Posted by **Anonymous** on Saturday, November 5, 2011 at 6:18pm.

What percent of the original sample of strontium-90 (half-life = 28.9 years) will remain after the following time periods?after 18 years?

after 47.5 years?

after 1008 years?

- chemistry -
**DrBob222**, Saturday, November 5, 2011 at 6:42pm
k = 0.693/t_{1/2}

ln(No/N) = kt

Substitute into equation 1 and solve for k, the substitute into equation 2 and solve for N. No will be 18, 47.5, 1008 years.

- chemistry -
**Anonymous**, Saturday, November 5, 2011 at 7:48pm
.....it's actually asking for the % left after so many years

- chemistry -
**DrBob222**, Saturday, November 5, 2011 at 8:02pm
So N = amount left.

% = (N/No)*100 = ?

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