Answer:
¹/₁₆
Step-by-step explanation:
The half-life of Pa-234 (6.69 h) is the time it takes for half the Pa to decay.
After one half-life, half (50 %) of the original amount will remain.
After a second half-life, half of that amount (25 %) will remain, and so on.
We can construct a table as follows:
No. of Fraction
half-lives t/(h) remaining
2 13.38 ¼
3 20.07 ⅛
4 26.76 ¹/₁₆
5 33.45 ¹/₃₂
We see that 26.76 h is four half-lives, and the fraction of Pa-234 remaining
is ¹/₁₆.
