Not every molecules i beg your pardon contain hydrogen are capable of donating protons. For example, methane (CH4) and also other hydrocarbons present no acidic properties at all. Carbon is not very electronegative, and so electron thickness is reasonably evenly mutual in a C―H bond, and also the hydrogen atom is i can not qualify to depart there is no at least one electron. Even when the is external inspection to extremely electronegative atoms favor oxygen or fluorine, a hydrogen atom is not constantly strongly acidic.

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Example (PageIndex1) : Proton Transfer

Acetic acid has the forecast formula

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There space a big number of weak acids, however fortunately they fall into a few well-defined categories:

Carboxylic acids

These compounds have the general formula RCOOH. Every react v water in the same way as acetic mountain . The toughness of carboxylic acids is dependency on the electronegative stamin of the atom in the "R" group. Consider the compounds F3COOH and also H3COOH. Fluorine is the most electronegative element, if hydrogen is comparable to carbon in electronegativity. Thus, the fluorines pull electron thickness away native the carboxyl group. This gets rid of electron density from the acidic oxygen-hydrogen bond, i beg your pardon weakens it. This weaker bond means that the hydrogen deserve to be removed more easily, which creates a more powerful acid. This ide can be used to any R group. The more electronegative the R group, the stronger the carboxylic acid will certainly be.

Weak oxyacids

These have actually the same general formula HnXOm as strong oxyacids, but the number of hydrogens is same to or one much less than the variety of oxygens. Because that a weak oxyacid, in various other words, m ≤ n + 1. Some instances are:

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Some of the weak oxyacids, H2CO3 for example, are really unstable and cannot be separated in pure type from aqueous solution.

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Other molecules containing acidic hydrogen atoms

Hydrogen fluoride (HF) has a very solid bond and does not donate that is proton as readily as various other hydrogen halides. Other molecules in this classification are hydrogen sulfide (H2S) and hydrogen cyanide (HCN). In the latter case, also though H is external inspection to C, the electronegative N atom pulls part electron thickness away, and also the HCN molecule is a really weak proton donor.

Hydrated cations

Cations, especially those of fee +3 or an ext or the the transition metals, space surrounded very closely by four to 6 water molecules in aqueous solution. An instance is Cr(H2O)63+, shown in figure (PageIndex1). The hopeful charge of the metal ion pulls electron thickness away indigenous the surrounding water molecules, weakening the hold of the oxygen atoms because that the hydrogen atoms. The latter have the right to consequently be much more easily donated as protons: