### Rate constant

Posted:

**Mon Mar 11, 2019 3:16 pm**Can rate constants be negative?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=144&t=44148

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Posted: **Mon Mar 11, 2019 3:16 pm**

Can rate constants be negative?

Posted: **Mon Mar 11, 2019 3:25 pm**

In Kinetics and for the scope of this class, the rate constant will never be negative. The Arrhenius equation is always positive (otherwise, the rate constant would be Zero). If the rate constant was zero then this would indicate that the reaction is not occurring at all. Please, someone, correct me if I am wrong otherwise hope this helps.

Posted: **Mon Mar 11, 2019 3:32 pm**

No, the rate constant will not be negative.

Posted: **Tue Mar 12, 2019 9:43 pm**

Rate constant k should always be positive.

From the Arrhenius Equation, we know k = A x exp(-Ea/RT).

"A" (frequency factor) will always be positive because (according to Google) there are no experimental cases where A is negative, and mathematically exp(-Ea/RT) can never be negative.

If rxn is 2nd order, line plot has a slope of +k.

If rxn is 1st or 0 order, line plot has a slope of -k.

From the Arrhenius Equation, we know k = A x exp(-Ea/RT).

"A" (frequency factor) will always be positive because (according to Google) there are no experimental cases where A is negative, and mathematically exp(-Ea/RT) can never be negative.

If rxn is 2nd order, line plot has a slope of +k.

If rxn is 1st or 0 order, line plot has a slope of -k.

Posted: **Tue Mar 12, 2019 11:19 pm**

the rate constant, k, will always be positive!