Question

manganese-56 has a half life of 2.6 hours how much manganese would have disappeared after 7.8 hours if you started with 20g of manganese

Answer 1

17.5 g of manganese-56

Step-by-step explanation:

Now we have to use the formula;

N/No= (1/2)^t/t1/2

Where

N= mass of manganese-56 left after time (t) = ????

No= initial mass of manganese-56 present = 20 g

t= time taken for N mass of manganese-56 to remain = 7.8 hours

t1/2= half-life of manganese-56 = 2.6 hours

Then we substitute values;

N/20 = (1/2)^7.8/2.6

N/20 = (1/2)^3

N= (1/2)^3 ×20

N= 2.5 g of manganese-56

Mass of manganese-56 that has disappeared after 7.8 hours= 20 -2.5 = 17.5 g of manganese-56