Answer:
12.5 grams
Explanation:
From the question,
E' = E/2⁽ⁿ/a⁾....................... Equation 1
Where E' = mass left, E = Original mass, n = time, a = half-life.
Given: E = 200 grams, n = 40 years, a = 10 years.
Substitute these values into equation 1
E' = 200/2⁽40/10⁾
E' = 200/2⁴
E' = 200/16
E' = 12.5 grams.
Hence 12.5 grams of the isotope will be left.
