## rate of reaction formula

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

shaunajava2e
Posts: 66
Joined: Fri Sep 28, 2018 12:26 am

### rate of reaction formula

the solution manual shows that the equation for rate of reaction is: - (deltaConcentration) / (deltaTime).
Why is there a negative in the equation/formula??

This is the problem im referring to:
15.3 6th ed.
In 20. s, the concentration of nitrogen dioxide, NO2, decreases from 450 mmol/L to 320 mmol/L in the reaction 2 NO2(g) 2 NO(g) O2(g). (a) Determine the rate of reaction of NO2. (b) Determine the rate of formation of O2.
(c) What is the unique rate of the reaction?

Elaine Pham 2E
Posts: 58
Joined: Fri Sep 28, 2018 12:28 am
Been upvoted: 1 time

### Re: rate of reaction formula

I believe there is a negative sign because they are asking for the rate of the overall reaction of NO2, which needs to be positive so they add the negative sign to make the value become positive. If they were asking for the rate of consumption of NO2, I think there would not be a negative sign in front because rate of consumption is decreasing.