# The isotope chromium-51 has a half-life of 28 days. If the original sample had a mass of 28.0 grams, what mass of the chromium-51 sample remains after 84 days?

##### 1 Answer

May 30, 2016

#### Answer:

#### Explanation:

To find the mass of the chronium-51 sample that remains after

Recall the half-life formula:

#color(blue)(|bar(ul(color(white)(a/a)A=A_0(1/2)^(t/h)color(white)(a/a)|)))# where:

#A=# final amount

#A_0=# initial amount

#t=# time elapsed

#h=# time for half of initial amount to remain after decay (also known as half-life)

Plugging in our known values,

#A=28.0g(1/2)^((84color(white)(i)"days")/(28color(white)(i)"days"))#

#A=color(green)(|bar(ul(color(white)(a/a)color(black)(3.50g)color(white)(a/a)|)))#