5 Steps to a 5 AP Chemistry 2019

AP Chemistry Practice Exam 1 ❮ 311

The AP exam is a timed exam; keep this in mind as you prepare. When taking the

various tests presented in this book, you should follow the AP exam rules as closely as

possible. Anyone can improve his or her score by using notes, books, or an unlimited

time. You will have none of these on the AP exam, so resist the temptation to use

them on practice exams. Carefully time yourself, do not use other materials, and use

a calculator only when expressly allowed to do so. After you have finished an exam,

you may use other sources to go over questions you missed or skipped. We have seen

many students get into trouble because the first time they attempted a test under

“test conditions” was on the test itself.

AP Chemistry Practice Exam 1, Section I (Multiple Choice)

Time—1 hour and 30 minutes

NO CALCULATOR MAY BE USED WITH SECTION I

Answer the following questions in the time allowed. You may use the periodic table in the back of the book.

Use the following information to answer

questions 1–7.

Sodium azide, NaN 3 , is a component of automo-

bile airbags. It is useful because it quickly decom-

poses to generate a large volume of nitrogen gas.

The balanced chemical equation for the reaction is:

2 NaN 3 (s) → 2 Na(s) + 3 N 2 (g)

There are additional components in the airbag to

react with the elemental sodium formed.

Sodium azide is an unstable compound; therefore,

it is often necessary to analyze samples as a check of

its purity. A chemist is attempting to develop a new

analytical, which employs the following reaction:

NaN 3 (aq) + Na 2 S(aq) + 3 H 2 O(l) → N 2 (g) +

NH 3 (g) + S(s) + 3 NaOH(aq)

The chemist weighed a small flask both with and

without a sample of sodium azide and recorded

the masses. Next, she connected the flask to the

system shown below.

The flask in the middle and the rubber tubing

leading to the beaker were completely filled with

dilute acid, and then the clamp was removed.

Excess sodium sulfide solution was added to the

flask containing the sample. The liquid level in the

second flask dropped as the generated nitrogen gas

displaced the water into the beaker. The system

was left intact until gas generation ceased. After

the system returned to room temperature, the

beaker was raised until the water in the beaker was

at the same level as in the second flask. When the

liquid levels were the same, the clamp was replaced

to prevent further transfer. The chemist completed

the following data table in her lab book.

Mass of empty flask 175.245 g

Mass of flask plus sodium azide 176.604 g

Volume of displaced water 315 mL

Barometric pressure 748.2 torr

Room temperature 27.0°C

Vapor pressure of water at

27.0°C

27.0 torr

(assumed to be

equal to that

of dilute acid)

GO ON TO THE NEXT PAGE

Rubber tubing

Sodium azide sample

Flask completely

filled with dilute acid

Empty beaker

Sodium sulfide solution

Clamp

20-Moore_PE01_p307-340.indd 311 31/05/18 1:58 pm