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The graph below shows the radioactive decay of an isotope of strontium. Based on the graph, what is the half-life of strontium? (4 points)

The graph below shows the radioactive decay of an isotope of carbon. Based on the graph, what is the half-life of carbon? (4 points)

Which of the following is true about the origin of the salts in Earth’s oceans? (2 points)

As potassium-40 decays, it becomes argon-40, as shown in the following graph. Public Domain Potassium-40 has a half-life of approximately 1.25 billion years. Approximately how many years will pass before a sample of potassium-40 contains one-eighth the original amount of parent isotope? (2 points)

The following graph shows the rates of decay for four parent isotopes. Based on the graph, which parent isotope most likely has a half-life of 4.5 billion years? (2 points) Public Domain

The diagram below shows a portion of the geologic time scale. Which of these is the most likely inference that can be drawn from the time scale? (4 points)

The following table shows the currently accepted half-life values for six parent isotopes. Parent Isotope Currently Accepted Half-Life Values Uranium-238 4.5 billion years Uranium-235 704 million years Thorium-232 14.0 billion years Rubidium-87 48.8 billion years Potassium-40 1.25 billion years Samarium-147 106 billion years Earth is approximately 4.5 billion years old. Given this information and the data in the table, which isotope—if present at Earth’s creation—would currently be approaching its fourth half-life? (2 points)

As potassium-40 decays, it becomes argon-40, as shown in the following graph. Public Domain Potassium-40 has a half-life of approximately 1.25 billion years. Approximately how many years will pass before a sample of potassium-40 contains one-sixteenth the original amount of parent isotope? (2 points)

The table below shows the right ascensions of two stars at a location. Name of star Right ascension Star 1 2 hour Star 2 2 hour 30 minutes What is the interval between the times when the two stars rise at the location? (3 points)

The following graph shows the rates of decay for four parent isotopes. Based on the graph, which parent isotope most likely has a half-life of 600 million years? (2 points) Public Domain