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April 17, 2014

April 17, 2014

Posted by **Anonymous** on Sunday, February 28, 2010 at 2:17pm.

If a sample of C-14 initially contains 1.1 mmol of C-14 , how many millimoles will be left after 2275 years?

- chemistry -
**DrBob222**, Sunday, February 28, 2010 at 2:48pmBoth problems are similar. Use this first equation to evaluate k.

k = 0.693/t_{1/2}

Then substitute k into this equation.

ln(No/N) = kt

To make thing easy I would assume we start with 100 atoms so No = 100. If 25% of the atoms decay, that will leave 75 atoms remaining; therefore, N = 75. You know k from the first equation, you can solve for time.

Second problem is done the same way but you solve for N.

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