rate constants


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Fdonovan 3D
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rate constants

Postby Fdonovan 3D » Sun Mar 01, 2020 9:39 pm

Are rate constants always positive? And if so why is this the case?

Jonathan Gong 2H
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Re: rate constants

Postby Jonathan Gong 2H » Sun Mar 01, 2020 9:48 pm

Rate constants, k, should be positive since they relate given concentrations with the rate of a reaction, which will always be positive. But, if you are considering graphs, a plot of a 1st or 0 order reaction will have a slope of -k, while a plot of a 2nd order reaction will have a slope of +k.

lilymayek_1E
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Re: rate constants

Postby lilymayek_1E » Sun Mar 01, 2020 9:55 pm

the rate constant (which is k) should always be positive; you can think of a rate as always positive because k (a proportion between concentrations) is positive, and rate can be presented as K[R]^n, which must be positive as negative concentration or proportions cannot exist.
on a graph of a first-order reaction, the slope is negative, but we have to add a negative sign to the overall rate to accommodate for this downward slope (the rate itself isn't negative)

Abigail_Hagen2G
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Re: rate constants

Postby Abigail_Hagen2G » Fri Mar 06, 2020 11:04 pm

Rate constants are always positive because concentrations are always positive.

205405339
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Joined: Thu Jul 11, 2019 12:16 am

Re: rate constants

Postby 205405339 » Fri Mar 06, 2020 11:27 pm

rate constants are always positive and don't have units

Joanne Lee 1J
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Re: rate constants

Postby Joanne Lee 1J » Sun Mar 08, 2020 2:02 pm

Yes, rate constants are always positive because they represent concentration and concentration has to always be positive.

Louise Lin 2B
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Re: rate constants

Postby Louise Lin 2B » Sun Mar 08, 2020 2:30 pm

yes rate constants are always positive because even when reactions slow down or reverse, the rate from product to reactant is still moving forward, making the rate constant positive.

aishwarya_atmakuri
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Re: rate constants

Postby aishwarya_atmakuri » Sun Mar 08, 2020 2:44 pm

Yes, rate constants are always positive because they represent concentration which is based on mass (always positive).

rabiasumar2E
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Re: rate constants

Postby rabiasumar2E » Sun Mar 08, 2020 3:04 pm

Yes! Rate constants are always positive because concentrations cannot be negative values.

Jasmine W 1K
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Re: rate constants

Postby Jasmine W 1K » Sun Mar 08, 2020 5:05 pm

Rate constants are always positive because concentrations cannot be negative.

Leila_4G
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Joined: Sat Sep 14, 2019 12:17 am

Re: rate constants

Postby Leila_4G » Sun Mar 08, 2020 5:10 pm

In what case would we ever get a negative rate constant?

Leila_4G
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Joined: Sat Sep 14, 2019 12:17 am

Re: rate constants

Postby Leila_4G » Sun Mar 08, 2020 5:11 pm

Also, will we ever get a graph with a curve of lnA/t even if we have the correct order reaction? I thought I saw an example like that in the book but I was confused.

kristi le 2F
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Re: rate constants

Postby kristi le 2F » Sun Mar 08, 2020 6:34 pm

Rate constants will be positive, but you can still get a graph with a negative slope, such as in 1st order reactions where the slope is -k.

Nare Nazaryan 1F
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Re: rate constants

Postby Nare Nazaryan 1F » Sun Mar 08, 2020 11:37 pm

Since rate constants depend on concentration (which is positive), they are always positive.

Maika Ngoie 1B
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Joined: Fri Aug 02, 2019 12:16 am

Re: rate constants

Postby Maika Ngoie 1B » Wed Mar 11, 2020 4:27 pm

Because concentration can never be a negative value, it is always positive.

EMurphy_2L
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Joined: Sat Sep 07, 2019 12:16 am

Re: rate constants

Postby EMurphy_2L » Wed Mar 11, 2020 4:39 pm

Leila_4G wrote:In what case would we ever get a negative rate constant?

for 0 or 1 order reactions in which the slope is negative!

Samuel Tzeng 1B
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Re: rate constants

Postby Samuel Tzeng 1B » Wed Mar 11, 2020 4:41 pm

the rate constant is always positive

Celine 1F
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Re: rate constants

Postby Celine 1F » Thu Mar 12, 2020 2:09 pm

Rate constants should always be positive

Diana Andrade_4F
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Joined: Tue Nov 05, 2019 12:18 am

Re: rate constants

Postby Diana Andrade_4F » Fri Mar 13, 2020 10:18 pm

Yes, they're always positive!

Anthony Hatashita 4H
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Joined: Wed Sep 18, 2019 12:21 am

Re: rate constants

Postby Anthony Hatashita 4H » Fri Mar 13, 2020 10:31 pm

Rate constants are always positive because they are based off time and concentrations which are always positive.


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