University Physics Volume 3

75.

The wiki-phony site states that the atomic mass of chlorine is 40 g/mol. Check this result. Hint: The two, most common stable isotopes of chlorine are: $1735Cl1735Cl$ and $1737Cl1737Cl$. (The abundance of Cl-35 is $75.8%75.8%$, and the abundance of Cl-37 is $24.2%24.2%$.)

76.

A particle physicist discovers a neutral particle with a mass of 2.02733 u that he assumes is two neutrons bound together.

(a) Find the binding energy.

77.

A nuclear physicist finds $1.0μg1.0μg$ of $236U236U$ in a piece of uranium ore (T1/2 = $2.348×107y2.348×107y$). (a) Use the decay law to determine how much $236U236U$ would had to have been on Earth when it formed $4.543×109y4.543×109y$ ago for $1.0μg1.0μg$ to be left today. (b) What is unreasonable about this result? (c) How is this unreasonable result resolved?

78.

A group of scientists use carbon dating to date a piece of wood to be 3 billion years old. Why doesn’t this make sense?

79.

According to your lab partner, a 2.00-cm-thick sodium-iodide crystal absorbs all but $10%10%$ of rays from a radioactive source and a 4.00-cm piece of the same material absorbs all but $5%?5%?$ Is this result reasonable?

80.

In the science section of the newspaper, an article reports the efforts of a group of scientists to create a new nuclear reactor based on the fission of iron (Fe). Is this a good idea?

81.

The ceramic glaze on a red-orange “Fiestaware” plate is $U2O3U2O3$ and contains 50.0 grams of $238U238U$, but very little $235U235U$. (a) What is the activity of the plate? (b) Calculate the total energy that will be released by the $238U238U$ decay. (c) If energy is worth 12.0 cents per $kW·hkW·h$, what is the monetary value of the energy emitted? (These brightly-colored ceramic plates went out of production some 30 years ago, but are still available as collectibles.)

82.

Large amounts of depleted uranium $(238U)(238U)$ are available as a by-product of uranium processing for reactor fuel and weapons. Uranium is very dense and makes good counter weights for aircraft. Suppose you have a 4000-kg block of $238U238U$. (a) Find its activity. (b) How many calories per day are generated by thermalization of the decay energy? (c) Do you think you could detect this as heat? Explain.

83.

A piece of wood from an ancient Egyptian tomb is tested for its carbon-14 activity. It is found to have an activity per gram of carbon of $A=10decay/min·gA=10decay/min·g$. What is the age of the wood?