Question

In 5.49 seconds, 1.20 g of argon-35 decays to leave only .15 g. What is the half life of argon-35?

Answer 1

1.83 sec

Explanation:

`m_i=m_r*2^n`

`m_i " is the initial mass present of the radioisotope."`

`m_r" is the mass remaining after a certain time "`

`n " is the number of periods," = (time)/T" where T is the half-life."`

`m_i=m_r*2^n`

`m_i/m_r=2^n`

`2^n=(1.20\ g)/(0.15\ g)`

`2^n=8`

`2^n=2^3`

`" "color(red)ulbar(color(black)(n=3))`

`n= (time)/T"`

`T "(half-life)"= (time)/n`

`T = (5.49 sec)/3`

`color(blue)(ulbar(color(red)(T = 1.83" sec"))`