rate of consumption sign


Moderators: Chem_Mod, Chem_Admin

Emma Li 2C
Posts: 51
Joined: Fri Sep 29, 2017 7:07 am
Been upvoted: 1 time

rate of consumption sign

Postby Emma Li 2C » Sun Feb 25, 2018 11:43 am

For exercise 15.3 and 15.5, why isn't the rate of reaction of NO2 and the rate of oxygen consumption negative?

Thank you!

Sabrina Dunbar 1I
Posts: 57
Joined: Fri Sep 29, 2017 7:07 am
Been upvoted: 1 time

Re: rate of consumption sign

Postby Sabrina Dunbar 1I » Sun Feb 25, 2018 11:49 am

In 15.3, the entire rate law for the reactant should have a negative sign in front of it. However, because we find the change in concentration as final-initial, 320mmol-450mmol=-130mmol. When fully written out, rate=∆concentration/∆t=-(320mmol-450mmol)/20s=+6.5x10^-3. The negative signs cancel out to generate a positive rate overall.

Angel Ni 2K
Posts: 50
Joined: Sat Jul 22, 2017 3:01 am

Re: rate of consumption sign

Postby Angel Ni 2K » Sun Feb 25, 2018 4:46 pm

The terms themselves imply the sign. If you have a negative rate of consumption, you would be forming the molecule; it doesn't make sense to call it the rate of consumption. The same goes for rate of formation.


Return to “General Rate Laws”

Who is online

Users browsing this forum: No registered users and 3 guests