The Most Common Chemistry Exam Mistakes (and How to Avoid Them)

Whether you’re sitting a QCE, VCE, HSC or IB Chemistry exam, the same mistakes come up year after year — and they’re almost always avoidable. This guide breaks down the seven most common errors students make in chemistry exams and shows you exactly how to steer clear of them, so you can pick up the marks you deserve. Let’s break them down (just like a decomposition reaction — yes, we went there).

1. How to handle significant figures in chemistry exams

Chemistry examiners are particular about significant figures, and for good reason. If the question specifies a certain number of sig figs and you ignore it, those marks are gone. It sounds minor, but across a full exam paper, sloppy rounding can cost you five or more marks — enough to shift a grade boundary.

How to avoid it:

• Always check how many significant figures are in the data given.
• If the question says “correct to three significant figures,” don’t suddenly decide that four looks prettier.
• When in doubt, follow the least number of sig figs in the given data (unless it’s a multi-step calculation—then use more and round at the end).

2. Don't forget state symbols in chemical equations

You might think, “Do I really need to write (s), (l), (g), or (aq)?” Yes. You do. Those tiny letters can make the difference between full marks and a deduction. In past QCE exams, students who forgot state symbols in precipitation reactions lost an easy two marks. Don’t be that student.

How to avoid it:

• Memorise your common state symbols.
• If you're dealing with an acid-base reaction in water, assume everything is aqueous unless told otherwise.
• Gases (like H₂ and CO₂) are (g), solids (like precipitates) are (s), and water is always (l).

💡 Case Study: In a past QCE exam, students who forgot state symbols in a precipitation reaction lost an easy two marks. Don’t be that student.

3. Always show full working in chemistry calculations

Even if you arrive at the correct answer, if you don’t show your steps, the examiner will assume you guessed. In most chemistry exams, the method marks are worth more than the final answer — so showing your working is where the points are.

How to avoid it:

• Always include formulae before plugging in numbers.
• Use units at every step.
• Box or highlight your final answer so it doesn’t get lost in a sea of scribbles.

4. Common mistakes in acid-base and redox reactions

Half-equations and balancing reactions can be a nightmare if you don’t practise. One wrong coefficient, and suddenly water is breaking the laws of chemistry. Redox questions appear in every curriculum — QCE, VCE, HSC and IB — and they’re consistently among the worst-answered questions on examiner reports.

How to avoid it:

• Use the OIL RIG method for redox reactions (Oxidation Is Loss, Reduction Is Gain of electrons).
• Practise writing half-equations—seriously, do at least 10 before the exam.
• If dealing with acidic conditions, remember to balance oxygens with H₂O and hydrogens with H⁺.

💡 Tip: Think of oxidation as a fire (burning gives off oxygen), and reduction as rescue (gaining electrons like a life-saving recharge!).

5. Ready the question carefully: command terms matter

You speed-read a question, think “Easy!” and start writing. Five minutes later you realise you answered something completely different. This is one of the most common reasons students lose marks across all exam subjects, not just chemistry.

How to avoid it:

• Underline or highlight key terms (e.g., explain, justify, calculate, describe).
• If it’s a multi-part question, make sure you address all parts.
• Don’t assume—read twice before answering.

6. Time management in chemistry exams

Leaving a five-mark extended response until the last two minutes of the exam? Bold strategy. Doesn’t usually pay off.

How to avoid it:

• Allocate time per question based on marks. A 10-mark question? Spend at least 10–12 minutes on it.
• If you get stuck, move on and come back later.
• Keep an eye on the clock—don’t get lost in a single question.

7. Practise past chemistry exam papers

If you’re not doing past exams, you’re trying to learn to swim by reading about it. It won’t end well. Past papers show you the style of questions, the depth examiners expect, and the marking schemes they use. There is no better revision tool.

How to avoid it:

• Do as many QCE past papers as possible.
• Time yourself under exam conditions.
• Analyse marking schemes to see what examiners expect.

You can access past exam papers from your curriculum authority:

• QCE: QCAA past papers
• VCE: VCAA past exams
• HSC: NESA past papers

💡 Case Study: Students who practised at least five past exams scored, on average, 15% higher than those who didn’t. Let that sink in.

Final Thoughts

Chemistry is tough—but so are you. By avoiding these common mistakes, you’ll be setting yourself up for top marks. Practise consistently, revise smartly, and remember: chemistry is just like baking, but with more explosions (and fewer edible results). You’ve got this. Now go smash that exam!

Need Help Avoiding These Mistakes?

Learnmate’s research shows that 70% of students achieving ATARs of 99+ engage one or more tutors. A Chemistry tutor can help you identify the mistakes you don’t even know you’re making — and fix them before exam day. Research from Evidence for Learning confirms that one-to-one tuition adds the equivalent of five additional months of academic progress.

You can find a tutor on Learnmate to help you refine your Chemistry skills, boost your confidence, and receive expert exam guidance. Connect with an experienced QCE Chemistry tutor on Learnmate and take your understanding to the next level!