The half-life of sodium-22 is 2.6 years. A sample contains 800 mg of this isotope.

Which expression represents the mass of sodium remaining after h half-lives?

S = 0.5 (800) h

S = 800 (0.5) h

S = 8000.5h

S = 800h + 0.5

Which expression relates h, the number of half-lives, and y, the number of years?

The answer is B S=800 (0.5) h

Which expression relates h, the number of half-lives, and y, the number of years? Answer h=y/2.6

Combine the first two equations and laws of exponents to find the equation for the mass of sodium remaining after y years. Answer S=800 (0.766) y

Approximately how many milligrams of sodium remain after 8.4 years? Answer 85.2 mg