Answer:
[tex]\huge\boxed{\sf 5 \ mL}[/tex]
Step-by-step explanation:
Amount of Br-82 = 80 mL
Half-life = 35 hours
Total time = 140 hours
No. of half lives spent:
= Total time / Half-life
= 140 / 35
= 4 half lives
After 1st half life:
= 80 / 2
= 40 mL
After 2nd half life:
= 40 / 2
= 20 mL
After 3rd half life:
= 20 / 2
= 10 mL
After 4th half life:
= 10 / 2
= 5 mL
[tex]\rule[225]{225}{2}[/tex]
