[katyi6]

Hey everyone I was wondering if I could get a little help on a question, it would be much appreciated!

The radioactive decay of tritium (^3H) follows first order kinetics with a half life of 12.3 years. If a 10mg sample of hydrogen contanins 2.2 mg of tritium, how much tritium would remain after 6.15 years?

The answer is supposed to be 1.6 mg.
I'm having trouble actually approaching the problem, since its first order I used the information for tritium in the t1/2= ln2/k formula and then use k in the ln[At]=-akt + ln[A0] where a=1, k=0.480 t=6.15 and [A0]=2.2 mg.

I've tried doing that but I dont get the right answer. Any help would be much appreciated, thank you

[rabolisk]

Most likely a math error. Your rate constant k is not correct, but your approach is fine.

[DevaDevil]

I'm having trouble actually approaching the problem, since its first order I used the information for tritium in the t1/2= ln2/k formula ... where k=0.480

ln (2) / 12.3 y = 0.5635 y^-1, maybe there is your problem?

A = A₀ * e^-kt => I then get

A = 1.56 = 1.6 (in 2 significant)

[katyi6]

I'm having trouble actually approaching the problem, since its first order I used the information for tritium in the t1/2= ln2/k formula ... where k=0.480

ln (2) / 12.3 y = 0.5635 y^-1, maybe there is your problem?

A = A₀ * e^-kt => I then get

A = 1.56 = 1.6 (in 2 significant)

Oh wow I am an idiot, I derived the half life formula wrong, thank you so much