The radioactive element strontium-90 has a half-life of 28 years. suppose we start with a 50-g mass of strontium-90. how much will be left after 174 years? compute the answer to three significant digits.

7.71 grams

Explanation:

Half-life of strontium-90 = 28 years

First we have to calculate the rate constant, we use the formula :

Now we have to calculate the age of the sample:

Expression for rate law for first order kinetics is given by:

where,

k = rate constant  =

t = age of sample  = 174 years

a = initial amount of the reactant  = 50 g

a - x = amount left after decay process  = ?

Now put all the given values in above equation, we get

Thus amount left after 174 years is 7.71 grams.