Chapter 29 Questions

Question 1

A neutral atom is designated as 39/19 X. How many protons, neutrons, and electrons does it have?

Answer 1

protons: 19
electrons: 19
neutrons: 20

Question 2

What fraction of a radioactive sample remains after one, two and three half lives have elapsed?

Answer 2

1. 0.5
2. 0.25
3. 0.125

Question 3

A radioactive sample has activity R. For each of the following, indicate whether activity would increase, decrease, or remain unchanged: the number of radioactive nuclei in the sample is doubled

Answer 3

the activity increases

Question 4

A radioactive sample has activity R. For each of the following, indicate whether activity would increase, decrease, or remain unchanged: the half life of the radioactive nuclei is doubled

Answer 4

the activity would decrease

Question 5

A radioactive sample has activity R. For each of the following, indicate whether activity would increase, decrease, or remain unchanged: the decay constant is doubled

Answer 5

the activity would increase

Question 6

A radioactive sample has activity R. For each of the following, indicate whether activity would increase, decrease, or remain unchanged: A time period equal to two half lives is allowed to elapse

Answer 6

the activity would decrease

Question 7

True or false, a radioactive atom always decays after two half lives are elapsed

Answer 7

false

Question 8

What fraction of a radioactive sample is DECAYED after 3 half lives elapse?

Answer 8

7/8

Question 9

Suppose the decay constant of substance A is twice that of substance B. If substance B has a half life of 4 hours, what is the half life of substance A?

Answer 9

2 hours

Question 10

If the Q value of an endothermic reaction is -2.17 MeV, what is the minimin kinetic energy needed in the reactant nuclei for the reaction to occur?

Answer 10

greater than 2.17 MeV

Question 11

decay reaction problem

Answer 11

add up the numbers on each side, they should be equal