Take a practice exam under real conditions
This site’s practice exam has the same structure as the real one: 60 multiple-choice questions in 90 minutes and 7 FRQs in 105 minutes. Keep conditions as close to the real thing as you can:
- One sitting: a break of only about 10 minutes between sections, with no phone and no looking things up.
- Strict timing: stop when time is up, and pace yourself as in 4.1.3.
- The same tools as the exam: a calculator, the official equation sheet and periodic table, and no other notes.
- Handwrite the FRQs: real FRQs are handwritten, so write yours on paper, then score them against the scoring points.
Review: find the cause of every miss
| Cause | Fix |
|---|---|
| Knowledge gap | Relearn it in the lesson, then practice |
| Misreading | Circle what’s asked; recheck after answering |
| Calculation slip | Show steps and units; check the magnitude |
| Out of time | Practice pacing; do sure questions first |
Diagnosis: fix the units that cost the most points first
The unit with the lowest score isn’t always the one to fix first. Unit 3 is worth 18–22%, so at the same score it loses far more points than a 7–9% unit. Rank units by loss index = (1 − fraction correct) × unit weight and start with the largest.
Question counts follow the unit distribution of this site’s practice exam (60 multiple-choice questions). Sample data is filled in; replace it with your own results.
Example 1: estimating an AP score
On a practice exam, a student gets 41 multiple-choice questions right and 27 FRQ points (out of 46). Using composite = MCQ × 50/60 + FRQ × 50/46, about what AP score is that? (From the 2018 practice exam: 5 for 75 or more, 4 for 60–74, 3 for 44–59.)
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Multiple-choice part.
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FRQ part.
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Composite. 34.2 + 29.3 = 63.5, between 60 and 74, so about an AP 4.
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Distance to a 5. About 11.5 points short, equal to roughly 14 more multiple-choice questions or about 11 more FRQ points; gaining some in each section is more realistic.
Example 2: which unit to fix first
On the same exam, the student got 9 of 13 Unit 3 questions and 2 of 5 Unit 5 questions right. Unit 5 has the lower score; should it come first? (Use the midpoints of the CED weight ranges: Unit 3 20%, Unit 5 8%.)
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Loss index for Unit 3.
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Loss index for Unit 5.
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Conclusion. Unit 3 has the larger index, so fix Unit 3 first: it carries more points on the exam, so bringing it up recovers more. Unit 5 comes next.
- Didn’t know how to convert between Ksp and solubility
Go back to U7.11.
- The question asked for pOH and the answer gave pH
Recheck what was asked after answering.
- Calculated 0.693 ÷ 0.0050 as 13.9
The right answer is 139; a magnitude check catches it.
- Only part (a) of the last FRQ was written before time ran out
Budget time by points and skip past anything you’re stuck on.
- Couldn’t remember whether a catalyst affects K
The fact wasn’t learned firmly.
- The question gave 273 K but 298 K was substituted
The given conditions weren’t used.
- mL wasn’t converted to L, so the result was 1000 times too large
Writing units in every substitution prevents this.
- The first 40 multiple-choice questions took 75 minutes, leaving only guesses for the last 20
Multiple choice averages about 1.5 minutes per question; check your progress at set points.
Common mistakes
Mistake 1: “Only the total score of a practice exam matters.” The total tells you where you are; the causes of your misses and how they spread across units tell you what to do next.
Mistake 2: “Fix whichever unit has the lowest score first.” Multiply by the unit’s weight too. A heavily weighted unit, even if its score isn’t the lowest, recovers more points when you bring it up.
Mistake 3: “In the last few weeks, just do a new practice exam every day.” Without reviewing, the same mistakes keep coming back. One or two full exams a week, with the rest of the time spent reviewing and fixing weak units, works better.
Quick check
Which is closest to real exam conditions?
Only a score under real conditions reflects how you’ll do on the exam.
How many questions and how much time are in the multiple-choice section?
The 7 FRQs take 105 minutes.
With 48 multiple-choice questions right and 30 FRQ points, the composite is about:
48 × 50/60 + 30 × 50/46 = 40.0 + 32.6 = 72.6.
What is the most important step when reviewing a practice exam?
Different causes need different fixes.
With three weeks left before the exam, which plan makes most sense?
Practice exams expose problems; review and targeted study fix them.
Unit 8 (weight 13%) is at 50% correct and Unit 2 (weight 8%) at 40%. By loss index, which comes first?
Unit 8: 0.50 × 13 = 6.5; Unit 2: 0.60 × 8 = 4.8.
AP-style practice
This is a 4-point short question; give yourself 9 minutes on the timer.
A 0.150 M solution of a weak monoprotic acid HA has a pH of 2.85.
(a) Calculate Ka for HA.
(b) Calculate the percent ionization of HA.
(c) If the solution is diluted to 10 times its volume, does the percent ionization of HA increase, decrease or stay the same? Explain using Q and K.
(d) 50.0 mL of this HA solution is mixed with 25.0 mL of 0.150 M NaOH. Find the pH of the mixture.
Model answer and scoring
(a) [H⁺] = [A⁻] = 10^−2.85 = 1.41 × 10⁻³ M; Ka = (1.41 × 10⁻³)² ÷ (0.150 − 0.00141) = 1.34 × 10⁻⁵.
(b) Percent ionization = 1.41 × 10⁻³ ÷ 0.150 × 100% = 0.94%.
(c) It increases. Right after dilution every concentration is 1/10 of before, so Q = [H⁺][A⁻]/[HA] becomes 1/10 of Ka; Q < Ka, so the equilibrium shifts toward ionization and a larger fraction ionizes.
(d) n(HA) = 7.50 × 10⁻³ mol and n(OH⁻) = 3.75 × 10⁻³ mol, so half the HA reacts and [HA] = [A⁻]; pH = pKa = −log(1.34 × 10⁻⁵) = 4.87.
Scoring (4 points): (a) Ka; (b) percent ionization; (c) increases, explained with Q < K; (d) half-neutralized, so pH = pKa.
Summary
- A full practice exam: one sitting, strict timing, only a calculator and the official equation sheet, with handwritten FRQs scored against the scoring points.
- Review: sort every miss into knowledge gap, misreading, calculation slip or out of time, and fix each accordingly.
- Diagnosis: loss index = (1 − fraction correct) × unit weight, so fix the largest first; in the last weeks, take one or two practice exams a week and spend the rest of the time reviewing and filling gaps.
AP tip: Schedule your last full practice exam about a week before the real one, leaving time to review it; in the last day or two, skip new exams and reread your misses and your own mistakes checklist.
Sources: exam structure and unit weights from the College Board AP Chemistry Course and Exam Description; the score conversion follows the 2018 released practice exam and is only a rough guide.