Radioactive Decay

To find the number of molecules, we use Avogadro’s number and the molar mass of nitrogen. - Molar mass of nitrogen is 28 g/mol. - The number of moles in 2.8 g of nitrogen is: - The number of molecules in 1 mole is , so the number of molecules in 0.1 moles is: Thus, the correct answer is .

The half-life equation is given by: Where: - (initial mass) - - (half-life) Substitute the values: Thus, after 600 days, the remaining mass is .