A scientist is investigating the atomic structure and properties of Phosphorus (P) and Sulfur (S). The scientist obtains the photoelectron spectrum for Phosphorus, which is shown in Figure 1.
Figure 1. Photoelectron spectrum of Phosphorus (binding energy scale increases to the left)
A.
Based on the photoelectron spectrum in Figure 1, write the complete ground-state electron configuration for the Phosphorus atom.
B.
A student claims that the atomic radius of a Sulfur atom is smaller than that of a Phosphorus atom. Do you agree or disagree? Justify your answer using principles of atomic structure.
C.
The first ionization energy of Sulfur is 1000 kJ/mol, while the first ionization energy of Phosphorus is 1012 kJ/mol. Justify this observation based on electron configuration and Coulombic attraction.
Table 1. Isotopic data for naturally occurring Sulfur
Isotope
Atomic Mass (amu)
Relative Abundance (%)
S-32
31.97
95.02
S-33
32.97
0.75
S-34
33.97
4.23
D.
Using the data in Table 1, calculate the average atomic mass of Sulfur. Show your work. The scientist analyzes a sample of naturally occurring Sulfur and records the data shown in Table 1.
What the FRQ 5 Short Answer asks
FRQ 5 is the second of four short-answer questions on the AP Chemistry exam, worth 4 points and focused on one topic. In this set, you write or predict, evaluate a student’s claim, justify a result, and finish with a calculation.
An electron configuration, net ionic equation, or geometry
1 pt
B
Part B: Evaluate a claim
Agree or disagree with a student’s claim, with a reason
1 pt
C
Part C: Justify
The chemical reason behind an observation or comparison
1 pt
D
Part D: Calculate
A calculation from the data, with units
1 pt
How FRQ 5 Short Answer practice works
Each question follows the exam’s format, from the full prompt to a score on every part.
1
Read the full question
The setup, the figure or data table, and every part, laid out the way the exam shows them.
2
Write on a 9-minute timer
A pace that fits all seven questions into the 105-minute section. Pause it or turn it off, and your response saves as you go.
3
Submit for a score out of 4
Your response is scored against the scoring guidelines written for that question. Your first score is included.
Feedback on every part
A summary at the top tells you what to work on next. Below it, each part shows whether you earned the point and what the scoring guidelines were looking for.
Earned the point. You correctly predicted that the sign of ΔH_soln is positive based on the endothermic nature of the reaction.
Part B: 0/1 point
Did not earn the point. While you agreed with the claim, your justification was incomplete. You discussed the energy needed to break the lattice structure but failed to compare it to the energy released during hydration. A valid justification must address the net balance between these two energy terms (lattice energy > hydration energy) to explain why the overall process is endothermic.
Detailed feedback on a practice FRQ 5 Short Answer
Questions about the FRQ 5 Short Answer
How many responses can I get scored?
You can read every question without a plan. Your first scored response is included. A plan unlocks unlimited scoring.
How do I answer the agree or disagree part?
State whether you agree, then give the chemical reason. An answer with no reasoning does not earn the point.
How much should I write for each part?
Match the task verb. Identify can take a word or phrase. Explain and justify need the chemical reason, stated in a sentence or two.
How are short-answer questions different from FRQs 1 to 3?
Short answers are 4 points and stay on one topic, usually with one point per scored step. FRQs 1 to 3 are 10-point problems with about six parts.
Can I use a calculator and the equations sheet?
Yes. The practice screen has a calculator and the AP Chemistry equations sheet with the periodic table, which you also get on exam day.
More AP Chemistry practice
FRQ 1 Long Answer practice
FRQ 1 long-answer questions with every part, figure, and data table.
