Need help to translate some words.

[Guest kymoz]

Hi!

I am a french Canadian and I need some help from you to translate some french chemistry-related terms in English. My researches in french on google didn't satisfied me, and I wanted to look for english sites.

I'm only looking for translation of some terms to look for them on the net, but if anybody has the time to answer my question,s I would apreciate a lot. Here are the facts:

(Words surrounded bye " " are french words that I couldn't translate. I tried to aviod as much as I could.)

I'm studying chemistry in high-school and we have to do a report on the "titrage" (maybe those graphs will tell you what is "titrage": http://www.al.lu/chemistry/stuff1/EX1/notions/courbes.htm ) of an acid by a NaOH solution. This experiment is quite basic. But in my lab-report, I want to go deeper by explaining two things:

1-what does the "point d'Équivalence" means (I know that it is the point at which the H+ and OH- are in equivalent number, but I guess that there is more than this...) The "point d'équivalence" is the value on the graphs on this page in the green square : http://www.al.lu/chemistry/stuff1/EX1/notions/courbes.htm

2-Why is there a big and instant change in the pH when the mix (?) passes from acid to alcalinity? I know that mathematically, it is due to the fact that the reaction follows a logarithmic progresion, but what happens in terms of "ions" H+?

 

Thanks a lot for any further reply,

Kymoz

[akcapr]

the first defenition is titration. The "point d'Équivalence" is when all the acid has nuetralized all the base, or H+ = OH-. but thats all i can think of for that. For the last part i THink the curve is so rapid becasue a buffer has formed, and when the buffer capacity is exceded, it then contiunes to rapidly neutralize.

[Guest kymoz]

Thanks for the quick reply, Akcapr.

The "point d'équivalence" is effectively the neutralization of the acid by the base. But this is in a ideal situation, and it happens at pH=7. In our experience, this "point d'Équivalence" occurs at pH=8,67. We are doing the titration of acetic acid (CH3COOH) by sodium hydroxyd (NaOH). The acetic acid is a weak(?) acid. And the fact that the "point d'équivalence" is in a basic area is probably due to the fact that the CH3COO- is a basic ion(?). So this means that the "point d'Équivalence" doesn't reprensents the neutrality of the mix(?) because at 25C, the neutral pH is 7. I read that it represents the moment when the OH- have completely reacted with the H+, and the NaOH you add after this doesn't react anymore. But why doesn't it happens at pH=7?

Thanks again,

Kymoz

[akcapr]

thats a tricky one. But i am sure it has something to do with the fact that acetic acid is weak and NAOH is strong. SO perhaps the Point of "neutrality " shifts to the basic side for there is a strong base used.

[Guest kymoz]

After many researches in books, I finally found out the answer. I don't have a lot of time to explain for the moment, but I can post the whole explication on demand.

[Borek]

In general - for every titration - "point d'Équivalence" is called end point of titration, or just end point.

 

Best,

Borek

--

Chemical calculators for labs and education

http://www.chembuddy.com

BATE - pH calculations, titration curves

CASC - concentration conversions, solution preparation

[The Thing]

Idealy it would be the stoichiometric point.