[Shah]

what is the definition of complete? when to consider a reaction as complete? i.e for what equilibrium constant we consider a reaction is complete and not in equilibrium?

please help, Thanks

[rabolisk]

Complete means that the limiting reactant is used up all the way. An equilibrium constant would not be measurable for a "complete reaction" as it would approach infinity. If I don't see an equilibrium constant, and I have no reason to believe that it is an equilibrium reaction (e.g. weak acid dissociation) , then I assume that it goes to completion.

[Shah]

what you said is that what i was taught and believe, but actually i have read in a book that an acid-base reaction is considered as complete(quantitative) when its constant K is greater than 10^4. Is that right??? this is what confused me

thankssss

[rabolisk]

The author of the book certainly considers it complete when K > 10^4. But there is no arbitrary cutoff, certainly large K means the products are so overwhelming favored that the reaction has practically gone to completion. Don't worry too much about these arbitrary cutoff numbers. As long as you understand what a complete reaction is, you're good.