## First order graph

$\frac{d[R]}{dt}=-k[R]; \ln [R]=-kt + \ln [R]_{0}; t_{\frac{1}{2}}=\frac{0.693}{k}$

Amy Lefley 1J
Posts: 60
Joined: Fri Sep 28, 2018 12:15 am

### First order graph

When graphing a first order reaction, with time on the x-axis and ln(A) on the y-axis, the y-intercept is the natural log of the initial concentration of the reactant, but what does the x-intercept of this graph represent?

Gillian Murphy 2C
Posts: 30
Joined: Fri Sep 28, 2018 12:22 am

### Re: First order graph

time

Rachel-Weisz3C
Posts: 66
Joined: Fri Sep 28, 2018 12:23 am

### Re: First order graph

It represents time and it is usually measured in seconds, therefore rate = M/s, but it can also be measured in minutes, hours... depending on the reaction.

Heesu_Kim_1F
Posts: 60
Joined: Fri Sep 28, 2018 12:18 am

### Re: First order graph

The x-intercept (meaning y=0) of the first order graph would represent the time (usually in seconds) when the concentration of the reactant reaches 0, or essentially when there is no more reactant concentration left.
Hope this helps!

Megan_Ervin_1F
Posts: 78
Joined: Fri Sep 28, 2018 12:18 am

### Re: First order graph

If ln(A) vs Time is a straight line, then the reaction is a first order reaction

mbaker4E
Posts: 69
Joined: Fri Sep 28, 2018 12:26 am

### Re: First order graph

The x axis is time, usually in seconds but it can also be in minutes, days, etc.

varunhariharan
Posts: 30
Joined: Mon Jan 07, 2019 8:16 am

### Re: First order graph

The x-intercept shows how much time time (t) it takes for the natural log of [A] to equal zero, and for [A] to equal zero.

Nicole Lee 4E
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am
Been upvoted: 1 time

### Re: First order graph

The x-intercept would tell you the time at which all of your reactant A runs out.