Regents Chemistry Test Preparation Practice

    Isotopes Atomic Mass

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    Base your answers to questions 9 on the information below and on your knowledge of chemistry.

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

    isotopes-atomic-mass fig: chem62019-exam_g13.png

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    Base your answers to questions 10 on the information below and on your knowledge of chemistry.

    Some isotopes of neon are Ne-19, Ne-20, Ne-21, Ne-22, and Ne-24. The neon-24 decays by beta emission. The atomic mass and natural abundance for the naturally occurring isotopes of neon are shown in the table below.

    mode-and-rate-of-decay fig: chem12019-exam_g12.png

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

    The table below shows data for three isotopes of the same element.

    isotopes-atomic-mass fig: chem82018-exam_g8.png

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    Base your answers to questions 12 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.

    isotopes-atomic-mass 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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    Base your answers to questions 13 on the information below and on your knowledge of chemistry.

    The diagrams below represent four different atomic nuclei.

    identification-of-element fig: chem62017-exam_g21.png

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

    Illuminated EXIT signs are used in public buildings such as schools. If the word EXIT is green, the sign may contain the radioisotope tritium, hydrogen-3. The tritium is a gas sealed in glass tubes. The emissions from the decay of the tritium gas cause a coating on the inside of the tubes to glow.

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

    Iodine has many isotopes, but only iodine-127 is stable and is found in nature. One radioactive iodine isotope, I-108, decays by alpha particle emission. Iodine-131 is also radioactive and has many important medical uses.

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