# chemistry

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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 -

long way.
k = 0.693/t1/2
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 -

• chemistry -

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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