Posted by **csb** on Wednesday, October 6, 2010 at 10:27am.

A reaction is first order and it takes 324 minutes for the reaction to be 50.0% complete. How long will it take for the reaction to be 85.0% complete at the same temperature? The answer is 887 minutes but I have no idea how he got that? help

- chemistry -
**DrBob222**, Wednesday, October 6, 2010 at 4:23pm
ln(No/N) = kt

For convenience, start with 100 for No.

ln(100/50) = k(324)

solve for k, the rate constant.

Second part.

ln(100/15) = k(from above)t

Solve for t.

I get 886.8 which rounds to 887 minutes.

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