Regents Chemistry Test Preparation Practice

    Mode And Rate Of Decay

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    Base your answers to questions 10 on the information below.

    Nuclear radiation is harmful to living cells, particularly to fast-growing cells, such as cancer cells and blood cells. An external beam of the radiation emitted from a radioisotope can be directed on a small area of a person to destroy cancer cells within the body.

    Cobalt-60 is an artificially produced radioisotope that emits gamma rays and beta particles. One hospital keeps a 100.0-gram sample of cobalt-60 in an appropriate, secure storage container for future cancer treatment.

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    Base your answers to questions 11 on the information below and on your knowledge of chemistry.

    In 1896, Antoine H. Becquerel discovered that a uranium compound could expose a photographic plate wrapped in heavy paper in the absence of light. It was shown that the uranium compound was spontaneously releasing particles and high-energy radiation. Further tests showed the emissions from the uranium that exposed the photographic plate were not deflected by charged plates.

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    Base your answers to questions 12 on the information below and on your knowledge of chemistry.

    Cobalt-60 is an artificial isotope of Co-59. The incomplete equation for the decay of cobalt-60, including beta and gamma emissions, is shown below.

    atomic-concepts, isotopes-atomic-mass, periodic-table, identification-of-element fig: chem62019-exam_g13.png

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    Base your answers to questions 13 on the information below and on your knowledge of chemistry.

    One fission reaction for U-235 is represented by the balanced nuclear equation below.

    nuclear-chemistry, nuclear-reactions fig: chem82015-exam_g9.png

    Both radioisotopes produced by this fission reaction undergo beta decay. The half-life of Xe-140 is 13.6 seconds and the half-life of Sr-94 is 1.25 minutes.

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    Base your answers to questions 14 on the information below and on your knowledge of chemistry.

    Radioactive emissions can be detected by a Geiger counter. When radioactive emissions enter the Geiger counter probe, which contains a noble gas such as argon or helium, some of the atoms are ionized. The ionized gas allows for a brief electric current. The current causes the speaker to make a clicking sound. To make sure that the Geiger counter is measuring radiation properly, the device is tested using the radioisotope Cs-137.

    To detect gamma radiation, an aluminum shield can be placed over the probe window, to keep alpha and beta radiation from entering the probe. A diagram that represents the Geiger counter is shown below.

    periodic-table, characteristic-trends fig: chem82019-exam_g13.png

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    Base your answers to questions 15 on the information below and on your knowledge of chemistry.

    The diagram below shows the first three steps in the uranium-238 radioactive decay series.

    atomic-concepts, isotopes-atomic-mass, periodic-table, identification-of-element fig: chem12018-exam_g15.png

    The decay mode for the first and third steps is shown above the arrows. The decay mode for the second step is not shown in the diagram. Thorium-234 has a half-life of 24.10 days.

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