Chem Prac: Comparing pH of strong and weak acids (1 Viewer)

[let.me.die]

i was wondering if someone could explain to me something in my prac. using a ph probe we measured the pH of HCl and acetic acid at 0.1 and 0.01M. but i got a pH of 2.3 for HCl at 0.1M. i thought that HCl was a strong acid and would ionise completely so shouldnt it have a pH of 1? could someone explain this please.

we also had to calculate [H+] of the HCl and acetic acid. why is it that there is a higher [H+] at 0.01M than at 0.1M?

i would appreciate it if anyone could explain this to me.

 

[Riviet]

we also had to calculate [H+] of the HCl and acetic acid. why is it that there is a higher [H+] at 0.01M than at 0.1M?

It shouldn't be.... if you use the formula for calculating pH, -log₁₀[H+], -log(0.01)=2 and -log(0.1)=1. Remember that a pH of 1 is more acidic than a pH of 2, ie a higher conentration of H+ ions.

I'll let someone else answer that first question you had.

 

[desmond.thai]

It could be possible that the HCl solution you used was old and may have lost its acidity.

 

[pLuvia]

Also, you might have contaminated it with another substance

 

[insert-username]

Or your pH meter may have been incorrectly calibrated or slightly defective.


I_F

 

[pkc]

pH probes should be calibrated with 2 buffers (with buffer 2 and 7 in your case- for offset and slope), and never allowed to dry out (this is hard to guarantee in a school environment where caps can go missing or not filled with water).

Drying of the measuring glass tip will destroy the accuracy of a probe unless its rejuvenated with appropriate techniques.

 

[PoppyJoy]

Or you could have taken the reading too early
Cos the pH readings tend to decrease the longer u leave the probe in..getting more n more accurate

 

[minijumbuk]

lol don't worry. You'll never have to be asked to tell the true results in an exam. Just make up results that are theoretically right.

There could've been many sources of error in your practical, such as faulty equipment, contamination in acid, contamination on pH meter...

So yea, don't worry about this practical. Just learn the procedure of it, and make up results -they, the markers- want, not what you actually got in your experiment.

 

[samwell]

does HCl dissolve with water vapour when left open in a room or does it react with atmospheric compounds like CO2. kind of confused which is which. lol.

 

[cameron0110]

HCl will be slightly diluted with H2O in the atmosphere although 0.1 M HCl is so dilute it wouldn't make much of a difference at all.

The reactions with CO2 tend to be with NaOH because CO2 is an acidic oxide and so you get acid/base reactions occurring.

 

[miz2nv]

need help 4 chem we hve 2 make a model showing
hydrochloric acid and acetic acid any help with how they will look

please help