Incomplete/ Reversible reaction

Mar3-06, 12:06 PM

A reversible reaction is a chemical reaction that may be reversed. In other words, the reactant and product of one reaction may reverse roles, without adding chemicals.

An incomplete reaction is a reaction in which neither of the reactants is depleted.

I didn't catch yet the difference between an incomplete and a reversible reaction.
I think they are the same.
Or there is any reaction that is incomplete but not reversible? Or one that is reversible but not incomplete?

**Astronuc** · Mar3-06, 12:34 PM

A reversible reaction could be complete, but the point is that even if complete, i.e. the reactants are 'completely' transformed into the products, it could be 'reversed', i.e. the products could be reconverted into the reactants, ostensibly by adding sufficient energy.

An incomplete reaction simply means that the reactants have not completely reacted. It says nothing about whether the reaction is reversible or not.

Mar3-06, 12:52 PM

An incomplete reaction simply means that the reactants have not completely reacted. It says nothing about whether the reaction is reversible or not.

I was thinking of that. But I wondered what could make the reactants to not completly react?

**Astronuc** · Mar3-06, 01:02 PM

The presence of products could interfere with the reaction, or the temperature could decrease, or pressure increase.

It all depends on what is driving the reaction.

On the other hand, it is likely to be a hypothetical situation. The objective here is to familiarize one with the terminology, so that one will use the correct statements as a professional.

I occasionally see poorly worded statements in papers, even refereed journals.

Mar3-06, 01:12 PM

Ok. Thank you again!

Summarizing:
A chemical reaction can be complete and reversible.
A chemical reaction can be incomplete and reversible.
It's wrong to say that all the reversible reactions are incomplete.
It's wrong to say that all the incomplete reactions are reversible.
Right?

I think my teacher said something similar to that 2 last sentences.

**Astronuc** · Mar3-06, 01:41 PM

I think it is matter of not confusing the two concepts.

One could have a reversible reaction that is either complete or incomplete, or one could have an irreversible reaction that is complete or incomplete.

An example of a reversible (partially) reaction is a rechargable storage battery. The reaction is complete when the battery is fully dead (drained). As long as it is incomplete, it can still provide a voltage and current. The storage battery can be 'recharged', but will never get back to a completely irreversible state, simply because that is the way nature is. So at best, the storage battery is partially reversible, but not completely so.

See - http://en.wikipedia.org/wiki/Reversible_reaction
http://en.wikipedia.org/wiki/Reversi...rmodynamics%29
http://en.wikipedia.org/wiki/Chemical_equilibrium
http://en.wikipedia.org/wiki/Le_Chatelier%27s_principle

**GCT** · Mar3-06, 10:14 PM

It's wrong to say that all the reversible reactions are incomplete.
It's wrong to say that all the incomplete reactions are reversible.
Right?

yeah, don't believe too much in the absolutes. Again, you'll need to read a standard p. chem. text, because the topic is extensive; chemical equilibrium, gibbs derivation, the fundamentals. I'm not quite sure what you're referring to by complete and incomplete.

**GCT** · Mar3-06, 10:18 PM

I've not encountered the term, "incomplete reaction" before. I'm guessing by an "incomplete reaction" they mean....an incomplete reaction, a reaction that's has not reached equilibrium. Not quite sure what they're going for here.

Mar4-06, 05:26 AM

I understand why you are not common with complete and incomplete terms for reactions. They are portuguese terms that I translated since I don't know the english ones and as you know my english is mediocre. I will translate the definitions, maybe it could help.

Complete reaction - A reaction in which one of the reactants gets concentration values not easily measured.

Incomplete reaction - A reaction in which neither of the reactants is depleted.

**Astronuc** · Mar5-06, 02:28 PM

Incomplete reaction - A reaction in which neither of the reactants is depleted. I had wondered if that was a possible meaning of 'incomplete'.

Which would infer that there is an excess of the reactant that is not depleted, and that is generally undesirable (wastes material).

Mar5-06, 02:35 PM

Which would infer that there is an excess of the reactant that is not depleted, and that is generally undesirable (wastes material).

But in an incomplete reaction there isn't a reactant that is depleted.

**GCT** · Mar5-06, 10:05 PM

I don't think that the term "incomplete reaction" is useful. What they may be referring to is pre-equilibrium, although all of this may be a failure to communicate the text effectively on your part.