Does Salt Change the pH of Water?

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Salt won't change the pH of water because it doesn't give any reactions when added to water. Find out if sodium or chlorine changes the pH of water with help from a science teacher and field biologist in this free video on chemistry.

Part of the Video Series: Chemistry & Biology
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Video Transcript

Hi, I'm Brian with Today we're going to discuss how and if salt changes the pH of water. So, salt, if we take it as table salt, well salts in general are ionic compounds, and they tend to dissolve in water. And the question that we have to ask ourself, in terms of if it will change the pH, is once dissolved, whether or not the ions will react with water, which is hydrolysis and form a base, or an acid. So, let's examine salt, regular table salt and see what the answer is. So, table salt is made up of sodium and chlorine, and that breaks up into a sodium ion which is positively charged, and a chlorine ion, which is negatively charged. So the question we have to ask ourselves is whether or not sodium will react with water. First of all, sodium won't, because if it were to react, it would form a strong acid, sorry, a strong base, NaOH. Since strong acids and strong bases by definition, tend to totally break apart, that NaOH would simply go back to the ions. So, sodium won't react with water. Now we have to look at chlorine and see if that will react with water. Chlorine plus water is going to give us HCl. That's a strong acid. So as we just learned before, this reaction won't occur. So the end result is that adding table salt to water won't change the pH because you won't get any additional reactions. Now, there are instances where you will have a salt, a generic salt, change the pH of a, of a solution. So if you had sodium, I think this is sodium carbonate, Na2CO3, that breaks up to sodium and then CO3, two negative ions. The CO3 will then react with water, forming a weak acid and a base, OH negative. So, since it's forming a base, that's gonna, that's going to make the pH higher, which means make it more basic. So, adding sodium carbonate will change our pH. Now, an example of the opposite reaction occurring, if we had ammonium chloride, NH4Cl that breaks up into ammonium, NH4 positive, and chlorine, sorry chloride, Cl negative, so, and the ammonium will react with water, we know that chlorine won't because it would form a strong acid. But ammonium will, and it forms NH3 and then individual hydrogen protons, which we write as H3O, here, so since you're increasing the amount of hydrogen, in your solution, that makes it more acidic, and lowers the pH. So, as we've seen, adding regular table salt to water will not change the pH, but adding some other types of salts may.


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