How is alkali solution strength expressed?
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Dear XDJM users, I would like to ask how to distinguish the basic strength of NaOH solutions with concentrations of 5%, 10%, 15%, and 20%. I have measured them using a pH meter, and the values are roughly between 13.5 and 13.9, which doesn’t provide much information. Is there any other way to indicate this?
First, you need to know what pH value is. Next, you need to understand what you want to convey. Lastly, the mass percentage already clearly expresses the concept you intend to communicate
Reply to 2# zbx: Hello, thank you for your reply! What parameter can be used to represent the basicity of different alkali solutions? If another solvent, such as tetramethylammonium hydroxide, has a high degree of basicity, how can that be measured? How can its basicity be compared to that of NaOH solution?
This post was last edited by qugd on 2010-6-23 at 10:07. It is recommended that the original poster review the basic knowledge of acid-base theory. Distinguishing the strength of acids and bases is related, on the one hand, to the inherent chemical properties of the acid or base itself, and on the other hand, to the solvent as well. The strength of acids and bases is a completely different concept from their concentration. The concentration of an acid or base indicates the amount of solute present in a unit volume or weight of solvent. A high concentration does not necessarily mean strong acidity or alkalinity; it merely indicates the amount of acid or base required to neutralize the solution. The strength of an acid or base indicates its ability to donate or accept protons in a particular solvent (which is one of the explanations in acid-base theory); this ability is determined by the properties of the chemical substance itself as well as those of the solvent, and this is also the reason why different acid-base theories are needed to explain various phenomena. Furthermore, it was a huge mistake on the part of the poster to use a pH meter to test strong alkalis. pH generally refers to the acidity or alkalinity of dilute aqueous solutions. High concentrations of sodium hydroxide cause severe interference with pH electrodes, namely alkali error or sodium error. In many practical applications, we may use the concentration of acids or bases to represent their strength, but the method of representation must be appropriate and accurate. The concentration of a concentrated solution already indicates its characteristics, so there is no need to express them again using another concept that might be inaccurate, as that would lead to confusion or difficulty in understanding.
Reply to 4# qugd: Thank you for such a detailed response; I’ve learned a lot from it! I’ll take another close look at the relevant theoretical knowledge!