Question

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

Answer 1

Answer:

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.