chemical kinetics set 2

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1. 2 NO (g) + O2 (g) ---> 2 NO2 (g)

how do we get the instantaneous rate at t=2000s ?
• 1) we use a graph of conc. vs. time
• 2) we find 2000 s and mark it
• 3) draw a tangent line
• 4) pick 2 points on the tangent line
• 5) derive a slope equation such that, for example: Δ[reactant] / Δ t
2. For the reaction, 2 NO (g) + O2 (g) ---> 2 NO2 (g):

which species can dictate the rate of the reaction?

How can we convert 1 species rate to another species rate?
the rate of a rxn is based on the species that has a coefficient of one.

• Say we have NO's instantaneous rate of consumption to be -1.2 x 10-6 M/s.
• We cannot use NO bc its coefficient is 2.  We can it convert though, to O2's rate.

For example, if we have an instantaneous rate (t = 2000s) of NO (consumption), we can translate that to O2's rate:

instantaneous rate of consumption of O2 = - (Δ[NO] / Δt) = - (-1.2 x 10-6 M/s) = 6.0 x 10-7 M/s
3. 2 CO (g) + 2 NO (g) ---> N2 (g) + 2 CO2 (g)

equate the rate of each species in this rxn
rate = (Δ[N2] / Δt) = (Δ[CO2] / Δt) = - (Δ[CO] / Δt) = - (Δ[NO] / Δt)
4. 2 CO (g) + 2 NO (g) ---> N2 (g) + 2 CO2 (g)

Compare the rate of formation of N2 with the rate of consumption of CO
(Δ[N2] / Δt) = - (Δ[CO] / Δ t)

The rate of formation of N2 is one half the rate of consumption of CO
5. 2 CO (g) + 2 NO (g) ---> N2 (g) + 2 CO2 (g)

Compare the rate of formation of CO2 with the rate of consumption of NO
(Δ[CO2] / Δt) = - (Δ[NO] / Δt)

The rate of formation of CO2 is the same as the rate of consumption of NO
6. N2O5 ---> NO2 + NO3

With the help of a table or graph that indicates conc. of N2O5 vs. time, how can we get the average rate of consumption of N2O5?
for the average rate of N2O5 consumption:

Δ[N2O5] / Δt

*for Δt, use a specific time interval (for avg. rate)

For example:

average rate = (Δ[N2O5]final - Δ[N2O5]inital) / (tfinal - tinital)

this will give us the rate for the rxn (for the time interval stated) also because the coefficient for N2Ois one.
 Author: ryansamona ID: 195798 Card Set: chemical kinetics set 2 Updated: 2013-01-28 00:43:36 Tags: chemistry Folders: Description: kinetics Show Answers: