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Chapter 42: Q 23 Exercise (page 1236)

The half-life of 60Co is 5.27 years. The activity of a 60Co

sample is 3.50 x 109 Bq. What is the mass of the sample?

Short Answer

Expert verified

Hence the mass of the sample is :8.361×10-8kg

Step by step solution

01

Given information

t1/2=5.27yearsR=3.50×109Bq

02

Explanation

We will use the formula:

R=r·N→(Equation 1.)

First, we must determine the value of the decay rate r:

r=1τr=ln(2)t1/2r=0.6935.27×3.15×107sr=0.6931.663×108sr=4.17×10-9s

Next, we must determine the value of N using equation 1:

R=r·NN=RrN=3.50×109decays/s4.17×10-9sN=8.39×1017atoms

03

Explanation

Finally, we will find the mass:

M=m·NM=60×1.661×10-27kg×8.39×1017M=8.361×10-8kg

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Most popular questions from this chapter

A sample contains radioactive atoms of two types, A and B. Initially there are five times as many A atoms as there are B atoms. Two hours later, the numbers of the two atoms are equal. The half-life of A is 0.50 hour. What is the half-life of B?

The half-life of the uranium isotope U235is 700million years. The earth is approximately localid="1650486537957" 4.5billion years old. How much more U235was there when the earth formed than there is today? Give your answer as the then-to-now ratio.

A 115mCiradioactive tracer is made in a nuclear reactor. When it is delivered to a hospital hours later its activity is 95mCi. The lowest usable level of activity is 10mCi.

A. What is the tracer’s half-life?

B. For how long after delivery is the sample usable?

The activity of a sample of the cesium isotope 157Cs, with a half-life of 30 years, is 2.0×108Bq. Many years later, after the sample has fully decayed, how many beta particles will have been emitted?

You learned in Chapter 41 that the binding energy of the electron in a hydrogen atom is 13.6eV.

a. By how much does the mass decrease when a hydrogen atom is formed from a proton and an electron? Give your answer both in atomic mass units and as a percentage of the mass of the hydrogen atom.

b. By how much does the mass decrease when a helium nucleus is formed from two protons and two neutrons? Give your answer both in atomic mass units and as a percentage of the mass of the helium nucleus.

c. Compare your answers to parts a and b. Why do you hear it said that mass is “lost” in nuclear reactions but not in chemical reactions?
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