The half-life of a certain isotope is 1 day. at the end of 3 days, how much of the isotope remains? 1/16 , 1/8, noneof it , 1/3, none above

the half-life of a certain isotope is 30 seconds. how much of a 200 g sample will remain after 2 minutes?
50 , 6.25 , 170, 12.5 , 100

Explanation:

A) The half-life of a certain isotope is 1 day. At the end of 3 days, how much of the isotope remains?

1/16 ,

1/8,

none of it ,

1/3,

none above.

1/8

Explanation:

Given data:

Half life of isotope = 1 day

At the end of day remaining amount = ?

Solution:

Consider that original amount of isotope is 100%.

At time zero = 100%

At one day = 100/2 = 50%

At second day = 50/2 = 25%

At third day = 12.5%

It is the 1/8 of 100.

Multiply the 12.5% × 8 = 100%

It means at the end of 3rd day 1/8 of original amount will remain.

B) The half-life of a certain isotope is 30 seconds. How much of a 200 g sample will remain after 2 minutes?

50 , 6.25 , 170, 12.5 , 100

12.5 g

Explanation:

Given data:

Half life = 30 sec

Total amount = 200 g

Amount after 2 min (120 sec)  = ?

Solution:

Half lives  = T elapsed / half life

Half lives  = 120 sec/ 30 sec

Half lives  = 4

At time zero = 200 g

At first half life = 200 g /2 = 100 g

At second half life = 100 g/2 = 50 g

At third half life = 50 g/2 = 25 g

At 4th half life = 25 g/2 = 12.5 g

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