+0  
 
0
629
7
avatar+2496 

A radioactive isotope has a half-life of 50 years. its mass in 1980 was 800 grams. What will its mass be in the year 2020 ?

 Dec 12, 2015

Best Answer 

 #6
avatar
+10

Since the half-life=50 years, therefore,

40/50=.8 half-lives, then we have,

800 X 2^-.8=459.479...grams left after 40 years.

 Dec 12, 2015
 #1
avatar+9924 
+10


There are still 459,48 grams.

laugh

 Dec 12, 2015
 #2
avatar+2496 
+5

Thanks Omi67 ! :)

 Dec 12, 2015
 #3
avatar
+5

This is confusing me.... Does this solution assume that the ENTIRE mass is radioactive???  Then,   I THINK there will be 459.48 gms of RADIOACTIVE material left, but the mass of the SAMPLE will be greater as some atoms that are no longer radioactive will remain...right?

 Dec 12, 2015
edited by Guest  Dec 12, 2015
edited by Guest  Dec 12, 2015
 #4
avatar+2496 
+5

Omi how didi you get 0.5

 Dec 12, 2015
 #5
avatar+2496 
+5

aa i understood )

 Dec 12, 2015
 #6
avatar
+10
Best Answer

Since the half-life=50 years, therefore,

40/50=.8 half-lives, then we have,

800 X 2^-.8=459.479...grams left after 40 years.

Guest Dec 12, 2015
 #7
avatar+9924 
+10

The graph

laugh

 Dec 12, 2015

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