What is water acidic or basic salt

Experiment: neutral, basic, acidic salts

So far you have probably thought: "A neutralization produces a salt and water. We always use the reaction of sodium hydroxide solution with hydrochloric acid as a" prime example "for such a neutralization, which proceeds according to the following reaction equation:

$ NaOH _ {(aq)} + HCl _ {(aq)} \ to NaCl _ {(aq)} + H_ {2} O _ {(l)} $

Sodium chloride is neither acid nor alkali, and water is even more neutral, so the resulting sodium chloride solution should also be neutral, i.e. have a pH value of 7.

But there are many salts whose aqueous solutions have acidic or alkaline pH values. Such acidic or alkaline salts play an important role in everyday life. For example, if your garden soil is too acidic, sprinkle with calcium carbonate, an alkaline salt. And if you have heartburn because you ate too much or drank too much alcohol at the last party, take lime tablets or something similar the next morning. In contrast, many deodorants (deodorants) contain a rather acidic salt, namely the LEWIS acid aluminum chloride, which helps against unwanted perspiration. In addition to the alkaline sodium hydrogen carbonate, baking powder also contains disodium dihydrogen diphosphate, which reacts acidic.

In my own chemistry class, I first have my students perform experiment 4. I don't go to class wearing a household apron and a shopping basket full of different household salts - Isabelle Kuhn suggests this in her beautiful lecture Salts in the Household.

Attempt 4
Acid, neutral and basic salts

Various salts are dissolved in water; The pH value of the salt solutions is then determined with a pH meter.


The experiment shows that some salts actually react neutrally when they are dissolved in water. Some salts form an acidic solution, for example ammonium chloride, and other salts form an alkaline solution, for example sodium acetate. Of course, many salts also form a neutral solution, for example table salt.

To interpret this behavior, I have written three extra pages in which I explain in detail why this or that salt reacts neutral, alkaline or acidic.