Chapter 20 Homework

Question 1

What process produces energy in the sun?

Answer 1

Fusion of atomic nuclei

Question 2

Which choice best defines the specific activity?

Answer 2

The specific activity is the number of disintegrations / per gram.

Question 3

Binding energy is the ___________________

Answer 3

energy needed to release the nucleons in a nucleus.

Question 4

The metalloid astatine (At) is the heaviest halogen. All of its known isotopes are radioactive, with the longest-lived isotope, 210At, having a half-life of 8.3 hours. The rapid decay of astatine makes it useful in treating cancer. How much 210At will remain after 48 hours if the initial sample had a mass of 10 g?

Answer 4

0.183 g

Question 5

Look at the chart that shows the stability of an isotope as a function of the number of neutrons and protons.

Which one of the following isotopes is stable?

Answer 5

16 8 O

Question 6

Look at the lengthy decay reaction for 238 92 U. Which statement about this chain of reactions is not correct?

Answer 6

210Pb will readily decay by beta emission to form 210Bi

Question 7

We learned that ΔE = Δmc2. Which statement related to this expression is not correct?

Answer 7

The term Δm is the mass of reactants less the mass of products.

Question 8

Which of the following nuclear reactions is not correctly balanced?

Answer 8

21 9 F -> 21 10 Ne + 4 2 He

Question 9

Which statement about nuclear binding energy per nucleon is not correct?

Answer 9

235U has the greatest value for Eb per nucleon

Question 10

You have a sample of bone collected from Nevada and you find that it contains strontium-90 and exhibits an activity of 2.5 Bq. How much strontium-90 was present in the bone when the animal died 45 years ago? (The half-life of 90Sr is 29 years.)

Answer 10

9.7 x 10^9

Question 11

The half-life of tritium is 12.3 y. What is the first order rate constant, k, for tritium?

Answer 11

0.056/y

Question 12

Which of the following statements about an electron capture reaction is not correct?

Answer 12

An electron capture reaction is characterized by a nucleus capturing a positron from the nucleus.

Question 13

How old is an object whose current specific activity is 11.3 dpm/g? Remember that for a living organism, the specific activity is 15.3 dpm/g. For 14 7 C decay, t1/2 = 5,730 y

Answer 13

2,506 y

Question 14

Which of the following statements about a beta emission reaction is not correct?

Answer 14

7 4 Be + 0 -1 e -> 7 3 Li is an example of a beta emission reaction

Question 15

Suppose that a rock contains 0.598 mg of 206Pb. If the current rock specimen contains 2.345 mg of 238U, how old is the rock specimen? (t½ of 238U = 4.5 × 109 y)

Answer 15

1.68 × 10^9 y

Question 16

Which statement about fission reactions is not true?

Answer 16

A fission reaction can produce a limited amount of CO2, which adds to the greenhouse effect.

Question 17

Scientists theorize that eventually all of the1H in the sun will be converted to4He. Which statement based on this theory is not correct?

Answer 17

The sun will cool considerably

Question 18

6LiD is currently being investigated as a fuel source for fusion reactors. It is involved in a 2-step fusion reaction
Step 1: 6LiD + 1 0 n -> 3 1 H + 4 2 He
Step 2: 2 1 H + 3 1 H -> 4 2 He + 1 0 n
Which statement about this event is not correct?

Answer 18

This is not a self-sustaining reaction.

Question 19

Look at the radioactive decay reaction for 232 90 Th
232 90 Th -> 228 88 Ra + 4 2 He
Which of the following statements about this event is not correct?

Answer 19

The element thorium is located two positions to the left of radium in the periodic table of elements.

Question 20

Which statement about the hydroxyl radical ( • OH) is not correct?

Answer 20

• OH is very particular about which hydrogen atom it gains in living tissue