Rate constant

ApexT

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Hey guys,

Just looking for some help with his question:

The concentration of a reactant halves every 20 minutes. What are the units of the rate constant for this reaction?

Am I right in saying that this would be a first order reaction because the reactant has a steady half life? From this the rate constant would then be S^-1. How would this differ from a second order reaction?

Thanks

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charco

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(Original post by ApexT)
Hey guys,

Just looking for some help with his question:

The concentration of a reactant halves every 20 minutes. What are the units of the rate constant for this reaction?

Am I right in saying that this would be a first order reaction because the reactant has a steady half life? From this the rate constant would then be S^-1. How would this differ from a second order reaction?

Thanks

Yes, 1st order reaction = constant half life.

What do you mean "how does this differ from 2nd order?"

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JacobAlevels

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(Original post by ApexT)
Hey guys,

Just looking for some help with his question:

The concentration of a reactant halves every 20 minutes. What are the units of the rate constant for this reaction?

Am I right in saying that this would be a first order reaction because the reactant has a steady half life? From this the rate constant would then be S^-1. How would this differ from a second order reaction?

Thanks

Yep it's a 1st order reaction. The equation for the rate would be rate=k[A] with A being the reactant whose conc halves, so to work out the units of k:
k=rate/[A]= $s^{-1}/moldm^{-3}=mol^{-1}dm^{3}s^{-1}$

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Borek

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(Original post by ApexT)
How would this differ from a second order reaction?

How does the concentration change in a 2^nd order reaction?

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