The half-life of Pa-234 is 6.75 hours. If a sample of Pa-234 contains 112.0 g, 1 point
how much will remain after 13.5 hours? *
O 1129
O 569
O 289
O 149

28g remain after 13.5 hours

Explanation:

Element decayment follows first order kinetics law:

ln[Pa-234] = -kt + ln [Pa-234]₀ (1)

Where [Pa-234] is concentration after t time, k is rate constant in time, and [Pa-234]₀ is initial concentration

Half-life formula is:

6.75 = ln2 / k

k = 0.1027hours⁻¹

Using rate constant in (1):

ln[Pa-234] = -0.1027hours⁻¹×13.5hours + ln [112.0g]

ln[Pa-234] = 3.332

[Pa-234] = 28g after 13.5 hours

it means there are 3 atoms of oxygen

it is the most commonly accepted one