BlogChemistryQCE Practice Questions for Unit 3 & 4 Chemistry External Assessment

QCE Practice Questions for Unit 3 & 4 Chemistry External Assessment

It can be hard to find good practice questions to help you prepare for your QCE Chemistry External Assessment (EA). To study well, you’ll obviously want practice questions with answers to refer back to, so you know where to improve!

Lucky for you, we’ve got exactly that. Once you’ve had a go at all 25 Chemistry EA practice questions, you’ll be able to download the solutions.

Keen to begin studying? Let’s go!

Chemistry EA Practice Questions

Question 1 (1 mark)

Explain what it means for a state of dynamic equilibrium to have been reached in a reversible reaction.

Question 2 (3 marks)

The diagram below is an electrochemical cell. Label the following on the diagram:

Chemistry EA Practice Questions - Q2

(a) The positive electrode (cathode) and the negative electrode (anode)

(b) The direction of the flow of electrons 

(c) The direction of the movement of the ions in the salt bridge

Question 3 (3 marks)

Shown below are two amines. Determine which structure contains a secondary carbon and which structure contains a tertiary carbon. Justify your answer.

Image sourced from Master Organic Chemistry

Question 4 (2 marks)

Calculate the concentration of hydroxide ions (OH) at pH 10.5. Show your working.

Question 5 (2 marks)

Calculate the concentration of hydrogen ions (H+) at pH 2.7. Show your working.

Question 6 (3 marks)

If 10.25 mL of a 0.8 M standardised solution of sodium hydroxide (NaOH) is required to neutralise 9.00 mL of sulphuric acid (H2SO4), calculate the concentration of the sulphuric acid solution (in mol/L). Show your working. 

Question 7 (4 marks)

On the axes below, sketch the titration curve when 0.2 M hydrochloric acid (HCL) is titrated with 0.2 M sodium hydroxide (NaOH) and label the:

(a) initial pH of the acid 

(b) equivalence point 

(c) half-equivalence point

(d) buffer region

Chemistry EA Practice Questions - Q7

Image sourced from QCAA Chemistry Public Use Practice Paper

Question 8 (2 marks)

Calculate the percentage yield (by mass) for hydrogen in the following reaction:

Mg(s) + H2SO4(aq) → H2(g) + MgSO4(aq)

Question 9 (2 marks)

If Kc is larger than 10-3 is there significantly more reactant or product species present at the equilibrium? Explain your answer with reference to the Kc formula. 

Question 10 (3 marks)

Explain how soap is able to remove grease. Refer to intermolecular forces in your answer.

Question 11 (2 marks)

Determine the name of the polypeptide chain below (using the amino acid abbreviations).

Chemistry EA Practice Questions - Q11

Question 12 (2 marks)

Explain the relationship between the strength of an acid and electrical conductivity.

Question 13 (1 mark)

What types of electrochemical cells use energy from an external source?

Question 14 (4 marks)

Distinguish between galvanic and electrochemical cells.

Question 15 (2 marks)

What is the definition of a strong acid in terms of its Ka? Give an example of a strong acid.

Question 16 (2 marks)

What is the definition of a strong base in terms of its Kb? Give an example of a strong base.

Question 17 (3 marks)

Distinguish between strong acids/bases and weak acids/bases.

Question 18 (2 marks)

Define the cell potential and provide the formula associated with it.

Question 19 (2 marks)

Explain the relationship between pH and hydrogen ion concentration [H+].

Question 20 (4 marks)

Sodium carbonate (Na2CO3) is a relatively strong base with a pH of approximately 11-12. Hydrochloric acid (HCl) is a strong acid with a pH of approximately 1-2. The neutralisation reaction of hydrochloric acid and sodium carbonate occurs according to equation (1):

Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq)+ H2O(l) + CO2(g)

However, as the carbonate ion in sodium carbonate can accept two H+ ions in an acid-base reaction, the reaction occurs in two successive steps. The first step is given below.

Na2CO3(aq) + HCl(aq)NaHCO3(aq) + NaCl(aq)

(a) Determine what the second step will be.

(b) Deduce what this means in terms of the number of equivalence points.

Question 21 (3 marks)

Differentiate between random and systematic error and give an example for each that could occur during a titration reaction.

Question 22 (2 marks)

Apply IUPAC rules to name the following structures:

(a) Chemistry EA Practice Questions - Q22

Image sourced from Oxford Chemistry Units 3 & 4


Chemistry EA Practice Questions - Q22b

Image sourced from Oxford Chemistry Units 3 & 4

Question 23 (4 marks)

For each of the following reactions, determine what kind of organic reaction has occurred (be specific).


Image sourced from Oxford Chemistry Units 3 & 4


Image sourced from Oxford Chemistry Units 3 & 4


Image sourced from Oxford Chemistry Units 3 & 4


Image sourced from Oxford Chemistry Units 3 & 4

Question 24 (4 marks)

Explain how glucose monomers combine to form a branched glycogen polymer.

Question 25 (4 marks)

Identify the organic compound from the mass spectrum below.  

Solutions to Chemistry EA Practice Questions

Click here to download the solutions to the 25 practice questions above!

On the hunt for other QCE Chemistry resources?

We’ve got plenty more practice questions for you to use to revise previous content from throughout the year! Check them out:

You’ll also want to have a look at our nifty guides for working on your QCE Chemistry assessments below:

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