Regents Chemistry Table and Half Life

What is Half-life?

• The amount of time it takes for some of the nuclei in a sample of the isotope to decay
• The amount of time it takes for half the electrons in a sample of the isotope to decay
• The amount of time it takes for half the nuclei in a sample of the isotope to decay
• the amount of time it takes to double the nuclei in a sample of the isotope to decay

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NGSS.HS-PS1-8

The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?

• 100.0g
• 50.0g
• 12.5g
• 8.5g

After the third half-life, how much of a radioactive sample is left?

• 1/2
• 1/3
• 1/16
• 1/8

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NGSS.HS-PS1-8

The half life of iodine-131 is 8 days. What fraction of an iodine-131 sample will remain after 40 days?

• 1/2
• 1/64
• 1/5
• 1/32

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NGSS.HS-PS1-8

As a sample of Neon-19 undergoes radioactive decay, its half-life will

• decrease
• increase
• remain the same
• start over

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NGSS.HS-PS1-8

Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained. If it takes 10 minutes to set up an experiment using barium-122, how much barium-122 will be left when the experiment begins?

• 0.25g
• 2.5g
• 25g
• 80g

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NGSS.HS-PS1-8

When nuclei decay, massive amounts of __________ is released.

• energy
• electrons
• protons
• neutrons

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NGSS.HS-PS1-8

If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?

• 1 half-life
• 2 half-lives
• 3 half-lives
• 4 half-lives

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NGSS.HS-PS1-8

The half-life of a radioactive isotope is not effected by which of the following?

• Temperature
• Pressure
• Concentration
• None of these will effect the rate of a nuclear reaction

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NGSS.HS-PS1-8

After 4 half-lives, 1g of a sample of Krypton-85 remains unchanged.  What was the original mass of the sample?

• 16g
• 32g
• 0.0625g
• 4g

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NGSS.HS-PS1-8