13-02: Half-life

Based on Table N, uranium-238 and uranium-235 have different

• decay modes

• half-lives

• numbers of protons

• number of electrons

Tags

NGSS.HS-PS1-8

What is the mass of an original 5.60-gram sample of iron-53 that remains unchanged after 25.53 minutes?

• 0.35 g

• 0.70 g

• 1.40 g

• 2.80 g

Tags

NGSS.HS-PS1-7

A radioactive isotope has a half-life of 2.5 years. Which fraction of the original mass remains unchanged after 10 years?

• 1/2

• 1/4

• 1/8

• 1/16

Tags

NGSS.HS-PS1-8

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

• a longer half-life and the same decay mode

• a longer half-life and a different decay mode

• a shorter half-life and the same decay mode

• a shorter half-life and a different decay mode

Tags

NGSS.HS-PS1-8

After decaying for 48 hours, 1/16 of the original mass of a radioisotope sample remains unchanged. What is the half-life of this radioisotope?

• 3.0 h

• 9.6 h

• 12 h

• 24 h

Tags

NGSS.HS-PS1-8

What fraction of a Sr-90 sample remains unchanged after 87.3 years?

• 1/2

• 1/3

• 1/4

• 1/8

Tags

NGSS.HS-PS1-8

What is the half-life of a radioisotope if 25.0 grams of an original 200-gram sample of the isotope remains unchanged after 11.46 days?

• 2.87 d

• 3.82 d

• 11.46 d

• 34.38 d

Tags

NGSS.HS-PS1-8

An original sample of the radioisotope fluorine-21 had a mass of 80.0 milligrams. Only 20.0 milligrams of this original sample remain unchanged after 8.32 seconds. What is the half-life of fluorine-21?

• 1.04 s

• 2.08 s

• 4.16 s

• 8.32 s

Tags

NGSS.HS-PS1-8

An original sample of K-40 has a mass of 25.00 grams. After 3.9 x 10^9 years, 3.125 grams of the original sample remains unchanged. What is the half-life of K-40?

• 1.3 x 10⁹ y

• 2.6 x 10⁹ y

• 3.9 x 10⁹ y

• 1.2 x 10¹⁰ y

Tags

NGSS.HS-PS1-8

As the temperature of a sample of a radioactive element decreases, the half-life of the element will

• decrease

• increase

• remain the same

Tags

NGSS.HS-PS1-8