Homework Help: chemistry

Posted by Trixie on Friday, April 16, 2010 at 5:04pm.

A radioactive sample contains 3.25 1018 atoms of a nuclide that decays at a rate of 3.4 1013 disintegrations per 26 min.
(a) What percentage of the nuclide will have decayed after 159 d?
%

(b) How many atoms of the nuclide will remain in the sample?
atoms

(c) What is the half-life of the nuclide?
days

I have a general idea of how to solve this but keep getting the incorrect answer...I've tried a few different ways so I'm not sure where I'm going wrong. My initial attempt was to convert days into minutes for my calculations. I used the equation N'=Ne^-kt where I calculated k to be the rate given (over minutes). I don't need the answers per se...I think once I know how to correctly approach this I should be fine in figuring them out...Thanks

chemistry - Trixie, Friday, April 16, 2010 at 5:08pm
Oh and when I try to put this into my calculator I get 0... sorry if I am not catching on fast enough for some....I worked graveyard last night and Haven't slept in over 35 hours...
chemistry - Trixie, Friday, April 16, 2010 at 5:18pm
Another attempt I made gave me relatively "reasonable" answers...but still doing something wrong.

I converted the minutes to days and used that in the rate to find k via k= rate/N ; N being 3.25E18 atoms. this calculated k to be .00145.

I plugged this into N'=Ne^-kt....can someone please point out what I am doing wrong?
chemistry - DrBob222, Friday, April 16, 2010 at 5:36pm
My recommendation is
a. go to bed for some rest.
b. take fewer classes next quarter/semester/year.
chemistry - Trixie, Friday, April 16, 2010 at 6:27pm
Sleep is a bit of a luxury.....unfortunately I'm one of those students that doesn't have an option of taking a lighter load or working less....luckily I graduate in a few weeks. In the meantime I need to finish these problems so that I can go to bed....but they are due at 11pm tonight and if I go to sleep before completing them I know I won't wake up.
chemistry - Trixie, Friday, April 16, 2010 at 6:30pm
Could you please just explain what I am doing wrong so that I can know how to approach these problems? I appreciate the advice and am well aware I need to go to bed...but I have to get these finished and my professor is out of town attending a memorial service and unable to answer emails until Sunday...

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