### Slopes of a plot

Posted:

**Sun Mar 17, 2019 4:04 pm**Is the slope of a plot of a first order negative?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=148&t=45263

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Posted: **Sun Mar 17, 2019 4:04 pm**

Is the slope of a plot of a first order negative?

Posted: **Sun Mar 17, 2019 4:25 pm**

yes it is

Posted: **Sun Mar 17, 2019 4:45 pm**

Since first order is ln[A]=-kt+ln[A]o it has a negative slope due to the -k.

Posted: **Sun Mar 17, 2019 10:51 pm**

The only one that isn't -k is is 2nd-order, which is just k (+k).

Posted: **Sun Mar 17, 2019 10:54 pm**

Zero Order also has a negative slope. Think of the equations as mx+b. The Slope (mx) is similar to kt in the order process formulas.

Posted: **Sun Mar 17, 2019 10:58 pm**

Yes, both zero and first order reactions' linear plots have slope as -k.

Posted: **Fri Feb 28, 2020 8:05 pm**

Yes the graph of the first order has a negative slope. The slope is -k and since k is always positive the slope is always negative for 1st order.

Posted: **Fri Feb 28, 2020 11:20 pm**

Zeroth Order plot is negative (-k). First order plot is negative (-k). Second order plot is positive (+k). Also Lavelle hasn't discussed it yet I believe, but the units of the rate constant k in Zeroth Order is M/s, in First Order is 1/s, and Second Order is M^-1* s^-1