a2 O(s) + O2 (g) → 2N a2 O2 (s)

​ ​ ​ ​

Calculate the percentage yield of sodium peroxide if 5.00 g of sodium oxide [2]
produces 5.50 g of sodium peroxide.

Question 2

Describe the structure of the nuclear atom, including the relative masses and [4]
charges of protons, neutrons, and electrons.
Question 3

An acidic sample of a waste solution containing Sn2+ (aq) reacted completely

with K2 C r2 O7 solution to form Sn4+ (aq).
​ ​ ​

1. Calculate the percentage uncertainty for the mass of K2 C r2 O7 (s) from thegiven
​ ​ ​
[1]
data.

m(weight boat) = 1.090 ± 0.001 g

m(weight boat + K2 C r2 O7 (s)) = 14.329 ± 0.001 g
​ ​

2. The sample of K2 Cr2 O7 (s) in Part 1 was dissolved in distilled water to form
​ ​ ​
[1]
0.100 dm3solution. Calculate its molar concentration.

3. 10.0 cm3 of the waste sample required 13.24 cm3 of the K2Cr2O7 [2]
solution.Calculate the molar concentration of Sn2+(aq) in the waste sample.
Question 4

The thermal decomposition of dinitrogen monoxide occurs according to the

equation:

2 N2 O( g) → 2 N2 ( g) + O2 ( g)
​ ​ ​

The reaction can be followed by measuring the change in total pressure, at

constant temperature, with time.

1. Explain why, as the reaction proceeds, the pressure increases will increase. [2]

2. Outline, in terms of collision theory, how a decrease in pressure would affect the [2]
rate of reaction.
Question 5
Ammonia is produced by the Haber process according to the following reaction.
N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH is negative

1. Describe the behaviour of a buffer solution.

2. 20.0 cm³ of a known concentration of potassium hydroxide is titrated with a solution

of sulfuric acid. The graph for this titration is given below.

3. State and explain two methods, other than measuring pH, which could be used to
distinguish between 1.0 mol dm⁻³ solutions of sulfuric acid and acetic acid.

4. Predict the volume of acetic acid of the same concentration as the sulfuric acid in
(iii), required to neutralize 20.0 cm³ of this potassium hydroxide solution.

5. Calculate the concentration of the potassium hydroxide solution before the titration.

6. From the graph determine the volume of sulfuric acid required to neutralize the
potassium hydroxide and calculate the concentration of the sulfuric acid.

7. State an equation for the reaction between potassium hydroxide and sulfuric acid.

8. Sulfuric acid and ammonia may be used to make a buffer solution.

9. Explain why a 1.0 mol dm⁻³ solution of potassium hydroxide has a pH of 14

whereas 1.0 mol dm⁻³ ammonia solution has a pH of about 12. Use equations in
your answer.

10. Describe how you could prepare a buffer solution using 0.100 mol dm⁻³ solutions of
sulfuric acid and ammonia.
Question 6

A student determined the percentage of the active ingredient magnesium

hydroxide, Mg(OH)2 , in a 1.24 g antacid tablet.
​

The antacid tablet was added to 50.00 cm3 of 0.100 mol dm−3 sulfuric acid, which
was in excess.

1. Calculate the amount, in mol, of H2SO4. [1]

2. Formulate the equation for the reaction of H2SO4 with Mg(OH)2. [1]

3. The excess sulfuric acid required 20.80 cm3 of 0.1133 mol dm−3 NaOH for [1]
neutralization.

Calculate the amount of excess acid present.

4. Calculate the amount of H2SO4 that reacted with Mg(OH)2. [1]

5. Determine the mass of Mg(OH)2 in the antacid tablet. [2]

6. Calculate the percentage by mass of magnesium hydroxide in the 1.24 g antacid [1]
tablet to three significant figures.

Question 7

Describe the Aufbau principle, Hund's rule, and the Pauli exclusion principle and [6]
explain how they are used to determine the arrangement of electrons in atomic
orbitals.
Question 8

Chlorine undergoes many reactions. Chlorine gas reacts with water to produce
hypochlorous acid and hydrochloric acid.

Cl2 (g)+H2O (l)⇌HClO (aq)+HCl (aq)

1. State the full electron configuration of the chlorine atom. [1]

2. State, giving a reason, whether the chlorine atom or the chloride ion has a larger [1]
radius.

3. Outline why the chlorine atom has a smaller atomic radius than the sulfur atom. [2]

Question 9

This question deals with gases and liquids.

1. The mass of a gas sample is measured under certain conditions. List the variables [4]
that must be measured and show how these can be used to determine the molar
mass of the gas.

2. As a volatile liquid in an isolated container evaporates, its temperature drops. [2]

Account for this observation in terms of the behaviour of the molecules.

3. A small amount of a volatile liquid is added to a 50.0 cm3 evacuated container. [3]
Twice the amount of the same liquid is added to a second 50.0 cm3 evacuated
container, and separately to a 100 cm3 evacuated container. The three systems are
allowed to reach equilibrium at the same temperature, and some liquid remains in
each flask. Compare the pressure due to the vapour in the three containers and
explain your answer.
Question 10
A student conducts an experiment to study the relationship between pressure and
temperature for a fixed volume of gas to verify Gay-Lussac's Law, which states that
P ∝ T for an ideal gas. The student records the following data:

Temperature (°C) Pressure (kPa)

0 101

20 108

40 116

60 123

80 130

100 138

1. Convert the temperatures from ∘ C to Kelvin and plot a graph of P (pressure) on the [4]
y -axis versus T (temperature in Kelvin) on the x-axis.

2. From the graph, determine if there is a linear relationship between P and T . [4]
Calculate the slope of the line and explain its physical meaning in terms of Gay-
Lussac's Law.

3. Assume an uncertainty of ±1kPa for each pressure measurement. Calculate the [4]
effect of this uncertainty on the slope of the line, and discuss how it might affect the
verification of Gay-Lussac's Law.

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Question 11
Vanadium, another transition metal, has a number of different oxidation states.

1. Determine the oxidation state of vanadium in V2 O5 and V O 2+ .

​ ​
[2]

2. Formulate an equation for the reaction between V O 2+ (aq) and V 2+ (aq) in [1]
acidic solution to form V 3+ (aq).
Question 12

The table below shows data on the atomic radius, density, and ionization energy of
selected transition metals. Use the data to answer the questions that follow.

Metal Atomic Radius (pm) Density (g/cm3 ) First Ionization Energy (kJ/mol)

Sc 162 2.99 631

Fe 126 7.87 762

Ni 124 8.90 737

Cu 128 8.96 745

Zn 134 7.14 906

1. Describe the trend in atomic radius across these metals and explain how it relates [3]
to the strength of metallic bonding.

2. Explain the relationship between density and metallic bonding strength, using the [2]
metals Fe and Cu as examples.

3. Calculate the difference in first ionization energy between zinc (Zn) and scandium [3]
(Sc). Discuss briefly how ionization energy correlates with metallic bonding
strength.

Question 13
Methane, CH4, is a greenhouse gas.

Outline, in molecular terms, how methane molecules absorb infrared radiation [2]
Question 14
Urea, (H2 N )2 CO , is excreted by mammals and can be used as a fertilizer.
​ ​

Urea can also be made by the direct combination of ammonia and carbon dioxide
gases.

2N H3 (g) + CO2 (g) ⇌ (H2 N )2 CO(g) + H2 O(g)

​ ​ ​ ​ ​

ΔH < 0

1. Calculate the percentage by mass of nitrogen in urea to two decimal places using [2]
section 6 of the data booklet.

2. Suggest how the percentage of nitrogen affects the cost of transport of fertilizers [1]
giving a reason.
Question 15
This question is about compounds of sodium.

Sodium peroxide is used in diving apparatus to produce oxygen from carbon

dioxide.

2Na2O2 (s) + 2CO2 (g) → 2Na2CO3 (s) + O2 (g)

1. Describe the structure and bonding in solid sodium oxide. [2]

2. Write equations for the separate reactions of solid sodium oxide and solid [3]
phosphorus(V) oxide with excess water and differentiate between the solutions
formed.

1. Sodium oxide, Na2O:

2. Phosphorus(V) oxide, P4O10:

3. Differentiation:

3. Sodium peroxide, Na2O2, is formed by the reaction of sodium oxide with oxygen. [2]

2Na2O (s) + O2 (g) → 2Na2O2 (s)

Calculate the percentage yield of sodium peroxide if 5.00 g of sodium oxide

produces 5.50 g of sodium peroxide.
Question 16
A sample of an ideal gas is confined in a container with a movable piston. The gas
initially occupies a volume of 2.00 dm³ at a pressure of 100 kPa and a temperature
of 298 K. The gas is then heated and allowed to expand at constant pressure. The
final volume of the gas is measured at different temperatures as shown in the table
below.

Temperature (K) Volume (dm3 )

298 2.00

350 2.35

400 2.68

450 3.00

500 3.35

1. Using the ideal gas equation P V = nRT , calculate the number of moles of gas [3]
in the container when the temperature is 298 K , the pressure is 100 kPa , and the
3
volume is 2.00dm . (Use R = 8.31 J mol−1 K−1 ).

2. Using the data provided in the table, plot a graph of volume (dm³) against [3]
temperature (K), and determine whether the gas behaves according to Charles's
Law.

3. Using the trend observed in Part 2, predict the volume of the gas when the [2]
temperature reaches 550 K.

4. Explain how the ideal gas law assumes the behavior of gases and discuss [3]
whether the assumptions are likely to hold for this gas over the range of
temperatures provided in the table.
Question 17

Titanium is a transition metal.

TiCl4 reacts with water and the resulting titanium (IV) oxide can be used as a
smokescreen.

1. Titanium exists as several isotopes. The mass spectrum of a sample of titanium [2]
gavethe following data:

Mass number % abundance

46 7.98
47 7.32
48 73.99
​ ​ ​

49 5.46
50 5.25

Calculate the relative atomic mass of titanium to two decimal places.

2. State the number of protons, neutrons and electrons in the 48

22 T i atom.
​
[1]

3. State the full electron configuration of the 48

22 T i
​
2+
ion. [1]

Question 18

Describe the attributes of the nematic liquid crystal phase and the impact that an [3]
electric field has on it.

I. Shape of molecules:

II. Distribution:

III. Effect of electric field:

Question 19

1. State two characteristics of a homologous series. [2]

2. Describe a chemical test to distinguish between alkanes and alkenes, giving the [3]
result in each case.

3. Some alcohols are oxidized by heating with acidified potassium dichromate(VI). If [4]
oxidation does occur, identify the possible oxidation products formed by each of the
alcohols below. Indicate if no oxidation occurs.

Butan-1-ol

Butan-2-ol

2-methylpropan-2-ol