1. Suppose that you are given a 100 gram sample of a radioactive substance with

Question

1. Suppose that you are given a 100 gram sample of a radioactive substance with a half-life of 32 days. How many grams will be left after 192 days?

2. A radioactive substance is found to register 1000 counts per second on a Geiger counter. Twenty-four hours later it registers 125 counts per second. What is its half-life?

3. If a sample emits 1000 counts per second when the detector is 1 meter from the sample, how many counts per second would be observed when the detector is 2 meters from the sample?

4. Using the sample in question 3, how many counts per second would be observed when the detector is 10 meters away from the sample?

5. If a 20 gram sample of a radioactive substance has a half-life of 6000 years, how many grams would be present after 18000 years?

6. If Nitrogen-14 absorbs an alpha particle and then emits a Hydrogen-1, what is the resulting nucleus?

7. If Au-185 emits an alpha particle, what is the nucleus formed?

8. What nucleus emits an alpha particle and forms Th-234?

9. If Th-234 emits a beta particle, what nucleus is formed?

10. If Nitrogen-14 absorbs a neutron and then emits a Hydrogen-1, what nucleus is formed?

Explanation / Answer

ans 1 )

we know N/No = (1/2) ^n

192 day means 6 half lives

(1/2)^6 = 1/64

100/64 = 1.5625 g left

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