SL Chemistry IA Activation Energy Uncertainty

[potatohead]

 

Hello everyone, I'm wondering how I would calculate the uncertainty of my findings for a lab report.

I found the activation energy of the alka seltzer reaction in water (C₆H₈O₇＋3NaHCO₃ → 3H₂O＋3CO2＋Na3C6H5O7)

The way I found it was to measure pressure change over time in a closed erlenmeyer flask, convert that to concentration (using ideal gas law), and take its inverse over time to graphically find the rate constant. Then, I took the natural log of the rate constant against the inverse of time (aka the Arrhenius equation) to give me Ea times r. I divided the slope of the graph by R to give me Ea. However, now I'm confused about where to begin with apparatus uncertainty and how it factors into my calculations.

I have the uncertainty of the digital stopwatch, of the pressure probe, of the graduated cylinder used for measuring, of the electronic balance and the thermometer (the trials were done at various temperatures).

So where do I even begin with this? Sorry if my explanation is weird, but I can share my document with you if you are able to explain to me how I would start.

If you like, I can add the uncertainties of the apparatus for context. I dont understand how to incorporate the uncertainty of the stopwatch at all, since i'm measuring pressure in 15 second increments first.

 

 

[plshelpibcraz]

On 3/20/2020 at 6:49 PM, potatohead said:

 

Hello everyone, I'm wondering how I would calculate the uncertainty of my findings for a lab report.

I found the activation energy of the alka seltzer reaction in water (C₆H₈O₇＋3NaHCO₃ → 3H₂O＋3CO2＋Na3C6H5O7)

The way I found it was to measure pressure change over time in a closed erlenmeyer flask, convert that to concentration (using ideal gas law), and take its inverse over time to graphically find the rate constant. Then, I took the natural log of the rate constant against the inverse of time (aka the Arrhenius equation) to give me Ea times r. I divided the slope of the graph by R to give me Ea. However, now I'm confused about where to begin with apparatus uncertainty and how it factors into my calculations.

I have the uncertainty of the digital stopwatch, of the pressure probe, of the graduated cylinder used for measuring, of the electronic balance and the thermometer (the trials were done at various temperatures).

So where do I even begin with this? Sorry if my explanation is weird, but I can share my document with you if you are able to explain to me how I would start.

If you like, I can add the uncertainties of the apparatus for context. I dont understand how to incorporate the uncertainty of the stopwatch at all, since i'm measuring pressure in 15 second increments first.

 

 

hey how did your ia end up turning out in terms of comparison to literature values cuz im thinking of using a similar method