1.

Which subatomic particle determines the chemical properties of an

A. Proton B. Neutron C. Electron D. Nucleus

2. The mass number of an atom is equal to:

A. Number of protons only

B. Number of neutrons only

C. Number of electrons only

D. Sum of protons and neutrons

3. Which isotope contains 20 protons and 22 neutrons?

A. B. C. D.

4. What is the electron configuration of ?

A. 1s² 2s² 2p⁶ 3s² B. 1s² 2s² 2p⁶

C. 1s² 2s² 2p⁶ 3s¹ D. 1s² 2s² 2p⁵

5. Which technique is used to determine the relative atomic mass?

A. Infrared spectroscopy B. Mass spectrometry

C. Chromatography D. Colorimetry
6. Which of the following has the highest first ionisation energy?

A. Na B. Mg C. Al D. Si

7. Why does the first ionisation energy increase across a period?

A. Atomic radius increases

B. Nuclear charge decreases

C. Shielding increases

D. Nuclear charge increases

8. Which species is isoelectronic with neon?

A. B. C. D. All of the above

9. Order of sub-levels by increasing energy?

A. 1s < 2s < 2p < 3p < 3s

B. 1s < 2s < 3s < 2p < 3p

C. 1s < 2s < 2p < 3s < 3p

D. 1s < 3s < 2s < 2p < 3p

10. Which period contains 1s² 2s² 2p⁶ 3s² 3p⁴?

A. Period 2 B. Period 3 C. Period 4 D. Period 5

11. Which orbital can hold a maximum of 6 electrons?

12. What is the charge and mass of a neutron?

A. 0, 1 B. –1, 0 C. +1, 1 D. 0, 0

13. Which factor has the greatest effect on ionisation energy?

A. Atomic mass

B. Shielding

C. Number of neutrons

D. Electron-electron repulsion

14. In ionisation, which electron is removed first?

A. From the outermost shell

B. From the innermost shell

C. From the nucleus

D. Randomly selected

15. Which element has the lowest first ionisation energy in Period 3?

A. Na B. Mg C. Al D. Cl
---

🔹 Section B: Chemical Equilibria (15 questions)

16. In a reversible reaction at equilibrium, the concentrations of species:

A. Increase B. Decrease C. Stay constant D. Fluctuate

17. Which does not affect equilibrium position?

A. Temperature B. Pressure C. Catalyst D. Concentration

18. A catalyst affects equilibrium by:

A. Increasing yield

B. Shifting position

C. Increasing rate equally in both directions

D. Changing the equilibrium constant

19. What does measure?

A. Reaction rate

B. Product:reactant ratio at equilibrium

C. Heat of reaction

D. Pressure

20. For:
Increasing pressure causes equilibrium to shift:

A. Right B. Left C. No change D. Decompose catalyst

21. If the forward reaction is exothermic, increasing temperature will:

A. Increase product yield

B. Shift equilibrium right

C. Shift equilibrium left

D. No effect

22. Decreasing product concentration shifts equilibrium:

A. Left B. Right C. No effect D. Slows reaction

23. Dynamic equilibrium means:

A. Reaction has stopped

B. Forward rate is higher

C. Equal rates of forward and reverse reactions

D. Product equals reactant in amount

24. If , then:

A. More reactants

B. More products

C. Equal quantities

D. No reaction occurs
25. is only affected by:

A. Concentration B. Temperature

C. Pressure D. Catalyst

26. At equilibrium, adding a catalyst will:

A. Increase product yield

B. Change

C. Reach equilibrium faster

D. Shift equilibrium

27. Which system is most affected by pressure change?

A. Solid + liquid

B. Gases with same number of moles

C. Gases with unequal moles

D. Aqueous solution

28. For the reaction:

What happens if pressure is decreased?

A. Shifts left B. Shifts right

C. No effect D. Rate increases

A. Reaction has stopped

B. Reactants predominate

C. Products dominate

D. Reaction is fast

30. If a reaction has reached equilibrium and you increase temperature

A. Shift right

B. Shift left

C. No effect

D. Decrease yield

🔹 Question 1: Atomic Structure (20 marks)

(a) Define the following terms:

(i) Isotopes (1)

(ii) First ionisation energy (2)

(iii) Relative atomic mass (2)

[5 marks]

(b) The element magnesium has three isotopes:

: 10.0%

: 11.0%

Calculate the relative atomic mass of magnesium.

[3 marks]

© Explain the trend in first ionisation energy across Period 3 from sodium to
argon.

[4 marks]

(d)

(i) Write the full electron configuration of a sulfur atom.

(ii) How many unpaired electrons does sulfur have?

(iii) Explain why the first ionisation energy of sulfur is lower than that of
phosphorus.

[5 marks]
€ Describe the principle of a time-of-flight (TOF) mass spectrometer,
outlining how it can be used to determine the relative atomic mass of an
element.

[3 marks]

🔹 Question 2: Ionisation Energies and Sub-Shells (10 marks)

(a) The table below shows successive ionisation energies of an element:

Ionisation number 1st 2nd 3rd 4th 5th 6th 7th 8th 9th

Ionisation energy (kJ/mol) 578 1820 2740 11600 14800

(i) What is the group number of this element?

[3 marks]

(b)Explain why the second ionisation energy of sodium is significantly

[3 marks]
© Describe how shielding and nuclear charge affect ionisation energies.

[4 marks]

🔹 Question 3: Chemical Equilibria Principles (20 marks)

(a) Define the following terms:

(i) Reversible reaction

(ii) Dynamic equilibrium

[2 marks]

(c) For the reaction:

(i) Write the expression for .

Pressure is increased

Temperature is increased

A catalyst is added
[6 marks]

© A reaction mixture at equilibrium has the following concentrations:

Mol dm⁻³

Mol dm⁻³

Mol dm⁻³

Calculate the value of .

[4 marks]

(d)What does it mean if ?

Explain how the value of indicates the position of equilibrium.

[3 marks]

€ State two conditions required for a system to reach dynamic equilibrium.

[2 marks]
 (e) Explain why catalysts do not affect the value of .

[3 marks]

🔹 Question 4: Le Chatelier’s Principle Applications (20 marks)

(a) The equilibrium below is established in a closed container:

(i) State what happens to the equilibrium position if:

Pressure is increased

Temperature is decreased

C is continuously removed

Give reasons in each case.

[6 marks]
 (b)Explain the economic compromise in the Haber Process
regarding temperature and pressure.

[4 marks]

© The following equilibrium is studied:

The forward reaction is exothermic.

Predict and explain what happens to the value of when temperature is

[3 marks]

(c) Outline how equilibrium yield and rate can be optimised

[4 marks]

€ Give one example of a homogeneous and one heterogeneous equilibrium.

[3 marks]