SunriseSunset
Hazard to Self
Posts: 82
Registered: 9-6-2015
Location: USA
Member Is Offline
Mood: No Mood
|
|
Finding Ka from pH question
In this video, this guy shows that from a diluted solution of Hypochlorous acid, he can use it's pH to determine the Ka.
https://www.youtube.com/watch?v=OA-f_8F5iNU
Once his instructions are completed, i took his result which is Ka = 3.47*10^-8
and used my calculator to find the negative log which gave me pKa = 7.46
Then when I look on wikipedia, it says the pKa of Hypochlorous acid is: 7.53
I'm wanting to be able to solve for Ka values from experimental data such as pH but is this minor margin of error still going to be accurate enough
for most eventual purposes? Maybe it would of been closer if he had a more accurate pH test. Anybody have suggestions? I don't know of any pH tests
that can determine more significant figures other than 0-14. The experimental pH he used for his calculation was already accurate down to 4.23 from a
0.1M solution. Thanks
What is the most accurate way to test pH that's out there? for being able to determine Ka values from a compound that doesn't have known data in
literature. So far the closest I've found are strips that go in .5 increments lol Is there any affordable product that yields .05 or .005 pH scale
accuracy?!
[Edited on 24-8-2015 by SunriseSunset]
Why do chemists call helium, curium and barium the medical elements?
because if you cant helium or curium, you barium! - Heimerdinger
|
|
|
DJF90
International Hazard
Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline
Mood: No Mood
|
|
A half decent pH probe will read to two decimal places. Be sure to calibrate before each use for accuracy.
|
|
|
DraconicAcid
International Hazard
Posts: 4334
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
A pH probe will read to two decimal places, but the actual pH will depend quite a bit on ionic strength, etc. The pH calculations taught in
first-year university courses is vastly simplified.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
PHILOU Zrealone
International Hazard
Posts: 2893
Registered: 20-5-2002
Location: Brussel
Member Is Offline
Mood: Bis-diazo-dinitro-hydroquinonic
|
|
Temperature is also important for pH just like CO2 in the air...this is especially true for weak acid-bases in the sensitive regio pH 6-8...
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
