+0

# little and evil question ! :)

0
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+2493

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 ?

Solveit  Dec 12, 2015

#6
+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.

Guest Dec 12, 2015
Sort:

#1
+8826
+10

There are still 459,48 grams.

Omi67  Dec 12, 2015
#2
+2493
+5

Thanks Omi67 ! :)

Solveit  Dec 12, 2015
#3
+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?

Guest Dec 12, 2015
edited by Guest  Dec 12, 2015
edited by Guest  Dec 12, 2015
#4
+2493
+5

Omi how didi you get 0.5

Solveit  Dec 12, 2015
#5
+2493
+5

aa i understood )

Solveit  Dec 12, 2015
#6
+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.

Guest Dec 12, 2015
#7
+8826
+10

The graph

Omi67  Dec 12, 2015

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