Question 18.1: The half-life of 53^131I is 8 days. How much 53^131I from a...

Using the following graph, we can find the number of grams of ^{131}I remaining after one half-life:

Trace a perpendicular line from 8 days on the x-axis to the line on the graph. Now trace a horizontal line from this point on the plotted line to the y-axis and read the corresponding grams of ^{131}I Continue this process for each half-life, adding 8 days to the previous value on the x-axis:

Half-lives                          0        1           2          3           4          5
Number of days                         8         16        24         32        40
Amount remaining      32g     16g       8g       4 g         2 g       1 g
Starting with 32 g, one gram of^{131}I  remains after five half-lives (40 days).