Element X had a mass of 300g and a 1/2 life of 10 years. how many grams will remain after 40 years?

18.75 grams

Explanation: Half-life refers to the time taken by a radioactive material to decay by half of the original mass. In this case, the half-life of element X is 10 years, which means it takes 10 years for a given mass of the element to decay by half of its original mass. To calculate the amount that remained after decay we use;

Remaining mass = Original mass * (1/2) ^n, where n is the number of half-lives

Number of half-lives = Time for the decay : Half-life

= 40 years : 10 years

= 4

Therefore;

Remaining mass = 300 g * (1/2) ⁴

= 300 g * 1/16

= 18.75 g

Hence, a mass of 300 g of an element X decays to 18.75 g after 40 years.