Negative 1/a

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

Jack Papciak 2F
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Negative 1/a

Why is there a "-" in -1/a in the differential rate law?

Tatiana Hage 2E
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Re: Negative 1/a

There is a negative sign because the concentration of the reactant decreases during the reaction.

Nicole 1F
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Re: Negative 1/a

In addition, the rate needs to be positive in the end.

Nisarg Shah 1C
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Re: Negative 1/a

Because the reactant is being consumed, the overall concentration of the reactant is decreasing so there is a negative rate of change. However, if the question asked at what rate was A being consumed, then it will be a positive answer. Just be careful about how the question is worded!

Rachel Lu_dis1H
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Re: Negative 1/a

Since products is decreasing, the slope will be negative when you take the tangent to the curve. (that means that the slope of the products is positive because products is increasing)

Cristina Sarmiento 1E
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Re: Negative 1/a

Nisarg Shah 1C wrote:Because the reactant is being consumed, the overall concentration of the reactant is decreasing so there is a negative rate of change. However, if the question asked at what rate was A being consumed, then it will be a positive answer. Just be careful about how the question is worded!

Can you please further explain as to why the rate would be a positive answer if the question was worded differently?

Nisarg Shah 1C
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Joined: Sat Jul 22, 2017 3:00 am

Re: Negative 1/a

For example, if the question asked "what is the rate of decomposition of reactant A" the rate would be positive, even though the concentration of A is decreasing.

Michael Downs 1L
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Re: Negative 1/a

Cristina Sarmiento 1E wrote:
Nisarg Shah 1C wrote:Because the reactant is being consumed, the overall concentration of the reactant is decreasing so there is a negative rate of change. However, if the question asked at what rate was A being consumed, then it will be a positive answer. Just be careful about how the question is worded!

Can you please further explain as to why the rate would be a positive answer if the question was worded differently?

Since the word consumed is being used, then the negative rate of change is already being implied so the answer shouldn't have another negative.

Mitch Walters
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Joined: Fri Sep 29, 2017 7:07 am

Re: Negative 1/a

Concentration of reactants decreases.