Iodine-131 decays to form xenon-131. the half-life of this reaction is 8.07 days. from a 200-g sample of iodine-131, how much of the sample is xenon-131 after 16.14 days?

Answer : The amount of the sample left is, 50.25 grams

Solution : Given,

As we know that the radioactive decays follow first order kinetics.

First we have to calculate the rate constant of a radioisotope.

Formula used :

The expression for rate law for first order kinetics is given by :

where,

k = rate constant  =

t = time taken for decay process  = 16.14 days

a = initial amount of the reactant  = 200 g

a - x = amount left after decay process  = ?

Putting values in above equation, we get the value of amount left.

Therefore, the amount of the sample left is, 50.25 grams

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.