Updated for the 2020 online exam!

2020

FREE PRACTICE TESTAP® CHEMISTRY

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AP® CHEMISTRY Free Practice Test

INFORMATION IN THE TABLE BELOW AND ON THE FOLLOWING PAGES MAY BE USEFUL IN ANSWERING THE QUESTIONS IN THIS SECTION OF THE EXAMINATION.

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AP® CHEMISTRY Free Practice Test

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AP® CHEMISTRY Free Practice Test

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AP® CHEMISTRY Free Practice Test

CHEMISTRYTime—45 minutes

2 Questions

YOU MAY USE YOUR CALCULATOR FOR THIS SECTION.

Directions: Question 1 is a long free-response question that requires about 25 minutes to answer and is worth 10 points. Question 2 is a short free-response question that requires about 15 minutes to answer and is worth 8 points.

Write your response in the space provided following each question. Examples and equations may be included in your responses where appropriate. For calculations, clearly show the method used and the steps involved in arriving at your answers. You must show your work to receive credit for your answer. Pay attention to significant figures.

1. There are three (3) possible structures for carbon dioxide (CO2). The structure on the left is the most stable structure.

O C O O C O O O C

(a) Explain why the structure on the left is the most favorable representation for the bonding of CO2. Justify your answer using formal charges.

The Lewis dot structures for the decomposition of carbon dioxide (CO2) into carbon monoxide (CO) and oxygen (O2) as shown below:

2CO2(g) → 2CO(g) + O2(g)

OO+→ OCCO O

(b) Using the bond energy table provided, calculate ∆Hrxn.

Bond Enthalpy kJ/mol Bond Enthalpy kJ/mol

C – O 350 O = O 498

C = O 741

C O 1080

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AP® CHEMISTRY Free Practice Test

(c) Given the equation: 2 Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) ∆H = -860kJ/mol

Substance ∆Hf (kJ/mol)

Al(s)0

Al2O3(s)−1680

Fe(s)0

Fe2O3(s)(?)

A student was asked to calculate the ∆Hf for Fe2O3(s). The student calculated ∆Hf of Fe2O3(s) to be +820 kJ/mol.

Was the student correct in their calculation? Justify your reasoning.

(d) At high temperatures, N2(g) and O2(g) will react to produce 2NO(g) as represented below:

N2(g) + O2(g) ⇌ 2NO(g)

(i) Write the Kp expression for the reverse reaction.

(ii) A student is provided a rigid, evacuated vessel and injects samples of N2(g) and O2(g) . The student carefully raises the temperature to 1000°C, where the initial partial pressure of N2(g) is 3.00 atm and partial pressure of O2(g) is 0.81 atm. Once the system reaches equilibrium, the partial pressure of NO(g) is 0.061 atm. Calculate the value of Kp of the reverse reaction.

(iii) The student decides to run the reaction at a constant temperature of 200°C in a rigid 25.0L container. If the O2(g) is initially present in the container at 0.81 atm, how many moles of O2(g) are in the container?

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AP® CHEMISTRY Free Practice Test

2. The elements in group VII (17) exhibit different states of matter when observed at room temperature. Chlorine (Cl2) is a pale green gas while iodine (I2) is a grey solid.

(a) Explain this observation in terms of the type and relative strength of the intermolecular forces in each substance at room temperature.

(b) Fluoropolymers are produced from alkenes in which one or more hydrogen atoms have been replaced by fluorine. Two of the important members of this polymer class are polytetrafluoroethylene (PTFE), also known as teflon, and polyvinyl fluoride (PVF). A sample of the structure of each is shown below:

PVF PTFE

C F

Hnn

Predict which substance PTFE or PVF, would have the higher melting point. Justify your answer.

(c) In a separate activity, a student was asked to react 100 ml of 0.40 M copper (II) sulfate, CuSO4 (aq), with 100 mL of 0.40 M sodium hydroxide (NaOH). Two students each drew a particulate beaker drawing of the overall reaction and the drawings are shown below.

Beakers before mixing:

+

OH−

NA+Cu 2+

Key

SO42−

Student A (completion of reaction)

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AP® CHEMISTRY Free Practice Test

Student B (completion of reaction)

(i) Which student’s drawing correctly represents the reaction, Student A or Student B? Justify your answer.

(ii) Write the net ionic for the reaction of copper (II) sulfate, CuSO4 (aq) with sodium hydroxide (NaOH).

(iii) Calculate the final concentration on Na+ at the end of the reaction.

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CHANGES TO THE 2020 EXAM FORMATAP® CHEMISTRY

ONLINE TESTINGThe test will be conducted at home, at the same time around the world, and can be taken on any device: PC, laptop, tablet, or smart phone. You can either type your responses, or handwrite them and photograph them with your phone. If at all possible, plan to take your exam on a computer instead of phone, as scrolling through the problems may become difficult. Remember, the device you open the test link with is the device you will be using to submit your answers. You will need to print the approved formula sheet and periodic table prior to beginning the exam. You can have your calculator as well.TEST DURATIONThere will one 25-minute question, followed by 5 minutes to upload. There will be 15 minutes for the second question, followed by 5 minutes to upload. You cannot go back to the first question after the upload period. The first question will count for 60% of your total exam score, while the second question will count for 40% of your total exam score.QUESTION TYPEBoth questions will require students to explain chemical phenomena using models, theories, and representations at the particulate and macroscopic levels; draw conclusions from experimental results, identify and explain experimental procedures that are aligned to a question, and analyze sources of error; analyze a system with quantitative reasoning; and support claims with evidence and reasoning.OPEN BOOK FORMATConsider preparing single-page documents for each unit. Include key vocabulary and overarching themes. You will not have enough time during the exam to search through all of your notes for answers, so begin condensing and organizing them down.ADDITIONAL INFORMATIONBoth prompts will only cover Units 1–7 (including basic acid/base chemistry from Unit 4). Practice answering questions from released FRQs from years 2016–2019. You can access those here: https://apcentral.collegeboard.org/courses/ap-chemistry/exam. For additional information about the exam, visit the College Board website: https://apcoronavirusupdates.collegeboard.org/

DATE TIMEThursday, May 14

8:00am Hawaii 10:00am Alaska11:00am Pacific12:00pm Mountain1:00pm Central 2:00pm Eastern

MAKE-UP EXAMAvailable with permission from your school.

Tuesday, June 2

10:00am Hawaii 12:00pm Alaska1:00pm Pacific2:00pm Mountain3:00pm Central 4:00pm Eastern

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