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### 15.3 C

Posted: Wed Feb 28, 2018 12:19 pm
In 20 s, the concentration of nitrogen dioxide, NO2, decreases from 450 mmol/L to 320 mmol/L in the reaction 2NO2(g) --> 2NO(g) + O2(g).
(c) What is the unique rate of the reaction?

How do you find the unique rate of the reaction? I don't really get what the solutions manual says about this part.

### Re: 15.3 C

Posted: Wed Feb 28, 2018 1:01 pm
The unique rate of the reaction is always given by this format (click on the link to see)
https://i.ytimg.com/vi/ycXCSY7N3qc/maxresdefault.jpg

So therefore, according to this equation, because NO2 has a coefficient, it's rate of consumption it must be divided by that coefficient to find the rate of the reaction.

### Re: 15.3 C

Posted: Wed Feb 28, 2018 3:39 pm
When you calculate the change in concentration over the change in time, you get the rate of 2NO2, but you need the unique rate. This means that they're asking for the rate of one mole of NO2, so you divide the rate by 2.

### Re: 15.3 C

Posted: Wed Feb 28, 2018 4:16 pm
The unique reaction rate takes into account the coefficients of the chemical equation.

### Re: 15.3 C

Posted: Wed Feb 28, 2018 6:07 pm
The solution manual lists instead of an answer for (c), another answer for (b). And it's solution is +3.3 x 10^-3 instead of -3.3 x 10^-3. Is this another error? Or could someone explain to me why this solution would be positive and not negative, if the formula for unique rate would be -1/a ΔA/Δt.

### Re: 15.3 C

Posted: Wed Feb 28, 2018 9:04 pm
it's a positive value for b) because when you're finding the rate of the products (formation of O2), it's + 1/c ΔC/Δt.

### Re: 15.3 C

Posted: Thu Mar 01, 2018 8:06 am
The unique rate of a reaction takes into account the stoichiometric coefficients of a reaction. It is the rate of appearance/disappearance of any species in a reaction divided by its stoichiometric coefficient.

### Re: 15.3 C

Posted: Thu Mar 01, 2018 12:16 pm
the rate you find for 2NO2 would be the unique rate multiplied by two because there is 2 moles of NO2 so to find the unique rate you would just divide by 2

### Re: 15.3 C

Posted: Sat Mar 03, 2018 12:44 pm
All you have to do to change and correct your answer if find the rate PER mole