Chemistry is about 45 of the 180 questions on the MDCAT. That is a quarter of the paper, and second only to Biology. It is also the subject where students lose marks they could have kept, because they spread their revision evenly across a syllabus the exam does not treat evenly.
The official topic list is set by PMDC and you can see it subject by subject on the syllabus page. What follows is how to work through it, not a replacement for it.
Three chemistries, one paper
FSc Chemistry breaks into three parts, and they behave differently in an MCQ exam.
Physical chemistry is where the numericals live: the mole concept, gas laws, thermochemistry, equilibrium, reaction kinetics, electrochemistry. These are the most learnable marks in the subject, because the same handful of calculations come up in slightly different clothes every year. Once a calculation is automatic, it is a mark you will not lose on a bad day.
Organic chemistry looks like the biggest memory load and is actually the most pattern-based. You are not being asked to invent a synthesis. You are being asked to recognise a functional group, know what reacts with it, and know what comes out.
Inorganic chemistry is the most straightforward recall: periodic trends, the s and p block, transition elements. Easy to learn, easy to forget, so it needs revisiting rather than understanding.
The numericals worth drilling until they are automatic
Do these until you can finish one in under a minute without writing much down:
- Mole concept and stoichiometry. Moles, molarity, limiting reagent, percentage yield. Everything else in physical chemistry stands on this.
- Gas laws. The ideal gas equation, and knowing which quantity is being held constant before you pick a formula.
- Thermochemistry. Enthalpy changes, Hess's law, the sign conventions. The sign is where most marks go missing.
- Equilibrium. Writing the expression for Kc correctly, and Le Chatelier's principle applied to a change in pressure, temperature or concentration.
- Reaction kinetics. Order of reaction, rate from a given data table, and what a catalyst does and does not change.
- Electrochemistry. Oxidation numbers, balancing redox, and reading a table of electrode potentials the right way round.
- pH and buffers. pH, pOH and the relationship between them, strong against weak.
Pay attention to units. A worrying number of chemistry marks are lost by students who did the chemistry correctly and the arithmetic in the wrong unit.
Organic chemistry: learn the groups, not the pages
Work functional group by functional group rather than chapter by chapter. For each one you want three things in your head: how to recognise it, what it reacts with, and what the product looks like.
- Hydrocarbons. Alkanes, alkenes and alkynes, and whether a reaction is substitution or addition.
- Alkyl halides. The substitution and elimination ideas, and what pushes a reaction one way rather than the other.
- Alcohols and phenols. Oxidation products, and how phenol behaves unlike an ordinary alcohol.
- Aldehydes and ketones. The tests that tell them apart are near-guaranteed marks.
- Carboxylic acids and their derivatives. Esterification, and acidity compared with alcohols.
- Macromolecules and biochemistry. Where the chemistry paper quietly overlaps with Biology.
Named reactions and distinguishing tests are worth a dedicated revision card. They are the definition of a cheap mark: small to learn, frequently asked.
Inorganic: trends beat lists
Do not memorise a table of properties element by element. Learn the trends across a period and down a group, in atomic radius, ionisation energy, electronegativity and metallic character, then reason your way to the answer. It is less to carry, and it survives questions you have not seen before.
How to practise it
Reading chemistry creates a strong and misleading feeling of understanding. The test is whether you can pick the right option in sixty seconds under pressure, so practise in that form from the start.
Work topic by topic in MDCAT Chemistry practice, read the explanation for every question you get wrong, and keep a short list of the mistakes you repeat. That list is almost always shorter than students expect, usually about ten recurring errors, and fixing those ten is worth more than another pass through the book.
When your accuracy on a topic holds, move on. When it does not, that topic is tomorrow's work.