The halflife of a substance is the time it takes for half of

The half-life of a substance is the time it takes for half of the substance to remain after natural decay. Radioactive water (tritium)has a half-life of 12.6 years. About how long will it take for 48 grams of decay to 1.5 gram?

Solution

decay constant =0.693/half life = 0.693/12.6 =0.055

N= Noe^-kt

N= 48e^(-0.055t)

N = 1.5 gms find t :

1.5 = 48e^(-0.055t)

ln(1.5/48) = - 0.055t

t = 63 years