Question

Starting with 100 grams of uranium-238, after one half life has gone by, how many grams of uranium-238 will remain?

A._12.5 grams
B._25 grams
C._50 grams
D._100 grams

Answer 1

Answer C, 50 grams.
This is because a half life is the time it takes for a sample of an unstable isotope to spontaneously so that half of the original sample remains

Answer 2

Answer : The correct option is, (C) 50 grams

Solution :

Formula used :

`a=(a_o)/(2^n)`

where,

a = amount of reactant left after n-half lives = ?

`a_o` = Initial amount of the reactant = 100 g

n = number of half lives = 1

Putting values in above equation, we get:

`a=(100)/(2^1)`

`a=50g`

Therefore, the amount of uranium-238 remain will be, 50 g