Chemical Equivalence: Learn the Concept Easily

[Saitama]

Hello everyone!
I am not able to understand Chemical Equivalence? The bookish language is very hard to understand...
If someone could explain me the Concept Of Equilvalence, it would be very helpful for me...

Thanks,
Pranav

 

[Borek]

Do you know the definition?

 

[Saitama]

I don't know the definiton of Chemical Equivalence but i know the definition of A Chemical Eqivalent...

 

[Borek]

Now that you separated these two I realized something... In what context is the question asked? Chemical equivalent is used in stoichiometry, chemical equivalence is - for me at least, not I am not a native speaker - ambiguous, as it can be related either to use of equivalents, or to NMR...

 

[epenguin]

Wouldn't you agree Borek that

(i) roughly speaking maybe, equivalents are moles X valency? Often moles X charge.

(ii) the only time you need the concept is in trying to understand what other people who do use it are talking about? That you can understand and calculate everything you ever need to using moles? As long as you have an idea of what your reactions are so that one mole of one thing might react with one of another, but also with two of something else. Whereas one equivalent of one thing is always reacting with one equivalent of another by definition.

When I learned chemistry at school we got a basinful of equivalents, and were always calculating equivalent weights or number of equivalents and converting into molecular weights or moles and vice versa. The old textbooks full of them. I strongly suspect this was a hangover from (imposition of) late nineteenth century empiricist/operationalist philosophic-scientific dogma or pedantry in which you were not supposed to believe in atoms and molecules except as a calculating tool. So equivalences are a more strictly empirical concept, more closely related to actual elementary chemical experiment (titrations etc.) and observation. Yet they are more abstract to think about than molecules and moles. So I guess they have been done away with in teaching (you do not seem very familiarly with them ) as they were a torture for many students.

 

[Borek]

I have no problems with equivalents, just like I have no problems with normal concentrations. I am not sure if they are needed for anything, as everything they can be used for can be also calculated from stoichiometry. But then, there are many simplified concepts used by technicians (or engineers ) that survive in the labs, even if they are just bastardized versions of the real thing.

 

[Yanick]

There is also the concept of equivalence point when doing titrations (IE acid/base tirations and the equivalence point). That was the first thing that popped into my head, personally.

If equivalence is meaning only equivalents like in acid/base (which uses normality instead of molarity) or redox reactions its a different concept than the above.

I think this thread would be more useful to everybody if the OP would give some context to the question.

 

[Saitama]

This is the definition of Chemical Equivalent:-

An equivalent of a substance is defined as the amount of it which combines with the 1 mole of hydrogen atoms or replaces the same number of hydrogen atoms in a chemical reaction.

Further, there's a example:-
In the compounds HBr, H₂O and NH₃; one mole of H combines with one mole of Br, half mole of O and 1/3 mole of N respectively.

I don't understand how "one mole of Br, half mole of O and 1/3 mole of N" are calculated ?

 

[Borek]

Start with reaction equations. Bromine plus hydrogen, oxygen plus hydrogen, nitrogen plus hydrogen.