The first-order decay of radon has a half-life of 3.823 days. How many grams of radon remain after 7.22 days if the sample initially weighs 250.0 grams?

substitute: t 1/2 = ln (2) k →k = ln (2) t 1/2 Into the appropriate equation: [A ]t = [A ]0 ∗ e - kt [A ]t = [A ]0 ∗ e - ln (2) t 1/2 t [A ]t = (250.0 g) ∗ e - ln (2) 3.823 days (7.22 days) = 67.52 g