What are Strong Acids?

 Hello fam, i believe that the journey so far have been nothing short of an exciting ride. We want to delve today into understanding what we mean by a strong acid. When we talk about "strong", our mind would obviously go to something that is not faint or feeble in its appearance. That idea would partially help the discussion that is at hand. 


A strong acid is an acid that dissociates completely in solution. What does that mean? I think the key word to explain here is the term "dissociate" when we talk about dissociation in chemistry, we mean that the substance can be broken up to form ions. Let me give you an example using three common acids;

HCl(aq) ---> H^+(aq) + Cl^-(aq)

H2SO4(aq) ----> 2H^+ (aq) + SO4^2-(aq)

HNO3(aq) ----> H^+(aq) + NO3^-(aq)


Looking at the examples that I have given above, we can see that the unique thing is that the compounds all break up in solution and there is no trace of the molecular substance in solution. What i mean is that, once we add HCl to water, the substance no longer exists as HCl in the solution. All we see in the solution are the ions that make up HCl which are H^+ and Cl^-. We can not see anymore HCl in the solution!


Any acid that behaves in such a manner that the molecule breaks up in water such that we do not have even the slightest trace of it in solution rather all we have would be the ions that make up the acid is what we call a strong acid.


I know that you have raised your eyebrows when I said that we can not "see" the molecules in solution. You would ask me like one student did years ago; "Uncle Jude,  how can I see molecules?" My answer was simple, "I wish I could but unfortunately,  I can't!"


How then do I know that the molecule is completely dissociated? I would need to look at the conductivity data for the solution. Remember that the acid was dissolved in water to form the acid solution. If I measure the conductivity of water using a conductivity meter before adding the acid and measure it again after adding the acid, I would notice that the conductivity of the solution of the acid in water would be far higher than the conductivity of the ordinary water. Since the conductivity of a solution is increased by the presence of more ions in solution, it follows that 99% or more of the ions in HCl were dissociated when dissolved in water. This is why HCl is called a strong acid. The same logic applies to all strong acids.


Hope you learnt something today?


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