Answer:
2.50 h
Step-by-step explanation:
The half-life of a sample is the time it takes for half of it 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 Mass
half-lives remaining Remaining/g
1 ½ 80
2 ¼ 40
3 ⅛ 20
4 ¹/₁₆ 10
5 ¹/₃₂ 5.0
6 ¹/₆₄ 2.5
We see that 5.0 g remain after five half-lives.
5t_½ = 12.5 h Divide each side by 5
t_½ = 2.50 h
The half-life is 2.50 h.