Page 359 - Teacher Preview Copy
P. 359
.
Topic 12: Nuclear Chemistry
17. Half-Life Problems: Determining length of time
1. What is the total number of hours required for potassium – 42 to undergo 2 half-life periods?
1) 6.2 hours 2) 12.4 hours 3) 24.8 hours 4) 37.2 hours
131
2. I will go through 4 half-life periods in approximately how many days?
1) 32 days 2) 2 days 3) 24 days 4) 12 days
3. Sr-90 undergoes 2 half-life periods in approximately
1) 14 years 2) 28 years 3) 30 years 4) 56 years
4. The half life of a radioisotope X is 30 days. In how many days will X undergo 3 half –life periods?
Teacher Preview Copy
1) 3 days 2) 90 days 3) 10 days 4) 33 days?
5. Exactly how much time elapse before 16 grams of potassium-42 decays, leaving 2 grams of the
original isotope?
1) 99.2 hours 2) 24.8 hours 3) 37.2 hours 4) 49.6 hours
6. How many days are required for a 200 gram sample of Radon-222 to decay to 50.0 grams?
1) 1.91 2) 3.82 3) 7.64 4) 11.5
7. How long will it take for Fr to decay from 50 grams to 12.5 grams?
220
1) 27.5 s Teacher Preview Copy 4) 110 s
3) 343.75 s
2) 45 s
8. In how many years would a radioisotope with a half life of 15 years decays from an original mass
of 32 grams to 2 grams?
1) 480 years 2) 64 years 3) 60 years 4) 30 years
9. In approximately how many days would a 12 gram sample of Iodine -131 decays leaving only 3
grams of the original isotope remaining ?
1) 1 x 8 days 2) 2 x 8 days 3) 3 x 8 days 4) 4 x 8 days
10. The half-life of a radioisotope is 30 seconds. Which set up is correct for calculating the total
length of time it takes for a 50 g sample of this isotope to decay to 3.125 g?
1) 30 x 3.125 2) 30 ÷ 3.125 3) 30 x 4 4) 30 ÷ 4
Copyright©2010 E3 Scholastic Publishing. All Rights Reserved. SurvivingChem.com 349
Topic 12: Nuclear Chemistry
17. Half-Life Problems: Determining length of time
1. What is the total number of hours required for potassium – 42 to undergo 2 half-life periods?
1) 6.2 hours 2) 12.4 hours 3) 24.8 hours 4) 37.2 hours
131
2. I will go through 4 half-life periods in approximately how many days?
1) 32 days 2) 2 days 3) 24 days 4) 12 days
3. Sr-90 undergoes 2 half-life periods in approximately
1) 14 years 2) 28 years 3) 30 years 4) 56 years
4. The half life of a radioisotope X is 30 days. In how many days will X undergo 3 half –life periods?
Teacher Preview Copy
1) 3 days 2) 90 days 3) 10 days 4) 33 days?
5. Exactly how much time elapse before 16 grams of potassium-42 decays, leaving 2 grams of the
original isotope?
1) 99.2 hours 2) 24.8 hours 3) 37.2 hours 4) 49.6 hours
6. How many days are required for a 200 gram sample of Radon-222 to decay to 50.0 grams?
1) 1.91 2) 3.82 3) 7.64 4) 11.5
7. How long will it take for Fr to decay from 50 grams to 12.5 grams?
220
1) 27.5 s Teacher Preview Copy 4) 110 s
3) 343.75 s
2) 45 s
8. In how many years would a radioisotope with a half life of 15 years decays from an original mass
of 32 grams to 2 grams?
1) 480 years 2) 64 years 3) 60 years 4) 30 years
9. In approximately how many days would a 12 gram sample of Iodine -131 decays leaving only 3
grams of the original isotope remaining ?
1) 1 x 8 days 2) 2 x 8 days 3) 3 x 8 days 4) 4 x 8 days
10. The half-life of a radioisotope is 30 seconds. Which set up is correct for calculating the total
length of time it takes for a 50 g sample of this isotope to decay to 3.125 g?
1) 30 x 3.125 2) 30 ÷ 3.125 3) 30 x 4 4) 30 ÷ 4
Copyright©2010 E3 Scholastic Publishing. All Rights Reserved. SurvivingChem.com 349
