15.23 part C

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diangelosoriano
Posts: 49
Joined: Fri Sep 29, 2017 7:07 am

15.23 part C

Postby diangelosoriano » Wed Mar 07, 2018 11:25 pm

Determine the rate constant for each of the following first-order reactions:

Part C) 2A-->B+C,given that[A]0 =0.153molxL^-1 and that after 115 s the concentration of B rises to 0.034 molxL^-1.

I am confused as to where to start with this problem?

Tiffany Dao 1A
Posts: 32
Joined: Fri Sep 29, 2017 7:05 am

Re: 15.23 part C

Postby Tiffany Dao 1A » Thu Mar 08, 2018 12:23 am

you can find [A] at 115 seconds by converting the [B].
[A] = 0.153 molA/L - [0.034 molB/L x (2 molA/1 molB)]
then you can use ln[A] = -kt + ln{A]o

diangelosoriano
Posts: 49
Joined: Fri Sep 29, 2017 7:07 am

Re: 15.23 part C

Postby diangelosoriano » Thu Mar 08, 2018 12:29 am

Tiffany Dao 1A wrote:you can find [A] at 115 seconds by converting the [B].
[A] = 0.153 molA/L - [0.034 molB/L x (2 molA/1 molB)]
then you can use ln[A] = -kt + ln{A]o



Why do we subtract [0.034 molB/L x (2 molA/1 molB)]? Is there an equation on the formula sheet that we derive this from?

Xin He 2L
Posts: 38
Joined: Fri Sep 29, 2017 7:05 am

Re: 15.23 part C

Postby Xin He 2L » Thu Mar 08, 2018 2:58 am

We would subtract B from A because B is created from A, so when B increases, A decreases. After the subtraction, you'll find the new value for A which you then plug into the equation and solve for the time elapsed.


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