Overview
The single most important rule of IB Chemistry Paper 1 multiple choice fits in five words: never leave an answer blank. There is no negative marking, so a wrong answer costs you nothing beyond the mark you were never going to get — while a blank guarantees a zero. That one fact reframes the whole section: every question is worth attempting, every eliminated option improves your odds, and a considered guess always beats an empty box. This is a technique-first walkthrough of how to turn that advantage, plus a handful of habits, into a higher Paper 1 score.
What Paper 1 multiple choice is
For the IB Diploma Programme, on the 2025 syllabus, Paper 1 opens with a multiple-choice section — Paper 1A — sat with no notes allowed. Each question gives a stem and four options, of which exactly one is correct. The count is typically around 30 questions at SL and 40 at HL, though you should always confirm the current figures on your subject page, since the exact number, the time allowed, and which materials (periodic table, data booklet) are supplied can be updated.
The defining feature is the marking: there is no negative marking. A correct answer scores one mark; a wrong answer scores zero. You are never penalised for guessing. Hold that thought — it drives almost everything that follows.
Why you should answer every question
For the IB Diploma Programme, because a wrong answer and a blank both score zero, leaving a question empty can only ever *lose* you marks relative to guessing. A blind guess between four options is a 25% chance of a mark for free; once you have cut one or two options, that climbs to a one-in-three or a coin-flip on a mark you would otherwise have thrown away.
So the rule is absolute: before the section ends, every question must have an answer. If you are short on time, spend the final minute filling in any remaining blanks rather than perfecting one hard question — a rushed guess on five unanswered questions will, on average, hand you marks that a tidy blank never will.
Reading the question — qualifiers and traps
For the IB Diploma Programme, most avoidable Paper 1 errors are reading errors, not chemistry errors. The examiners write stems precisely, and a single qualifier can flip the correct answer. Slow down for a heartbeat and underline the words that control the question:
- Negatives: "Which is NOT…", "EXCEPT", "which does not occur". Here you are hunting for the odd one out — the three that do fit are the wrong answers.
- Superlatives and extremes: "LEAST", "MOST", "greatest", "smallest". More than one option may be true; you need the ranked extreme.
- Absolutes: "always", "never", "all". These are frequently the mark of a distractor, because chemistry has so many exceptions.
Read the stem twice if it contains any of these. A student who knows the chemistry perfectly but reads "NOT" as "is" picks the wrong box with full confidence — and there is no working for a marker to rescue.
Elimination strategy
For the IB Diploma Programme, you rarely need to *know* the answer outright; you need to be the last option standing. Work by removing what cannot be true:
- Cut the clearly wrong first. Options that break a definition, violate conservation of mass or charge, or contradict a periodic trend can go immediately.
- Look for two opposites. Often one of a contradictory pair is the answer, which focuses your reasoning.
- Watch for half-right options. A statement that is true in its first clause and false in its second is still wrong — read the whole option.
- Narrow, then guess. If you are down to two and cannot separate them, pick one and move on. You have already turned a 1-in-4 into a 1-in-2.
Elimination is what makes guessing educated. Every option you rule out is a measurable rise in your expected marks.
Calculation MCQs — unit and order-of-magnitude checks
For the IB Diploma Programme, a chunk of Paper 1 is short calculations — moles, concentrations, empirical formulae, energetics, pH. The wrong options here are not random: they are engineered to be exactly what you get if you make a common mistake. That is the trap and, once you know it, the tell.
- Order-of-magnitude sanity check. Before you trust a number, ask whether it is roughly the right size. A concentration of 500 mol dm⁻³ or a pH of 27 is a signal you slipped a power of ten somewhere.
- Unit check. Confirm the answer is in the units the question asked for. Distractors often sit in the wrong unit — grams where moles were wanted, J where kJ mol⁻¹ was wanted.
- Beware the factor-of-2 distractor. Forgetting to double for a diatomic, dropping or adding a mole ratio, or halving a concentration on dilution all produce an option that is there waiting for you. If your answer matches an option but so does exactly half or double it, re-check the step.
- Beware unit-conversion distractors. cm³ not converted to dm³, or a mass left in mg, produces a clean wrong answer that looks right.
The lesson: seeing your number in the option list is not confirmation you are correct. The most tempting wrong answer is designed to look exactly that convincing.
Timing and flag-and-return
For the IB Diploma Programme, with roughly 30–40 questions in the section, aim for about 1 to 1.5 minutes per question as a working average. Not every question deserves equal time:
- Answer the ones you know quickly and bank the marks.
- If a question stalls you for more than about ninety seconds, put down your best current guess, flag it, and move on. You never leave it blank — the flag just means "revisit if time allows."
- Do a deliberate sweep at the end for flagged questions and any accidental blanks.
Managing the clock this way protects the easy marks at the back of the paper that panic-slow candidates never reach.
How to revise for multiple choice
For the IB Diploma Programme, multiple choice rewards a specific kind of preparation, and it is not passive re-reading.
- Do timed sets. Practise in blocks under the clock so pacing and the flag-and-return habit become automatic, not something you improvise on the day.
- Use real question styles. Work from genuine past-paper multiple choice so you meet the actual phrasing, qualifier patterns, and distractor design the examiners use.
- Mine your wrong answers. For every one you miss, write down why — misread qualifier, unit slip, factor-of-2, or a genuine content gap — and drill that pattern. Learning from wrong answers is the fastest single improver.
Volume of timed, realistic practice with honest review beats any amount of highlighting.
Common mistakes
For the IB Diploma Programme, none of these are about knowing less chemistry. They are about discipline under the clock.
- Leaving blanks — the only guaranteed way to lose a markable question.
- Misreading a qualifier — sailing past "NOT", "EXCEPT", or "LEAST".
- Trusting a calculator number because it appears in the options, without an order-of-magnitude or unit check.
- Falling for the factor-of-2 or unit-conversion distractor.
- Over-investing in one hard question while easy marks at the back go unattempted.
- Changing a correct first instinct without a concrete reason to.
How MarkScheme helps
MarkScheme links each syllabus point to a lesson, flashcards, and targeted practice, so you can build the recall multiple choice demands and drill it under timed conditions. Refresh the underlying content in the free [IB Chemistry SL course](/ib/courses/chemistry-sl) or [HL course](/ib/courses/chemistry-hl), and on the written paper you can [get an answer marked](/mark) against IB-style criteria. Pair this with the [IB Chemistry Paper 2 guide](/blog/ib-chemistry-paper-2-guide), drill full papers using the [SL past papers](/blog/ib-chemistry-sl-past-papers-guide) guide, and see the whole grade strategy in [how to get a 7 in IB Chemistry](/blog/ib-chemistry-how-to-get-a-7). The [IB guides hub](/guides/ib) ties the revision path together.
Frequently asked questions
This section covers Frequently asked questions — what IB examiners reward most often in past papers and coursework.
Is there negative marking in IB Chemistry Paper 1?
No. A wrong answer scores zero — the same as a blank — and you are not penalised for guessing. This is precisely why you should answer every question rather than leave any empty.
Should I guess?
Yes, always. Because there is no penalty for a wrong answer, a guess can only help. A blind guess between four options is a 25% chance of a mark; after eliminating one or two options, your odds rise further. Never hand back a question by leaving it blank.
How many questions are on Paper 1 multiple choice?
Typically around 30 at SL and 40 at HL, each with four options, but confirm the current count, timing, and supplied materials on your subject page, since these details can change between syllabus updates.
Can I use the data booklet or a calculator in Paper 1?
No notes are allowed in the multiple-choice section. Which reference materials (such as the periodic table or data booklet) and equipment are available can vary, so check the current specification for your session rather than assuming.
What is the fastest way to improve my Paper 1 score?
Timed practice on real question styles, followed by honest review of every wrong answer to find the pattern — a misread qualifier, a unit slip, a factor-of-2 error, or a content gap — and then drilling that weakness.