How much nitrogen-13 would be left after 40 minutes if the sample started at 4g

0.248 g

Explanation:

We are given;

Time as 40 minutes Original amount of N-13

We are required to calculate the amount left after decay.

We need to know the half life of N-13 first; Half life of N-13 is 9 minutes 58 seconds (9.965 minutes0

We are going to use the formula;

Remaining amount = Original amount * 0.5^n

That is; N = N₀ * 0.5^n, where n is the number of half lives.

n = 40 minutes : 9.965 minutes

= 4.014

Therefore;

N = 4 g * 0.5^4.014

= 0.248 g

Therefore, the mass of Nitrogen-13 that will be left is 0.248 g