A chemical substance has a half life of 5 years. A chemist currently has 2000 grams of the substance. If the substance remains untouched, after 25 years, how much of the substance will be left?

1 Answer
Apr 29, 2017

Answer:

after 25 years there would be #62.5# grams of the substance

Explanation:

Half life refers to the time it takes or half of the substance to decay.

If the half life is 5 years and we begin with 2000 grams, we can create a data list of the decay.

0 years = 2000 grams

5 years = 1000 grams

10 years = 500 grams

15 years = 250 grams

20 years = 125 grams

25 years = 62.5 grams

You can also use the formula

#A_f = A_i (1/2)^(t/h)#

#A_f =# Final Amount
#A_i =# Initial Amount
#t =# time
#h=# half-life

#A_f = 2000(1/2)^(25/5)#

#A_f = 2000(1/2)^5#

#A_f = 2000(1/32)#

#A_f = 62.5#