Why Is My Calculation of the Initial Rate of Decomposition for NO2 Not Accepted?

AI Thread Summary
The discussion centers on calculating the initial rate of decomposition for the reaction 2NO2 → 2NO + O2, using a rate constant (k) of 0.54 and an initial concentration of 0.008 M. The user initially calculated the rate as 0.000035 M/s but faced issues with acceptance of this answer. Clarification revealed that the rate constant was indeed 0.54, and confusion arose from a previous question regarding the instantaneous rate at a different concentration, which was accepted but required rounding. The user speculates whether the problem's phrasing regarding the rate of decomposition might be misleading, particularly given the second-order nature of the reaction. Understanding the nuances of rate calculations in relation to the reaction order is essential for accurate results.
chhhnhhsh
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Homework Statement


What is the Initial Rate of Decomposition for NO2.
Where 2NO2-----> 2NO + O2
K=.54
Concentration at t=0 is .008 M
This is a second order reaction.

Homework Equations


Rate=k[C]2

The Attempt at a Solution


Rate=.54[.008]2=.000035 (directed to give a two sig fig answer)

This answer is not being accepted, I'm not sure what I'm missing?
 
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welcome to pf!

hi chhhnhhsh! welcome to pf! :smile:

isn't it 5.4, not .54 ? :redface:
 
Thank you for the welcome!
Sorry I misprinted the information above.
A previous question for this problem was "what is the value of the rate constant" and the text calculates it for you as k=(.54 / M*s).

What is really getting to me is a previous question as well where it asked for the instantaneous rate at t=100 where the concentration = .00559 M.

To calculate this I did the same thing.
rate=.54(.00559)2 = .000017 M/s. The program accepted this answer but said I should have rounded to .000018 M/s. Which I didn't understand because the real answer is .000016874.
Should I be using a different rate calculation?
 
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Maybe it's a bit of a trick question based oon the fact that the rate constant is a 2nd order one for bimolecular reaction 2NO2 -> ..., but they ask for "rate of decomposition of NO"2. ?
 
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