Posted by **Derren** on Saturday, February 18, 2012 at 11:47pm.

The initial concentration of the a substance was 1.95 M. After 27.72 hours the concentration was 0.9750 M. After anothers 55.44 hours the concentration was 0.4875 M (total time = 83.16 hours).

If another experiment were conducted in which the initial concentration was 0.427 M, how long would it take for the substance to reach a concentration 0.0213 M?

- chemistry -
**DrBob222**, Sunday, February 19, 2012 at 12:13am
You use 1st order equation of

ln(No/N) = kt and solve for k.

Use the second time period to calculate k again. If k is the same, then this is a first order reaction and you can use that equation on the other experiment. If k is not the same; you assume it is a second order equation and try that for both sets to see if k really is k. If it is then you can use second order equation for the other experiment.

Second order equation is

(1/A) - (1/Ao) = akt.

Post your work if you get stuck.

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