Chemistry Mock Exam

[21 Aug] Chemistry 2025 Mock Exam

Question Paper

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Which is correct for the complex ion in [Fe(H2O)5Cl]SO4?

A

B

C

D

Question 2

Urea, (H2N)2CO, 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.

2NH3(g) + CO2(g) ⇌ (H2N)2CO(g) + H2O(g) Δ_H_ < 0

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

[2]

2. Suggest how the percentage of nitrogen affects the cost of transport of fertilizers giving a reason.

[1]

3. The structural formula of urea is shown.

Predict the electron domain and molecular geometries at the nitrogen and carbon atoms, applying the VSEPR theory.

[3]

4. Urea can be made by reacting potassium cyanate, KNCO, with ammonium chloride, [2]

6. Predict, with a reason, the effect on the equilibrium constant, _K_c, when the temperature is increased.

[1]

7. Determine an approximate order of magnitude for _K_c, using sections 1 and 2 of the data booklet. Assume Δ_G_Θfor the forward reaction is approximately +50 kJ at 298 K.

[2]

8. Suggest one reason why urea is a solid and ammonia a gas at room temperature. [1]

9. Sketch two different hydrogen bonding interactions between ammonia and water. [2]

10.The combustion of urea produces water, carbon dioxide and nitrogen.

Formulate a balanced equation for the reaction.

[2]

11.Calculate the maximum volume of CO2, in cm3, produced at STP by the combustion of 0.600 g of urea, using sections 2 and 6 of the data booklet.

[1]

12.Describe the bond formation when urea acts as a ligand in a transition metal complex ion.

[2]

13.The C–N bonds in urea are shorter than might be expected for a single C–N bond.

Suggest, in terms of electrons, how this could occur.

[1]

14.The mass spectrum of urea is shown below. [2]

Identify the species responsible for the peaks at m/z = 60 and 44.

15.The IR spectrum of urea is shown below. [2]

Identify the bonds causing the absorptions at 3450 cm−1 and 1700 cm−1 using section 26 of the data booklet.

16.Predict the number of signals in the 1H NMR spectrum of urea. [1]

17.Predict the splitting pattern of the 1H NMR spectrum of urea. [1]

18.Outline why TMS (tetramethylsilane) may be added to the sample to carry out 1H NMR spectroscopy and why it is particularly suited to this role.

[2]

Question 3

Which element is found in the 4th group, 6th period of the periodic table?

A

Selenium

B

Lead

C

Chromium

D

Hafnium

Question 4

What is the charge on the iron(III) complex ion in [Fe(OH)2(H2O)4]Br?

A

0

B

1+

C

2+

D

3+

Which is a d-block element?

A

Ca

B

Cf

C

Cl

D

Co

Question 6

Cobalt forms the transition metal complex [Co(NH3)4 (H2O)Cl]Br.

Trends in physical and chemical properties are useful to chemists.

1. Explain why the melting points of the group 1 metals (Li → Cs) decrease down

thegroup whereas the melting points of the group 17 elements (F → I) increase down thegroup.

[3]

2. State the shape of the complex ion. [1]

3. Deduce the charge on the complex ion and the oxidation state of cobalt. [2]

Which element is a lanthanide?

A

Hf

B

Tb

C

U

D

Y

Question 8

Which of the following would have the same numerical value for all elements in the same period?

A

Highest energy levels occupied

B

Energy sub-levels occupied

C

Orbitals occupied

D

Valence electrons

Question 9

What is the overall charge, x, of the chromium (III) complex?

[Cr(H2O)4Cl2]x

A

0

B

1+

C

2−

D

3+

Question 10

Which electrons are removed from iron (Z = 26) to form iron(II)?

A

two 3d electrons

B

two 4s electrons

C

one 4s electron and one 3d electron

D

two 4p electrons

Which electron configuration is that of a transition metal atom in the ground state?

A

[Ne]3s23p64s1

B

[Ar]3d9

C

1s22s22p63s23p64s23d104p2

D

[Ar]4s13d5

Question 12

Which describes an atom of bismuth, Bi (Z = 83)?

A

B

C

D

When heated in air, magnesium ribbon reacts with oxygen to form magnesium oxide.

The reaction in (a)(i) was carried out in a crucible with a lid and the following data was recorded:

Mass of crucible and lid = 47.372 ±0.001 g

Mass of crucible, lid and magnesium ribbon before heating = 53.726 ±0.001 g Mass of crucible, lid and product after heating = 56.941 ±0.001 g

When magnesium is burnt in air, some of it reacts with nitrogen to form magnesium nitride according to the equation:

3 Mg (s) + N2 (g) → Mg3N2 (s)

The presence of magnesium nitride can be demonstrated by adding water to the product.

It is hydrolysed to form magnesium hydroxide and ammonia.

Most nitride ions are 14N3–.

1. Write a balanced equation for the reaction that occurs.

a(i).

[1]

2. State the block of the periodic table in which magnesium is located.

a(ii).

[1]

3. Identify a metal, in the same period as magnesium, that does not form a basic oxide.

a(iii).

[1]

4. Calculate the amount of magnesium, in mol, that was used.

b(i).

[1]

5. Determine the percentage uncertainty of the mass of product after heating.

b(ii).

[2]

6. Assume the reaction in (a)(i) is the only one occurring and it goes to completion, but some product has been lost from the crucible. Deduce the percentage yield of magnesium oxide in the crucible.

b(iii).

[2]

7. Evaluate whether this, rather than the loss of product, could explain the yield found in (b)(iii).

c(i).

[1]

8. Suggest an explanation, other than product being lost from the crucible or reacting with nitrogen, that could explain the yield found in (b)(iii).

c(ii).

[1]

9. Calculate coefficients that balance the equation for the following reaction.

__ Mg3N2 (s) + __ H2O (l) → __ Mg(OH)2 (s) + __ NH3 (aq) d(i).

[1]

10.Determine the oxidation state of nitrogen in Mg3N2 and in NH3.

d(ii).

[1]

11.Deduce, giving reasons, whether the reaction of magnesium nitride with water is an acid–base reaction, a redox reaction, neither or both.

[2]

d(iii).

12.State the number of subatomic particles in this ion.

e(i).

[1]

13.Some nitride ions are 15N3–. State the term that describes the relationship between 14N3– and 15N3–.

e(ii).

[1]

14.The nitride ion and the magnesium ion are isoelectronic (they have the same electron configuration). Determine, giving a reason, which has the greater ionic radius.

e(iii).

[1]

15.Suggest two reasons why atoms are no longer regarded as the indivisible units of matter.

[2]

Question 14

Ammonia is a stronger ligand than water. Which is correct when concentrated aqueous ammoniasolution is added to dilute aqueous copper(II) sulfate solution?

A

The d-orbitals in the copper ion split.

B

There is a smaller splitting of the d-orbitals.

C

Ammonia replaces water as a ligand.

D

The colour of the solution fades.

16.State the types of bonding in magnesium, oxygen and magnesium oxide, and how the valence electrons produce these types of bonding.

[4]

Bromine can form the bromate(V) ion, BrO3−.

1. State the electron configuration of a bromine atom. [1]

2. Sketch the orbital diagram of the valence shell of a bromine atom (ground state) on the energy axis provided. Use boxes to represent orbitals and arrows to represent electrons.

[1]

3. Draw two Lewis (electron dot) structures for BrO3−. [2]

4. Determine the preferred Lewis structure based on the formal charge on the bromine atom, giving your reasons.

[2]

5. Predict, using the VSEPR theory, the geometry of the BrO3− ion and the O−Br−O bond angles.

[3]

6. Bromate(V) ions act as oxidizing agents in acidic conditions to form bromide ions.

Deduce the half-equation for this reduction reaction.

[2]

7. Bromate(V) ions oxidize iron(II) ions, Fe2+, to iron(III) ions, Fe3+.

Deduce the equation for this redox reaction.

[1]

8. Calculate the standard Gibbs free energy change, Δ_G_Θ, in J, of the redox reaction in (ii), using sections 1 and 24 of the data booklet.

_E_Θ (BrO3− / Br−) = +1.44 V

[2]

9. State and explain the magnetic property of iron(II) and iron(III) ions. [2]

Ammonia is soluble in water and forms an alkaline solution:

NH3 (g) + H2O (l) ⇌ NH4+ (aq) + HO– (aq)

1. State the relationship between NH4+ and NH3 in terms of the Brønsted–Lowry theory.

[1]

2. Determine the concentration, in mol dm–3, of the solution formed when 900.0 dm3 of NH3 (g) at 300.0 K and 100.0 kPa, is dissolved in water to form 2.00 dm3 of solution. Use sections 1 and 2 of the data booklet.

[2]

3. Calculate the concentration of hydroxide ions in an ammonia solution with pH = 9.3.

Use sections 1 and 2 of the data booklet.

c(i).

[1]

4. Calculate the concentration, in mol dm–3, of ammonia molecules in the solution with pH = 9.3. Use section 21 of the data booklet.

c(ii).

[2]

5. An aqueous solution containing high concentrations of both NH3 and NH4+ acts asan acid-base buffer solution as a result of the equilibrium:

NH3 (aq) + H+ (aq) ⇌ NH4+ (aq)

Referring to this equilibrium, outline why adding a small volume of strong acidwould leave the pH of the buffer solution almost unchanged.

c(iii).

[2]

6. Magnesium salts form slightly acidic solutions owing to equilibria such as:

Mg2+ (aq) + H2O (l) ⇌ Mg(OH)+ (aq) + H+ (aq)

Comment on the role of Mg2+ in forming the Mg(OH)+ ion, in acid-base terms.

[2]

Question 17

Which complex ion contains a central ion with an oxidation state of +3?

A

[PtCl6]2−

B

[Cu(H2O)4(OH)2]

C

[Ni(NH3)4(H2O)2]2+

D

[Co(NH3)4Cl2]+

7. Mg(OH)+ is a complex ion, but Mg is not regarded as a transition metal. Contrast Mg with manganese, Mn, in terms of one characteristic chemical property of transition metals, other than complex ion formation.

[2]

Which property increases down Group 1, the alkali metals?

A

Atomic radius

B

Electronegativity

C

First ionization energy

D

Melting point

Question 19

Rhenium, Re, was the last element with a stable isotope to be isolated.

Before its isolation, scientists predicted the existence of rhenium and some of its properties.

One chloride of rhenium has the empirical formula ReCl3.

Rhenium forms salts containing the perrhenate(VII) ion, ReO4−.

1. The stable isotope of rhenium contains 110 neutrons.

State the nuclear symbol notation Z A X for this isotope.

[1]

2. Suggest the basis of these predictions.

b(i).

[2]

3. A scientist wants to investigate the catalytic properties of a thin layer of rhenium metal on a graphite surface.

Describe an electrochemical process to produce a layer of rhenium on graphite.

b(ii).

[2]

4. Predict two other chemical properties you would expect rhenium to have, given its position in the periodic table.

b(iii).

[2]

5. Describe how the relative reactivity of rhenium, compared to silver, zinc, and copper, can be established using pieces of rhenium and solutions of these metal sulfates.

[2]

6. State the name of this compound, applying IUPAC rules. [1]

predicted. Refer to section 6 of the data booklet.

e(i).

9. Deduce the coefficients required to complete the half-equation.

ReO4− (aq) + ____H+ (aq) + ____e− ⇌ [Re(OH)2]2+ (aq) + ____H2O (l) Eθ = +0.36 V

e(ii).

[1]

10.Predict, giving a reason, whether the reduction of ReO4− to [Re(OH)2]2+ would oxidize Fe2+ to Fe3+ in aqueous solution. Use section 24 of the data booklet.

e(iii).

[1]

Question 20

Millerite, a nickel sulfide mineral, is an important source of nickel. The first step in extractingnickel is to roast the ore in air.

The reaction for the formation of liquid tetracarbonylnickel is shown below:

Ni(s) + 4 CO(g) → Ni(CO ) 4 (l)

1. Formulate an equation for the oxidation of nickel(II) sulfide to nickel(II) oxide. [1]

2. The nickel obtained from another ore, nickeliferous limonite, is contaminated with iron.Both nickel and iron react with carbon monoxide gas to form gaseous

complexes,tetracarbonylnickel, Ni(CO ) 4 (g) , and pentacarbonyliron, Fe(CO ) 5 (g) . Suggest why thenickel can be separated from the iron successfully using carbon monoxide.

[1]

3. Calculate the standard entropy change, Δ S θ , of the reaction, in J K − 1 , using thevalues given.

[2]

4. Calculate a value for Δ H θ in kJ. [1]

Question 21

The concentration of a solution of a weak acid, such as ethanedioic acid, can be determined

by titration with a standard solution of sodium hydroxide, NaOH (aq).

6. Suggest why experiments involving tetracarbonylnickel are very hazardous. [1]

1. 5.00 g of an impure sample of hydrated ethanedioic acid, (COOH)2•2H2O, was dissolved in water to make 1.00 dm3 of solution. 25.0 cm3 samples of this solution were titrated against a 0.100 mol dm-3 solution of sodium hydroxide using a suitable indicator.

(COOH)2 (aq) + 2NaOH (aq) → (COONa)2(aq) + 2H2O (l) The mean value of the titre was 14.0 cm3.

(i) Suggest a suitable indicator for this titration. Use section 22 of the data booklet.

(ii) Calculate the amount, in mol, of NaOH in 14.0 cm3 of 0.100 mol dm-3 solution.

(iii) Calculate the amount, in mol, of ethanedioic acid in each 25.0 cm3 sample.

(iv) Determine the percentage purity of the hydrated ethanedioic acid sample.

[6]

2. Draw the Lewis (electron dot) structure of the ethanedioate ion, –OOCCOO–. [1]

3. Outline why all the C–O bond lengths in the ethanedioate ion are the same length and suggest a value for them. Use section 10 of the data booklet.

[2]

4. Explain how ethanedioate ions act as ligands. [2]

Question 22

Which element is in the p-block?

A

Pb

B

Pm

C

Pt

D

Pu

An acidic sample of a waste solution containing Sn2+(aq) reacted completely with K2Cr2O7solution to form Sn4+(aq).

1. Identify one organic functional group that can react with acidified K2Cr2O7(aq). [1]

2. Corrosion of iron is similar to the processes that occur in a voltaic cell. The initialsteps involve the following half-equations:

Fe2+(aq) + 2e– ⇌ Fe(s)

1 2 O2(g) + H2O(l) + 2e– ⇌ 2OH–(aq)

Calculate E θ, in V, for the spontaneous reaction using section 24 of thedata booklet.

[1]

3. Calculate the Gibbs free energy, Δ_G_ θ, in kJ, which is released by the corrosion of1 mole of iron. Use section 1 of the data booklet.

[2]

4. Explain why iron forms many different coloured complex ions. [3]

5. Zinc is used to galvanize iron pipes, forming a protective coating. Outline how thisprocess prevents corrosion of the iron pipes.

[1]

Question 24

Which species has the same electron configuration as argon?

A

Br−

B

Ca2+

C

Al3+

D

Si4+

Iron may be extracted from iron (II) sulfide, FeS.

Iron (II) sulfide, FeS, is ionically bonded.

The first step in the extraction of iron from iron (II) sulfide is to roast it in air to form iron (III) oxide and sulfur dioxide.

1. Outline why metals, like iron, can conduct electricity. [1]

2. Justify why sulfur is classified as a non-metal by giving two of its chemical properties.

[2]

3. Describe the bonding in this type of solid.

c(i).

[2]

4. State the full electron configuration of the sulfide ion.

c(ii).

[1]

5. Outline, in terms of their electronic structures, why the ionic radius of the sulfide ion is greater than that of the oxide ion.

c(iii).

[1]

6. Suggest why chemists find it convenient to classify bonding into ionic, covalent and metallic.

c(iv).

[1]

7. Write the equation for this reaction.

d(i).

[1]

8. Deduce the change in the oxidation state of sulfur.

d(ii).

[1]

Question 26

Which is an f-block element?

A

Sc

B

Sm

C

Sn

D

Sr

9. Suggest why this process might raise environmental concerns.

d(iii).

[1]

10.Explain why the addition of small amounts of carbon to iron makes the metal harder. [2]

Which describes an atom of bismuth, Bi (Z = 83)?

A

B

C

D

Question 28

The emission spectrum of an element can be used to identify it.

1. Hydrogen spectral data give the frequency of 3.28 × 1015 s−1 for its convergencelimit.

Calculate the ionization energy, in J, for a single atom of hydrogen using sections1 and 2 of the data booklet.

[1]

2. Calculate the wavelength, in m, for the electron transition corresponding to thefrequency in (a)(iii) using section 1 of the data booklet.

[1]

3. Deduce any change in the colour of the electrolyte during electrolysis. [1]

4. Deduce the gas formed at the anode (positive electrode) when graphite is used inplace of copper.

[1]

5. Explain why transition metals exhibit variable oxidation states in contrast to alkalimetals.

[2]

Which of these statements are correct?

I.Zinc is not a transition element.

II. Ligands are Lewis bases.

III. Manganese(II) chloride is paramagnetic.

A

I and II only

B

I and III only

C

II and III only

D

I, II and III

Question 30

Iron may be extracted from iron (II) sulfide, FeS.

Iron (II) sulfide, FeS, is ionically bonded.

The first step in the extraction of iron from iron (II) sulfide is to roast it in air to form iron (III) oxide and sulfur dioxide.

1. Outline why metals, like iron, can conduct electricity. [1]

2. Justify why sulfur is classified as a non-metal by giving two of its chemical properties.

[2]

3. Sketch the first eight successive ionisation energies of sulfur. [2]

compound.

d(ii).

6. State the full electron configuration of the sulfide ion.

d(iii).

[1]

7. Outline, in terms of their electronic structures, why the ionic radius of the sulfide ion is greater than that of the oxide ion.

d(iv).

[1]

8. Suggest why chemists find it convenient to classify bonding into ionic, covalent and metallic.

d(v).

[1]

9. Write the equation for this reaction.

e(i).

[1]

10.Deduce the change in the oxidation state of sulfur.

e(ii).

[1]

11.Suggest why this process might raise environmental concerns.

e(iii).

[1]

12.Explain why the addition of small amounts of carbon to iron makes the metal harder. [2]

Question 31

How do the following properties change down Group 17 of the periodic table?

A

B

C

D

What is the oxidation state of the metal ion and charge of the complex ion in [Co(NH3)4Cl2]Cl?

A

B

C

D

Question 33

Titanium and vanadium are consecutive elements in the first transition metal series.

TiC l 4 reacts with water and the resulting titanium(IV) oxide can be used as a smoke screen.

1. Describe the bonding in metals. [2]

2. Titanium exists as several isotopes. The mass spectrum of a sample of titanium gave the following data:

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

[2]

3. State the number of protons, neutrons and electrons in the 22 48 Ti atom. [1]

5. Suggest why the melting point of vanadium is higher than that of titanium. [1]

6. Sketch a graph of the first six successive ionization energies of vanadium on theaxes provided.

[1]

7. Explain why an aluminium-titanium alloy is harder than pure aluminium. [2]

8. Describe, in terms of the electrons involved, how the bond between a ligand and acentral metal ion is formed.

[1]

9. Outline why transition metals form coloured compounds. [4]

10.State the type of bonding in potassium chloride which melts at 1043 K. [1]

11.A chloride of titanium, TiC l 4 , melts at 248 K. Suggest why the melting point is so much lower than that of KCl.

[1]

12.Formulate an equation for this reaction. [2]

Question 34

Which of these ions are likely to be paramagnetic?

I. Ti3+

II. Cr3+

III. Fe3+

A

I and II only

B

I and III only

C

II and III only

D

I, II and III

1