FRQs 4-6 – Short Answer Questions

Overview

The AP Chem SAQs are the four short free-response questions on Section II of the AP Chemistry exam, each worth 4 points. You'll answer them alongside three long FRQs (10 points each) in the 105-minute free-response section, which counts for 50% of your exam score. Together, the four short questions are worth 16 of the 46 free-response points, roughly a third of Section II.

Unlike the long FRQs, each short question stays focused on one topic. You might get a photoelectron spectroscopy graph, a Lewis structure and geometry sequence, a lab data calculation, or a targeted equilibrium problem. Think of them as sprints rather than marathons. Get in, show specific knowledge precisely, and move on. A calculator is allowed on both sections, and you get the periodic table and equation sheet for the whole exam.

The good news: short FRQs are predictable. Once you recognize the question type, you basically know what's coming. That predictability is your biggest advantage, and this guide shows you how to use it. (For the 10-point integrated questions, see the long FRQ guide.)

How AP Chem Short FRQs Are Scored

Each short FRQ is worth 4 points, and each point is tied to one specific element of your answer. There's no sliding scale within a point. You either give the complete, correct response that the scoring guideline describes, or you don't earn it. Parts are scored independently, though, so a wrong answer in part (a) doesn't automatically sink parts (b) through (d).

Here's how the four most common point types typically work in practice:

Pay attention to the task verbs, because they tell you exactly how much to write. The exam uses a defined set:

• Calculate means show the math: expression, substituted numbers, answer with units and sig figs.
• Identify or Indicate means a short, direct answer. One word or phrase can earn the point.
• Explain means say how or why, using evidence and reasoning, not just what.
• Justify means provide evidence that supports the claim and connect it to the claim.
• Predict means state the cause or effect of a change in the system.
• Represent/Draw means use the correct diagram, graph, or symbols.

Matching your answer length to the verb is the fastest scoring upgrade most students can make. "Identify" with three sentences wastes time. "Justify" with three words loses the point.

How to Answer AP Chem SAQs, Step by Step

Budget roughly 7 minutes per short FRQ. Section II gives you 105 minutes for 7 questions, and the long questions need more than their equal share, so finishing a short question in 5 minutes banks time for the harder stuff. Here's a repeatable process.

Step 1: Read all parts first (30-60 seconds)

Before writing anything, skim parts (a) through (d). Later parts often hint at earlier answers. If part (c) says "using your answer from part (b)," those parts are linked and you need to do them in order. Reading ahead also tells you the question type, which tells you the playbook.

Step 2: Identify the question type (within the first 30 seconds)

Within half a minute you should be able to name the pattern: "this is a PES question" or "this is Lewis structure plus VSEPR." Each type follows a predictable script:

• A photoelectron spectroscopy question asks you to interpret peaks, explain binding energies with Coulomb's law, and predict spectra for related elements.
• A molecular structure question has you draw a Lewis structure, determine geometry, then explain a property.
• A lab scenario involves processing data, doing a calculation, then reasoning about results.

Recognizing the type converts anxiety into a checklist.

Step 3: Execute systematically, part by part

Run the standard procedure for the type. For example, for molecular structure:

1. Count valence electrons
2. Draw the Lewis structure
3. Count electron domains around the central atom
4. Determine geometry from VSEPR
5. Assess polarity from geometry and bond polarities

For lab calculations:

1. Identify what you're solving for
2. List given values with units
3. Select the formula (it's probably on your equation sheet)
4. Calculate, watching sig figs
5. Sanity-check the answer

Units are your built-in error detector. Carry them through every step. If you're calculating molarity and the units don't simplify to mol/L, something's wrong.

Step 4: Spend time proportionally and don't get stuck

Four parts worth 1 point each deserve roughly equal time. Don't perfect part (a) for 4 minutes and leave 3 minutes for everything else. If a calculation fights back, write your setup, give a reasonable estimate, and move on. Earning 3 of 4 points beats running out of time chasing the fourth.

Step 5: Be precise, not verbose

With only 1 point per part, you can't earn extra credit for elaboration, but you can lose the point for an incomplete core idea. A strong short-FRQ explanation looks like this (editorial example): "HF has hydrogen bonding because F is small and highly electronegative; HCl has only dipole-dipole forces. Hydrogen bonding is stronger, so HF has the higher boiling point." Direct, complete, done.

Worked Example: A Real Short FRQ

This is an actual sample short FRQ from the College Board, with how each point was awarded. The question gives the complete photoelectron spectrum of an unknown element.

(a) Draw an X above the peak that corresponds to the orbital with electrons that are, on average, closest to the nucleus. Justify your answer in terms of Coulomb's law. (1 point)

The point goes to placing the X above the leftmost peak (highest binding energy) with the justification that electrons closest to the nucleus have the greatest binding energy because the attraction between charges is strongest when the distance r between them is smallest. Notice the structure: the answer plus the Coulomb's law reasoning. The X alone doesn't earn it.

(b) Based on the spectrum, write the complete electron configuration of the element. (1 point)

One point for the correct configuration: $1s^{2}2s^{2}2p^{6}3s^{1}$ (the element is sodium). You read this off the spectrum by matching peaks to subshells and peak heights to electron counts.

(c) On the graph, draw the peak(s) corresponding to the valence electrons of the element with one more proton in its nucleus. (2 points)

That element is magnesium ($3s^{2}$). One point for placing the new peak just to the left of the rightmost peak (more protons means higher binding energy for the 3s electrons). A second point for drawing it at twice the height of the rightmost peak (two electrons instead of one).

Total: 4 points. Every point maps to one specific, checkable element of the response. That's the entire game with short FRQs.

Common Short FRQ Types

Knowing the standard question types lets you prep a targeted playbook for each.

Photoelectron spectroscopy (PES). Expect to identify an element from its spectrum, explain relative binding energies using Coulomb's law and shielding, and predict how the spectrum changes for a related element. Core facts: electrons closer to the nucleus have higher binding energy, more protons mean stronger attraction, and peak height reflects the number of electrons in that subshell. Within a shell, s peaks sit left of p peaks.

Molecular structure and properties. The usual progression: draw the Lewis structure, identify the geometry and bond angle, then explain a property difference. Know the core angles cold: linear 180°, trigonal planar 120°, tetrahedral 109.5°, trigonal bipyramidal 90°/120°, octahedral 90°. Lone pairs compress angles slightly below these ideal values. And keep molecular geometry separate from electron geometry. NH3 has 4 electron domains (tetrahedral electron geometry) but only 3 bonds, so its molecular geometry is trigonal pyramidal.

Laboratory data analysis. Concentration from absorbance, percent composition from masses, rate constants from kinetics data, K from equilibrium concentrations. These reward extreme care: using the wrong data row, forgetting mL-to-L conversions, or using 16 g/mol for water instead of 18 g/mol all cost the point.

Focused equilibrium problems. Calculate K from concentrations, compare Q to K and predict the shift direction, or explain a Le Chatelier shift for a specific stress. The classic trap: solids and pure liquids never appear in equilibrium expressions. For CaCO3(s) ⇌ CaO(s) + CO2(g), K = [CO2] only.

Buffers and acids/bases. Acids and bases carry 11-15% of the multiple-choice weighting and show up regularly in FRQs too. The Henderson-Hasselbalch equation, pH = pKa + log([A⁻]/[HA]), does most of the work. When the acid and base concentrations are equal, pH = pKa. Adding strong acid converts A⁻ to HA; adding strong base converts HA to A⁻.

Common Mistakes

• Restating the question instead of explaining. "Ice floats because it's less dense" earns nothing if the question asks why. Give the chemistry: hydrogen bonds in ice form an open hexagonal structure with more space between molecules than in liquid water.
• Comparing only one substance. "NaCl has ionic bonding" is half an answer. Comparison points require both substances, the direction of the difference, and the reason: "NaCl has strong ionic bonds while CH4 has only weak London dispersion forces, so NaCl has a much higher melting point."
• Sloppy Lewis structures. One extra or missing electron costs the whole point. Count valence electrons first, then double-check the total in your final drawing, including lone pairs.
• Dropping units mid-calculation. Units catch errors before the grader does. Carry them through every line and confirm the final units match what you're solving for.
• Including solids or liquids in K expressions. Only gases and aqueous species appear. This single habit error shows up constantly on equilibrium parts.
• Time hoarding on one part. Each part is usually worth 1 point, so each deserves roughly equal time. If you're stuck, write your setup and a reasonable estimate, then move on. Three earned points beat one perfect part.

Practice and Next Steps

The short FRQs reward repetition until the patterns become automatic. When a PES spectrum appears, you should immediately start counting peaks; when a Lewis structure is requested, your hand should already be tallying valence electrons. Build that automaticity with FRQ practice with instant scoring, which tells you exactly which points you earned and why, and browse the full FRQ question bank to drill specific question types like PES or equilibrium. Working through past AP Chem exam questions shows you exactly how the College Board phrases task verbs and awards points.

When you're ready to test pacing across the whole section, take a full-length AP Chem practice exam under timed conditions, then plug your results into the AP Chem score calculator to see where you stand. And since Section II is only half the exam, make sure you've also read the AP Chem MCQ guide for the other 50%.