5 Steps to a 5 AP Chemistry

 Free-Response Questions

Answer the following questions. You have 15 minutes, and you may use a calculator and

the tables at the back of the book.

a. The bond energy of fluorine is 159 kJ/mol.

i. Determine the energy, in J, of a photon of light needed to break a F–F bond.

ii. Determine the frequency of this photon in s−^1.

iii. Determine the wavelength of this photon in nanometers.

b. Determine the wavelength, in m, of an alpha particle traveling at 5.2 × 107 m/s. An

alpha particle has a mass of 6.6 × 10 −^24 g.

c. Barium imparts a characteristic green color to a flame. The wavelength of this light is

551 nm. Determine the energy involved in kJ/mol.

 Answers and Explanations

a. Several of the equations given at the beginning of the exam are needed. In addition, the

values of Planck’s constant, Avogadro’s number, and the speed of light are needed.

These constants are also given on the exam.

i. This is a simple conversion problem:

Give yourself 1 point if you got this answer.

ii. This part requires the equation ΔE=hn:

Give yourself 1 point for this answer. If you got the wrong answer in the preceding

part, but used it correctly here (in place of the 2.64 × 10 −^19 J), you still get 1 point.

iii. The equation c=lnis needed.

Again, give yourself 1 point for the correct answer. If you correctly used a wrong

answer from the preceding part, you still get 1 point.

λ

ν

== ×

×

⎛

⎝

⎜

⎞

⎠

⎟

⎛

⎝

⎜

⎞

⎠

⎟=

c 30 10

398 10

10

1

8

14

.^9

.

m/s

s

nm

–1 m

7 75 10. ×^2 nm

ν==

×

×

=×

−

−

ΔE

h

264 10

663 10

398 10

19

34

. 14

.

.

J

Js

s–1

159

6 022 10

1000

(^231)
kJ
mol
1mol J
kJ

⎛

⎝

⎜

⎞

⎠

⎟

×

⎛

⎝

⎜

⎞

⎠

⎟

⎛

⎝

⎜

⎞

. ⎠

⎟⎟=×

264 10.J−^19

144  STEP 4. Review the Knowledge You Need to Score High