chapter21part3

1)Which one of the following can be done to shorten the half-life of the radioactive decay of uranium-238?

• A) freeze it

• B) heat it

• C) convert it to UF6

• D) oxidize it to the +2 oxidation state

• E) none of the above

2)The beta decay of cesium-137 has a half-life of 30.0 years. How many years must pass to reduce a 25 mg sample of cesium 137 to 8.7 mg?

• A) 46

• B) 32

• C) 3.2

• D) 50

• E) 52

3) The half-life of 218Po is 3.1 minutes. How much of a 155 gram sample remains after 0.40 hours?

• A) 0.00067 g

• B) 0.0072 g

• C) 0.72 g

• D) 0.0047 g

• E) none of the above

4)Cesium-131 has a half-life of 9.7 days. What percent of a cesium-131 sample remains after 60 days?

• A) 100

• B) 0

• C) 1.4

• D) 98.6

• E) more information is needed to solve the problem

5) The half-life for beta decay of strontium-90 is 28.8 years. A milk sample is found to contain 10.3 ppm strontium-90. How many years would pass before the strontium-90 concentration would drop to 1.0 ppm?

• A) 92.3

• B) 0.112

• C) 186

• D) 96.9

• E) 131

6) The half-life of carbon-11 is 20.3 minutes. How much of a 100.0 mg sample remains after 1.50 hours?

• A) 8.48 mg

• B) 4.63 mg

• C) 12.9 mg

• D) 22.6 mg

• E) 7.70 mg

7)The half-life of 131I is 0.220 years. How much of a 500.0 mg sample remains after 24 hours?

• A) 496 mg

• B) 560 mg

• C) 219 mg

• D) 405 mg

• E) 337 mg

8)The half-life of 223Ra is 11.4 days. How much of a 200.0 mg sample remains after 600 hours?

• A) 0.219 mg

• B) 21.9 mg

• C) .0302 mg

• D) 43.8 mg

• E) 6.04 mg

9)The half-life of 222Rn is 3.80 days. If a sample contains 36.0 g of Rn-222, how many years will it take for the sample to be reduced to 1.00 mg of Rn-222?

• A) 19.7

• B) 0.1597

• C) 8.53

• D) 0.0234

• E) none of the above

10)The carbon-14 dating method can be used to determine the age of a

• A) flint arrowhead.

• B) papyrus scroll.

• C) stone axe head.

• D) clay pot.

• E) rock.