Graphs in Lecture

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John Huang 1G
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Graphs in Lecture

Postby John Huang 1G » Mon Feb 26, 2018 9:37 pm

Today, in lecture, Lavelle graphed two graphs. One graph was linear and the other was a curved graph. What is the difference between the two graphs???

Naveed Zaman 1C
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Re: Graphs in Lecture

Postby Naveed Zaman 1C » Mon Feb 26, 2018 10:00 pm

I can't exactly remember what the curved graph was for, but I can take a guess.

The linear graph depicted a first order reaction, where the natural log of the concentration of A (ln[A]) was plotted against time. This was called the integrated rate law for the first order reaction. Since the integrated rate law of a first order reaction:
ln[A] = -kt + ln [A]0
has the form of y = mx + b, the graph plots out like a line.

The second curved graph he showed us can be one of two things. The graph either showed just another way to represent the above graph, or it plotted different reactant concentrations as a function of time, like the ones he's been doing since Monday. My guess is that it's the former so I'll explain it really briefly.

Basically if you exponentiate both sides of the integrated rate law, you get:
[A] = [A]0e-kt
Here, if you plot [A] (instead of ln[A]) against t, you get a curved graph that models an exponential curve.

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Re: Graphs in Lecture

Postby Daniisaacson2F » Thu Mar 01, 2018 10:04 am

It depends which order you are talking about. For a first order reaction, the linear graph is the graph of ln[A] vs time, and the curved graph is just concentration vs time.

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