question about rate law

[flyingwarthog]

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When we talk about rate laws in gen chem, the rate itself has the units M/s. Here is where I am confused about these units: molarity of what?

If the rate is 10 M/s for a reaction, then the molarity of what is changing 10 M per second? Does this relate to the stochimetric coefficients in the chemical equation? Like if a reactant had a stochimetric coefficient of 1 then its molarity would decrease 10 M/s? Of another reactant had a stochimetric coefficient of 2, would its molarity decrease at 20 M/s?

 

[TheRhymenocerous]

It depends how you've defined the rate – it could be the decrease in concentration of a reactant or the increase in concentration of a product. But yeah, it is related to coefficients. If two reactants have the same coefficient, they have the same rate. If a reactant and a product have the same coefficient, they have the same rate but opposite signs. If you know all the coefficients, you can get the rate for each compound by knowing one.

 

[flyingwarthog]

It depends how you've defined the rate – it could be the decrease in concentration of a reactant or the increase in concentration of a product. But yeah, it is related to coefficients. If two reactants have the same coefficient, they have the same rate. If a reactant and a product have the same coefficient, they have the same rate but opposite signs. If you know all the coefficients, you can get the rate for each compound by knowing one.

Thanks for the answer!