Posted by **Dena** on Tuesday, November 10, 2009 at 1:36pm.

I've tried this problem over and over again, but im not getting the right answers! This is the problem.......

Dinitrogen pentoxide, N2O5, decomposes when heated in carbon tetrachloride solvent.

N2O5 2 NO2 + 1/2 O2(g)

If the rate constant for the decomposition of N2O5 is 6.2 10-4/min, what is the half-life(in Minutes)? (The rate law is first order in N2O5.)

How long would it take for the concentration of N2O5 to decrease to 6.250% of its initial value(in minutes)?

How long would it take to reach 0.8% of its initial value(in minutes)?

Can anyone help me? Thank You!!!

- Chemistry -
**DrBob222**, Tuesday, November 10, 2009 at 1:38pm
You've tried it over and over? Show us your work. And what is the correct answer?

- Chemistry -
**Dena**, Tuesday, November 10, 2009 at 1:44pm
I don't know the correct answer thats what i have to find.

for the first part here is my work.....

6.2e-4/min=0.0372seconds

half life: t_1/2=0.693/0.372s

=18.6sec*1min/60sec=0.310min (which is not right!)

- Chemistry -
**DrBob222**, Tuesday, November 10, 2009 at 2:06pm
Since the problem asks for the half-life in minutes, I wonder why you converted to seconds then back to minutes? Have you tried leaving the rate in min?

t(1/2) = 0.693/6.2 x 10^-4 = ??

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