QCAA Chemistry Exam Practice Questions for Unit 3 & 4

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

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

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 K_a? Give an example of a strong acid.

Question 16 (2 marks)

What is the definition of a strong base in terms of its K_b? 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):

Na₂CO_3(aq) + 2HCl_(aq) → 2NaCl_(aq)+ H₂O_(l) + CO_2(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.

Na₂CO_3(aq) + HCl_(aq)→ NaHCO_3(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)

Image sourced from Oxford Chemistry Units 3 & 4

(b)

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).

(a)

Image sourced from Oxford Chemistry Units 3 & 4

(b)

Image sourced from Oxford Chemistry Units 3 & 4

(c)

Image sourced from Oxford Chemistry Units 3 & 4

(d)

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!