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25.3 Half Life

Total questions: 91

Worksheet time: 4hrs 8mins

Name
Class
Date
1.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
2.

After 22,800 years, approximately what percentage of the original carbon-14 remains?

a)

15%

b)

12.5%

c)

6.25%

d)

3.125%

3.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
4.

The % of the parent isotope remaining after 1 Half Life.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

5.

The % of the parent isotope remaining after 2 Half Lives.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

6.

What is the Half life of this isotope?

a)

5 seconds

b)

10 seconds

c)

15 seconds

d)

20 seconds

7.

What is the Half Life of this isotope?

a)

3 days

b)

5 days

c)

8 days

d)

10 days

8.
What is Half-life?
a)
The amount of time it takes for some of the nuclei in a sample of the isotope to decay
b)
The amount of time it takes for half the electrons in a sample of the isotope to decay
c)
The amount of time it takes for half the nuclei in a sample of the isotope to decay
d)
the amount of time it takes to double the nuclei in a sample of the isotope to decay
9.
If one-fourth of the carbon-14 is remaining then how many half-lives have passed?
a)
1
b)
2
c)
3
d)
4
10.

Why do some elements have half-lives?

a)

they radioactively decay

b)

half of their atom gets stolen

c)

They are Twizzlers that break in half

11.

What is the only difference between two different isotopes of the same element?

a)

Number of neutrons

b)

Number of protons

c)

Number of electrons

d)

Size of atom

12.

The half-life of Element X is 2 years.


How long has passed if Element X has reduced by half 5 times?

a)

2 years

b)

4 years

c)

6 years

d)

8 years

e)

10 years

13.

After the third half-life, how much of the sample is left?

a)

1/2

b)

1/3

c)

1/16

d)

1/8

14.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
15.

The % of the parent isotope remaining after 2 Half Lives.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

16.

Half life (in radioactivity) is the amount of time it takes for half of a radioactive sample to

a)

split.

b)

combine.

c)

decay.

d)

become parent material.

17.

You have 100 grams of radioactive C-14. The half life of C-14 is 5730 years.

How many grams are left after 2 half lives?

a)

100 grams

b)

25 grams

c)

50 grams

d)

14 grams

18.

A certain radioactive sample has a half life of 2 years. After 6 years, how much of the sample is left?

a)

1/2

b)

1/3

c)

1/16

d)

1/8

19.

If Bromine has 35 protons and a mass of 80, how many neutrons does it have?

a)

35

b)

115

c)

45

20.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
21.

The % of the parent isotope remaining after 1 Half Life.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

22.

The % of the parent isotope remaining after 2 Half Lives.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

23.

What is the Half life of this isotope?

a)

5 seconds

b)

10 seconds

c)

15 seconds

d)

20 seconds

24.

What is the Half Life of this isotope?

a)

3 days

b)

5 days

c)

8 days

d)

10 days

25.
What is Half-life?
a)
The amount of time it takes for some of the nuclei in a sample of the isotope to decay
b)
The amount of time it takes for half the electrons in a sample of the isotope to decay
c)
The amount of time it takes for half the nuclei in a sample of the isotope to decay
d)
the amount of time it takes to double the nuclei in a sample of the isotope to decay
26.
If one-fourth of the carbon-14 is remaining then how many half-lives have passed?
a)
1
b)
2
c)
3
d)
4
27.

Why do some elements have half-lives?

a)

they radioactively decay

b)

half of their atom gets stolen

c)

They are Twizzlers that break in half

28.

What is the only difference between two different isotopes of the same element?

a)

Number of neutrons

b)

Number of protons

c)

Number of electrons

d)

Size of atom

29.

What is the Half life of this isotope?

a)

5 seconds

b)

10 seconds

c)

15 seconds

d)

20 seconds

30.

What is the Half Life of this isotope?

a)

3 days

b)

5 days

c)

8 days

d)

10 days

31.

What is the half-life of this sample?

(a)  

32.

What is the half-life of this sample?

(a)  

33.

What is the half life of this sample?

(a)  

34.

After 22,800 years, approximately what percentage of the original carbon-14 remains?

a)

15%

b)

12.5%

c)

6.25%

d)

3.125%

35.

What is the half-life of this sample?

(a)  

36.
If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.
a)
1.25mg
b)
1.25g
c)
10g
d)
10mg
37.
The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?
a)
3.0g
b)
0.25mg
c)
0.3g
d)
0.25g
38.

The % of the parent isotope remaining after 1 Half Life.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

39.

The % of the parent isotope remaining after 2 Half Lives.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

40.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
41.

What is the Half life of this isotope?

a)

5 seconds

b)

10 seconds

c)

15 seconds

d)

20 seconds

42.

What is the Half Life of this isotope?

a)

3 days

b)

5 days

c)

8 days

d)

10 days

43.

What is the half-life of this sample?

(a)  

44.

What is the half-life of this sample?

(a)  

45.

What is the half life of this sample?

(a)  

46.

What is the half-life of this sample?

(a)  

47.

If someone started off with a kilogram sample of this material, calculate how many grams of it would be remaining after half an hour.

Give your answer to two decimal places.

(a)  

48.

What is the half-life of this sample?

(a)  

49.

What would the activity of this sample be after 60 minutes?

Do not round your answer

(a)  

50.
If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.
a)
1.25mg
b)
1.25g
c)
10g
d)
10mg
51.
The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?
a)
3.0g
b)
0.25mg
c)
0.3g
d)
0.25g
52.
If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?
a)
1 half-life
b)
2 half-lives
c)
3 half-lives
d)
4 half-lives
53.

After 22,800 years, approximately what percentage of the original carbon-14 remains?

a)

15%

b)

12.5%

c)

6.25%

d)

3.125%

54.

The % of the parent isotope remaining after 1 Half Life.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

55.

The % of the parent isotope remaining after 2 Half Lives.

a)

50%

b)

25%

c)

12.5%

d)

6.25%

56.

The mass of a radioisotope falls from 1.6g to 0.1g in 2 hours. What is the half-life of this radioisotope (in minutes)?

(a)  

57.

If a 1g sample of a radioisotope with a half-life of 3 days has an activity of 32 counts sec-1, how long would it take for the activity of a 2g sample to fall to 8 counts sec-1?

Give your answer in days

(a)  

58.

A medical radioisotope has a half-life of 1.5 hours. Its radioactivity was recorded as 10,000 counts min-1 at 9am. What will the count rate be by 3pm?

(a)  

59.

Phosphorus-32 is a radioisotope with a half-life of 14.3 days. If you start with 4g of phosphorus-32, how many half-lives will have passed after 57.2 days? 

(a)  

60.

Sodium-24 has a half-life of 15 hours. How much sodium-24 will remain in an 18g sample after 60 hours?

Do not round your answer.

(a)  

61.

After 42 days, a 2.0g sample of phosphorus-32 contains only 0.25g of the isotope. What is the half-life of phosphorus-32?

(a)  

62.

Iodine-131 has a half-life of 8 days. What percentage of the sample would remain at the end of 32 days?

(a)  

63.

The half-life of chromium-51 is 28 days. If the sample contained 510 grams, how much Cr-51 would remain after 56 days?

(a)  

64.

If 20.0g of a radioisotope are present at 1pm and 5.0g remain at 2pm, what is the half-life of this isotope?

Give your answer in minutes.

(a)  

65.

The half-life of iodine-125 is 60 days. What percentage of iodine-125 would be left after 360 days?

Do not round your answer

(a)  

66.

The half-life of thorium-227 is 18.72 days. How many days are required for 4.68g to remain if you start with 74.88 grams?

Do not round your answer

(a)  

67.

If a source had an activity of 12 kBq and a half-life of 6 hours, what would the activity be after one day? Give your answer in Bq

(a)  

68.

A radioactive source had an activity of 1 MBq. After 30 days it had fallen to 62.5 kBq. Calculate the half-life of this sample.

(a)  

69.

A source with an activity of 300 Bq had a half-life of 14 days. The source was measured some time later and the activity was recorded as 9.375 Bq. How much time had passed?

(a)  

70.

A source has a half-life of 6 days. After 36 days the activity of the source had fallen to 7 Bq. What was the intial activity of the source?

(a)  

71.
After the third half-life, how much of the sample is left?
a)
1/2
b)
1/3
c)
1/16
d)
1/8
72.
If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.
a)
1.25mg
b)
1.25g
c)
10g
d)
10mg
73.
The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?
a)
3.0g
b)
0.25mg
c)
0.3g
d)
0.25g
74.
If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?
a)
1 half-life
b)
2 half-lives
c)
3 half-lives
d)
4 half-lives
75.

The diagram shows 32 atoms.

16 of the Red are parent isotopes

16 of the Green are daughter isotopes

How many half-lives have occurred?

a)

0

b)

1

c)

2

d)

3

76.
What type of decay is being illustrated in following picture? 
a)
beta decay
b)
alpha decay 
77.
You have 100 grams of radioactive C-14. The half life of C-14 is 5730 years. 
How many grams are left after 1 half life? 
a)
100 grams
b)
25 grams
c)
2 grams
d)
50 grams
78.
What is Half-life?
a)
The amount of time it takes for some of the nuclei in a sample of the isotope to decay
b)
The amount of time it takes for half the electrons in a sample of the isotope to decay
c)
The amount of time it takes for half the nuclei in a sample of the isotope to decay
d)
the amount of time it takes to double the nuclei in a sample of the isotope to decay
79.
When nuclei decay, massive amounts of __________ is released.
a)
energy
b)
jello
c)
protons
d)
neutrons
80.

The diagram shows 32 atoms

32 of the Red are the parent isotope

0 of the atoms are daughter isotopes

How many half-lives have occurred?

a)

0

b)

1

c)

2

d)

3

81.
If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.
a)
1.25mg
b)
1.25g
c)
10g
d)
10mg
82.
The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?
a)
3.0g
b)
0.25mg
c)
0.3g
d)
0.25g
83.
You have 100 grams of radioactive C-14. The half life of C-14 is 5730 years. 
How many grams are left after 1 half life? 
a)
100 grams
b)
25 grams
c)
2 grams
d)
50 grams
84.
What is Half-life?
a)
The amount of time it takes for some of the nuclei in a sample of the isotope to decay
b)
The amount of time it takes for half the electrons in a sample of the isotope to decay
c)
The amount of time it takes for half the nuclei in a sample of the isotope to decay
d)
the amount of time it takes to double the nuclei in a sample of the isotope to decay
85.
When nuclei decay, massive amounts of __________ is released.
a)
energy
b)
jello
c)
protons
d)
neutrons
86.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
87.

What is the Half life of this isotope?

a)

5 seconds

b)

10 seconds

c)

15 seconds

d)

20 seconds

88.

What is the Half Life of this isotope?

a)

3 days

b)

5 days

c)

8 days

d)

10 days

89.

Radioactive carbon-14 is often useful in determining the absolute age of geologic samples because radioactive isotopes

a)

decay at a regular rate

b)

become less stable during decay

c)

remain unchanged over time

d)

stabilize after four half-lives

90.
What is the half-life of iodine-131?
a)
32 days
b)
8 days
c)
16 days
d)
24 days
91.
What is Half-life?
a)
The amount of time it takes for some of the nuclei in a sample of the isotope to decay
b)
The amount of time it takes for half the electrons in a sample of the isotope to decay
c)
The amount of time it takes for half the nuclei in a sample of the isotope to decay
d)
the amount of time it takes to double the nuclei in a sample of the isotope to decay

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