Half Life

Which radioisotopes have the same decay mode and have half lives grater than 1 hour?

• As-198 and N-16

• Ca-37 and Fe-53

• I-131 and P-32

• Tc-99 and U-233

Based on Reference Table N, what fraction of a radioactive Sr-90 sample would remain unchanged after 56.2 years?

• 1/2

• 1/4

• 1/8

• 1/16

Based on Reference Table N, what fraction of a sample of gold-198 remains radioactive after 2.69 days?

• 1/4

• 1/2

• 3/4

• 7/8

According to Reference Table N, which radioactive isotope will retain only 1/8 its original atoms after approximately 43 days?

• gold-198

• iodine-131

• phosphorus-32

• radon-222

What is the total number of grams of a 32 gram sample of P-32 remains after 71.5 days of decay?

• 1.0 g

• 2.0 g

• 8.0 g

• 4.0 g

What mass of a 60 g sample of N-16 will remain unchanged after 28.8 seconds?

• 3.75 g

• 7.50 g

• 15.0 g

• 30.0 g

What total mass of a 16 gram sample of Co-60 will remain unchanged after 15.9 years?

• 1.0 g

• 2.0 g

• 8.0 g

• 4.0 g

Which sample will decay least over a period of 30 days?

• 10 g of Au-198

• 10 g of I-131

• 10 g of P-32

• 10 g of Rn-222

Compared to the half-life and decay mode of the nuclide Sr-90, the nuclide Ra-226

• a longer half life and the same decay mode

• a longer half life and the different decay mode

• a shorter half life and the same decay mode

• a shorter half life and the different decay mode

The half life of a radioactive isotope is 20.0 minutes. what is the total amount of a 1.00 gram sample of this isotope remaining after 1.00 hour?

• 0.500 g

• 0.333 g

• 0.250 g

• 0.125 g