Chapter 20 Test

Question 1

Let’s examine an alpha emission reaction.

238 92 U -> 234 90 Th + 4 2 He

Which of the following statements about this event is not correct?

Answer 1

There is a mass difference of 4 between the two elements and a charge difference of 4 between the two elements.

Question 2

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

What would be the correct predicted behavior for a hypothetical isotope of 10 4 Be?

Answer 2

It will decay to 10 5 B by Beta emission

Question 3

Which statement about the decay of 14 C 6 is not correct?

Answer 3

Inside the nucleus of 14 6 C, a proton is changed into a neutron

Question 4

You are given a worked wooden item from an archaeological dig believed to date to during the last glaciation. As such, the artifact would be another piece of evidence in favor of the hypothesis that North America was settled prior to the end of the last glaciation. You analyse the artifact and find that it has a specific activity of 2.2 dpm/g. How old is the artifact?

Answer 4

16,000 y

Question 5

Suppose that you have 0.15 moles of a hypothetical isotope H. If k for the isotope is 0.055 / y, how many moles of the isotope are left after 2.5 years, and what is the half-life for the substance?

Answer 5

N2.5 y = 0.13 moles;

t½ = 12.6 y.

Question 6

A sample of 245Am has a t½ of 7.37 × 103 y and an activity value, A, of 1.00 Bq. How many nuclei are there initially and after 1,000 years? Use the following expressions to help you find your answer:
t½ = ln (2) / k;
N=A / k = A (t½ ) / ln (2) = A (t½ ) / 0.693.
Nt = Ni e−k t.

Answer 6

Ni = 3.35 × 1011 nuclei;
N1000 = 3.05 × 1011 nuclei.

Question 7

Suppose that a rock contains 0.539 mg of 206Pb. If the current rock specimen contains 2.035 mg of 238U, how many mg of 238U were in the original rock specimen?

Answer 7

2.658 mg

Question 8

Which statement about transuranium elements is not correct?

Answer 8

Transuranium elements are not difficult to produce.

Question 9

Radon (222Rn), a dense, noble gas, is commonly found in basements in some areas of the United States. Radon is a daughter of 238U decay. Which statement about radon is not correct?

Answer 9

222Rn, when ingested, changes to polonium (218Po), a solid. This is normally flushed out of the body.

Question 10

Critical mass is ___________________

Answer 10

the smallest amount of fissionable material needed to sustain a nuclear chain reaction

Question 11

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 11

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

Question 12

Which of the following correctly shows an alpha-emission reaction?

Answer 12

222 86 Rn -> 218 84 Po + 4 2 He

Question 13

What is the missing particle, P, that is necessary to balance the following nuclear reaction?
238 92 U -> 234 90 Th + P

Answer 13

4 2 He

Question 14

Binding energy is the ___________________

Answer 14

energy needed to release the nucleons in a nucleus

Question 15

The following reaction shows how one atom of 20 10 Ne is formed from protons, neutrons, and electrons. What is the value for Δm for this reaction?
10 1 1 p + 10 1 0 n + 10 0 -1 e -> 20 10 Ne
The mass of an electron is 0.00055 AMU
The mass of a proton is 1.00728 AMU
The mass of a neutron is 1.00866 AMU
The mass of 20 10 Ne is 19.9924 AMU

Answer 15

−0.1725 AMU

Question 16

A breeder reactor is a nuclear reactor _________________

Answer 16

that produces a useful, isotopic fuel.

Question 17

What do scientists theorize about the presence of uranium (and other isotopes larger than nickel).

Answer 17

A sudden input of energy from a supernova explosion causes the isotopes to form

Question 18

Plasma, with respect to fusion reactions, is __________________

Answer 18

a high-energy ionized gaseous mixture

Question 19

What process produces energy in the sun?

Answer 19

Fusion of atomic nuclei

Question 20

A fusion reaction is ___________________

Answer 20

an exothermic reaction in which two nuclei combine to produce a heavier nucleus

Question 21

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 21

2,506 y

Question 22

Which choice best defines the specific activity?

Answer 22

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

Question 23

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 23

9.7 x 10^9

Question 24

A free radical is _____________________

Answer 24

a reactive species with an unpaired valence electron

Question 25

Which statement about nuclear particles is not true?

Answer 25

ΔE = mc^2, c = 2.9979 × 10^8 ms−1