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Strength of Acids and Bases

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Teacher/Instructor Jacqueline Spivey
Jacqueline Spivey

Ph.D.,U.C.Santa Cruz
Teaching at a top-ranked high school in SF

She teaches general and chemistry at a top-ranked high school in San Francisco. Prior to that, she lead and published a number of research studies and lectured at SF State University.

The strength of acids and bases depend on how much an acid or base ionizes in solution. A strong acid or base completely ionizes in solution. In a neutralization reaction, an acid and a base react to produce a salt. A salt is an ionic compound whose cation comes from a base and whose anion comes from an acid.

Alright guys we're here talking about the strengths of acids and bases, so you recall that the definition of an acid if we're talking about the arrhenius definition is that it donates protons to solutions write an H+ and we're talking about a base it produces hydroxide ions or OH- in solution. Alright so basically the definition that have a strong acid or a strong base is that they completely ionize in solution and if you have a weak acid or a weak base they partially ionize in solution so right now I'm going to kind of get more into the strong acids strong base situation and discuss what it means for something to completely ionize in solution as dealing with weak acids and weak bases where there's only a partial disassociation is pretty complicated and not specific to the section.

So what does it mean for something to completely ionize in solution? Okay so not to get tripped up you know what an ion is it means that something is breaking into its partial positive components and negatively charged components so here HCl, hydrochloric acid, is an example of a common strong acid so HCl aqueous would completely disassociates into an H+ so an ion a proton and a chlorine ion right so you have plus and a minus for net zero charge okay so an example of a strong acid where you have completely disassociation of HCl into H+ and Cl-. Similarly, if we have a strong base a common strong base is sodium hydroxide, NaOH, aqueous would break up into its components positive sodium plus ion and a negatively chlorine ion and that's an example of a strong base so now you know what it means for something to completely ionize in solution.

So if we have a strong acid and a strong base, what happens if we mix them together? Well you get this idea of something that's called neutralization right so basically they cancel each other out so meaning that the products have none of the characteristics of either the acidic solution or the basic solution so when we get into talking about pH if we're talking HCl which you can find in your stomach acid has a pH of about 1 base is sodium hydroxide which has a much higher pH because its basic if something is neutral, that means it's pH 7 and that's how we know something is neutral so here again let's just look at the actual equation of mixing a strong acid and a strong base so we have HCl a strong acid and sodium hydroxide our strong base which if we put together in the same solution will give us water right because we know from our previous conversation about acid base reactions that water is the forward sorry it's a driving force of an acid base reaction the formation of water and we would also get formation of a salt. Okay so we now what water is now we know what a strong base and strong acid are so let's quickly just discuss what it means for something to be a salt.

Okay so salt sodium chloride table salt the stuff you put on your food with which we're very familiar, it just means that it's an ionic compound that has a positively charged ion and a negatively charged ion right so within sodium chloride the cation which is the sodium that comes from a base and the anion part comes from an acid.