Graphs of rate laws


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Baoying Li 1B
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Joined: Sat Aug 17, 2019 12:18 am

Graphs of rate laws

Postby Baoying Li 1B » Sun Mar 08, 2020 11:59 am

Hey, can someone describe the characteristics of the graph of rate laws? Like what’s the between the first order and the second order? What about the zero order?

Parker Smith
Posts: 102
Joined: Thu Jul 25, 2019 12:15 am

Re: Graphs of rate laws

Postby Parker Smith » Sun Mar 08, 2020 12:09 pm

A first order rate law forms a linear relationship when the natural log of [A] is plotted over time. A second d order rate law forms this relationship when 1/[A] is graphed over time. We derive these relationships from the integrated rate laws of each order of reaction. Since a 0th order rxn doesn't depend on the concentration, the relationship of simply [A] over time gives a linear graph

Aarja Pavade 1H
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Joined: Sat Aug 17, 2019 12:18 am

Re: Graphs of rate laws

Postby Aarja Pavade 1H » Sun Mar 08, 2020 1:51 pm

All of the graphs will be linear, but the slopes will vary. For instance, the graph of a first-order and zero-order reaction will have a decreasing slope of -k while a second-order reaction will have an increasing slope of k.

405268063
Posts: 102
Joined: Thu Jul 25, 2019 12:17 am

Re: Graphs of rate laws

Postby 405268063 » Sun Mar 08, 2020 2:04 pm

For zero order, the rate law makes a linear graph, which means that the rate just goes at constant k (slope). For first order reactions, the graph is also linear if you plot ln[A] versus time. For second order reactions, the graph is linear is you plot 1/[A] versus time.

MeeraBhagat
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Joined: Sat Aug 24, 2019 12:15 am

Re: Graphs of rate laws

Postby MeeraBhagat » Sun Mar 08, 2020 7:54 pm

Depending on the different rate laws for the different ordered reactions, plotting the corresponding term on the y-axis against time will yield a straight line instead of a curve. For example, if given a graph with the y-axis as 1/ln[A] plotted against time, and the graph is a straight line, then you know it is a second order reaction. The same goes for a first and zero order reactions with y-axis ln[A] and [A], respectively.

Gabriella Bates 2L
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Joined: Thu Jul 11, 2019 12:15 am

Re: Graphs of rate laws

Postby Gabriella Bates 2L » Sun Mar 08, 2020 8:01 pm

The graphs for the different rate laws will all be linear, but what is plotted on the y axis varies. For a 0th order reaction, [A] vs time is linear, and the slop is equal to -k. For a 1st order reaction, ln[A] vs time is linear and the slope is equal to -k. For a 2nd order reaction, 1/[A] vs time will be linear and the slope is equal to k. The differences are important because looking a the graph can help us determine the order of the rate law for a given reaction.

Justin Quan 4I
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Joined: Sat Sep 14, 2019 12:17 am

Re: Graphs of rate laws

Postby Justin Quan 4I » Mon Mar 09, 2020 1:19 pm

Here's a diagram depicting the graphs of the three rate laws, zeroth, first, and second order reactions. Image

105335337
Posts: 103
Joined: Sat Aug 24, 2019 12:15 am

Re: Graphs of rate laws

Postby 105335337 » Mon Mar 09, 2020 2:12 pm

If you graph [R] v time & get a straight line: zero order

if you graph ln[R] v time & get a straight line: first order

if you graph 1/[R] v time & get a straight line: second order

pmokh14B
Posts: 107
Joined: Sat Aug 17, 2019 12:15 am

Re: Graphs of rate laws

Postby pmokh14B » Mon Mar 09, 2020 2:16 pm

The first order graph is of ln[A] vs time, and the second-order is 1/[A], whichever is linear is the order of the reaction.


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