the half life of carbon 14 is 5730 years. How many grams of parent material will remain from a 100 gram sample of carbon 14 after 2 half lives

Question

anonymous · Answer

$$N=N_0 e^{-kt}$$
where 
n0 = starting mass
n = mass after t years
k = rate
t = years

is this formula right?

anonymous · Answer

yes :)

anonymous · Answer

if it is, then plug the values for half life to find the rate

$$\huge 1 = 2e^{-k5730}$$
find k then substitute it in the formula with t = half life time x 2 (5730 x 2) and n0 = 100

anonymous · Answer

do you get it?

anonymous · Answer

kinda?

anonymous · Answer

k = 0.000120968

$$\huge N  = 100e^{0.000120968 \times 11460}$$~

lgbasallote · Answer

are you sure about this @nphuongsun93 ?

anonymous · Answer

Hope it's OK to butt in here.  Since the problem gives an integral number of half-life(s), the problem is a lot easier.  The amount remaining after 2 of them is just 1/2 times 1/2 = 1/4.

anonymous · Answer

yea... actually not too sure now D:
after two half life would just equal 1/4 of the original mass.

anonymous · Answer

oh nvm my way got the same answer anyway l0l

anonymous · Answer

Also, given the half-life, the rate k times the half life T = ln 2

anonymous · Answer

OK.  Good.