3
$\begingroup$

I read somewhere that salts which do not contain a replaceable hydrogen or hydroxyl group are classified as normal salts. But I also know that strong base-weak acid salts are basic in nature.

$\endgroup$
7
$\begingroup$

Normal salts do not have to be neutral, and vice versa. There are two different features of a salt: (1) containing a replaceable hydrogen, and (2) making an acidic solution in water. They are not necessarily related. For example:

  • $\ce{NaHSO4}$ has both.
  • $\ce{NaHCO3}$ has the first and not the second (in fact, being a salt of a strong base and a weak acid, it has to be basic in nature, as you correctly recall).
  • On the other hand, $\ce{CuSO4}$ is partially hydrolyzed in water solution and hence has the second feature, but not the first.
  • To make the picture complete, $\ce{NaCl}$ has neither.

Likewise, the opposite features of (1) having a hydroxy group and (2) making a basic solution in water are even less related. For example:

  • $\ce{Cu2(OH)2CO3}$ has the first feature, but not the second (for it is not even soluble in water).
  • $\ce{CH3COONa}$ is partially hydrolyzed in water solution and hence has the second feature, but not the first.
  • $\ce{MgCl2}$ and $\ce{Mg(OH)2}$ form several basic salt phases with both features (J. Chem. Eng. Data 2017, 62 (4), 1384–1396). They are only sparingly soluble but still form measurably alkaline solutions, especially when warmed.
  • $\ce{MgSO4}$ has neither.
$\endgroup$
8
  • $\begingroup$ What about the particular case in the question? $\endgroup$
    – A J
    May 13 '18 at 13:45
  • 2
    $\begingroup$ Sodium acetate is hidden somewhere in my answer. $\endgroup$ May 13 '18 at 13:46
  • $\begingroup$ Okay so I get it...a salt is only neutral when it follows neither 1 not 2. Thanks :) $\endgroup$
    – A J
    May 13 '18 at 13:52
  • 2
    $\begingroup$ No, a salt is neutral when it doesn't follow 2, and normal when it doesn't follow 1. These things may or may not coincide. $\endgroup$ May 13 '18 at 13:54
  • 1
    $\begingroup$ Well, then chemistry is hard. Now to the point: sulfate ion does not hydrolyze in water, since it is a very weak base, like you said. As for the acetate ion and its basicity: without knowing the pKa of acetic acid, you wouldn't know that. $\endgroup$ May 13 '18 at 22:11
0
$\begingroup$

Since sodium acetate is the salt formed from sodium hydroxide (a strong base) and acetic acid (a weak acid) a solution of the salt should be alkaline.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.