Rate Law

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

Ryan Fang 1D
Posts: 53
Joined: Sat Jul 22, 2017 3:00 am

Rate Law

Why is the rate law for reactants negative?

Sean Monji 2B
Posts: 66
Joined: Fri Sep 29, 2017 7:06 am

Re: Rate Law

The rate law shows how the concentration of the reactants are changing over time. If the reactants are being consumed to form products, then the reactants must be decreasing. Therefore, the rate at which the concentration of reactants are changing over time must be negative.

Rachel Formaker 1E
Posts: 86
Joined: Fri Sep 29, 2017 7:04 am
Been upvoted: 2 times

Re: Rate Law

Rates are always given as positive values.

Since the equation for rate is rate= d[]/dt
and the concentration of reactants is decreasing, simply using the above equation for the rate of consumption of reactants would yield a negative rate.

To correct this and give a positive rate for rate of consumption, we use
rate = - d[reactants]/dt

204918982
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

Re: Rate Law

The concentration of reactants is negative so there needs to be a negative sign to cancel it out and make the rate positive

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