Rate constant dependency on reactant concentrations

[Little Etoile]

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Gchem book passage 33 #5:



How is it possible that if rate= k * [A]^x * ^y, k doesn't depend on the concentration of the reactants (i.e. if you manipulate the equation to make it equal to k only, making the reactant concentrations in the denominator)?

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As always, thanks in advance!

 

[sleepy425]

Gchem book passage 33 #5:



How is it possible that if rate= k * [A]^x * ^y, k doesn't depend on the concentration of the reactants (i.e. if you manipulate the equation to make it equal to k only, making the reactant concentrations in the denominator)?



As always, thanks in advance!

well, if x and y are zero, then rate=k

 

[engineeredout]

Gchem book passage 33 #5:



How is it possible that if rate= k * [A]^x * ^y, k doesn't depend on the concentration of the reactants (i.e. if you manipulate the equation to make it equal to k only, making the reactant concentrations in the denominator)?



As always, thanks in advance!

Think about any equation. If you do indeed set k equal to everything else, then while the x and y change, the rate will also change, resulting in the same k.

 

[ecoli]

the rate is essentially asking how long will it take a reaction to reach equilibrium. In this context, the equilibrium constant is dependent on the concentration.

 

[fmaemc2]

How is it possible that if rate= k * [A]^x * ^y, k doesn't depend on the concentration of the reactants (i.e. if you manipulate the equation to make it equal to k only, making the reactant concentrations in the denominator)?

Regarding rates of reaction, recall that the rate of a reaction reflects how quickly it will reach equilibrium. The RATE of a reaction depends on the temperature, and concentration of the reactans, but the value of k, the RATE CONSTANT does not. Were you to re-arrange the equation as you suggest, and were to change the concentration of the reactants, then the RATE of the reaction would change accordingly. Since both numerator and denominator would be affected by a change in the concentration of the reactants to the same degree, the ratio of RATE of reaction over concentration of reactants will stay constant (assuming the same temperature). If this ratio is constant, then the value of k will be constant, and will thus not be dependant upon the concentration of the reactants.

Hope this helps!