Question

Compute the volume of helium at 1.0 atm and 298 K that will be collected if 2.5 g of 222Rn is stored in a container able to expand to maintain a constant pressure for 15 days. Assume that 222Rn decays to 218Po with a half-life of 3.824 days.

Answer 1

k = 0.693/t_1/2

ln(No/N) = kt
No = 2.5 g
N = solve for this.
k from above.
t = 15 days

Solve for N and subtract from 2.5g to find g Rn decayed. Convert to g He by
g Rn x (atomic mass He/atomic mass Rn) = ?
Then use PV = nRT to solve for V in liters.