Posted by **Gaby** on Tuesday, May 31, 2011 at 9:15pm.

A radium-226 sample initially contains 0.112mol. How much radium-226 is left in the sample after 6400 years. The half-life of radium-226 is 1600 years.

- chemistry -
**DrBob222**, Tuesday, May 31, 2011 at 10:29pm
long way.

k = 0.693/t_{1/2}

ln(No/N) = kt

No = 0.112 mol

N = unknown

k from above.

t = 6400 years.

shorter way.

0.112*(1/2^n)

0.112*(1/2^6400/1600)

0.112*(1/2^4) = N

- chemistry -
**Tanzeel Urooj**, Monday, April 22, 2013 at 3:30am
0.04 is the answer

- chemistry -
**Brandy**, Monday, July 28, 2014 at 4:10pm
The half-life of Radium -226 is 1600 years. How much Ra 226 remains in a 30.0 g sample after 6400 years?

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