Guys,

Can some1 please explain me how in the world they got the answer to be 8 hours....( i hate half-life kinda qns) anybody have trick to this kind of problems or better off...easier to understand so that one can do this kind of problems....(radioactive decay problems)

thanks

Guys,

Can some1 please explain me how in the world they got the answer to be 8 hours....( i hate half-life kinda qns) anybody have trick to this kind of problems or better off...easier to understand so that one can do this kind of problems....(radioactive decay problems)

thanks

Post the question please. Not everyone has destroyer, I would be happy to help if I can.

Sorry...here you go

Consider radioactive nuclide X. If 88% of a pure sample decays in 24 hours, what is the half-life?

a) 3 hrs
b) 8 hrs
c) 14 hrs
d) 16 hrs
e) 4 hrs


Thanks a ton!!!

Well you can pick each answer see how well it fits. For example, starting with half life of 3 hrs, after 3 hrs 50% decay, after 6 hours 75% decay, after 9 hours 87.5% decay, so that cant be right. Now 8 hour half life: after 8 hrs 50%, after 16 hrs 75%, after 24 hrs 87.5%. So 8 hours is right, no need to continue.

Ok I wasn't seeing this but this is the way I got it:
U know the 1st half life of a radioactive compound is 50%, once u get to the 2nd half life it would be 25%, and the 3rd would be 12.5% once u add the %'s u get about 88% so if by the 3rd half life u get 88% in 24 hrs. That means that every half life is 8hrs (8hrs * 3 half lives = 24 hrs)
Hope it helped. =)

Well you can pick each answer see how well it fits. For example, starting with half life of 3 hrs, after 3 hrs 50% decay, after 6 hours 75% decay, after 9 hours 87.5% decay, so that cant be right. Now 8 hour half life: after 8 hrs 50%, after 16 hrs 75%, after 24 hrs 87.5%. So 8 hours is right, no need to continue.

I agree, this process doesn't require you use too much brainpower.

if you know the concept it will be much easier nd faster. lets start together if we ha ve 100 percent pure starting material half life means the period of the time the half of sample will decay:
100-88= 12% remaining for sample
(these percenatge is for remaining sample)

100% --------> 50%-------->25%---------> 12.5%
that means after 3 period half time, 12.5% will remain:

24/3=8
(the question would change to more accurate form 87.5%)
rember the ramaining samples, based on percentage ( each arrow is one half time period)
100------->50------->25------->12.5--------->6.25

if you know the concept it will be much easier nd faster. lets start together if we ha ve 100 percent pure starting material half life means the period of the time the half of sample will decay:
100-88= 12% remaining for sample
(these percenatge is for remaining sample)

100% --------> 50%-------->25%---------> 12.5%
that means after 3 period half time, 12.5% will remain:

24/3=8
(the question would change to more accurate form 87.5%)
rember the ramaining samples, based on percentage ( each arrow is one half time period)
100------->50------->25------->12.5--------->6.25

I'm pretty sure we have at least a couple correct explanations, no need to explain it exactly as it already has been.

I'm pretty sure we have at least a couple correct explanations, no need to explain it exactly as it already has been.

you are right, I didn't pay attention to your explanation. it was too late. :)