The mass decay rate is of the form

where
m₀ = 3000 g,the initial mass
k = the decay constant
t = time, years.
Because the half-life is 30 years, therefore

After 60 years, the mass remaining is

Answer: 750 g
First convert 0.163 grams of N2O to mol by dividing it with
the molecular weight. The molecular weight of N2O is 44 grams/mol. The answer
would be 3,79x10^-3. Then multiply it with 2 since there are 2 Nitrogen in one
mole of N2O. Therefore, there are 7.41x10^-3 moles of Nitrogen.
If it is already balanced because the compounds aluminum(Al) and oxygen(O) have the same number of atoms