The ammonium acetate is an inorganic salt whose chemical formula is NH4CH3COOH. It is derived from a mixture of acetic acid, present in commercial vinegar at a concentration of 5%, and ammonia. Both starting substances have characteristic odors, so it is possible to get an idea why this salt smells like vinegar-ammonia.
However, the most outstanding aspect of this salt is not its smell, but its low melting point. It is so low that in any laboratory it could be obtained in its liquid version, where ions flow freely to transport electrical charges..
On the other hand, ammonium acetate is deliquescent; that is, it absorbs water or humidity from the environment until it dissolves completely. That is why, although in anhydrous state its crystals are white, they quickly turn bright (like the ones in the beaker in the image above).
Being a solid source of ammonia, it should be handled in such a way as to minimize inhalation of its vapors. But, despite this negative characteristic, the NH4CH3COOH is useful for the preparation of buffer solutions that preserve food, as well as being a component of certain protein extracting solvents.
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The image above shows the ions that make up ammonium acetate in a spheres and rods model. On the left is the cation of tetrahedral geometry, NH4+, while on its right the molecular anion with two electrons delocalized between two oxygen atoms, CH3COO- (the dotted line between the red spheres).
So both ions, NH4+ and CH3COO-, they are held together by their electrostatic attraction that, together with the repulsions between equal charges, end up defining a crystal. This ammonium acetate crystal has an orthorhombic structure, which could be observed in microscopic samples or even of visible sizes..
Not only is ionic bonding important for this salt, but so are hydrogen bonds. NH4+ you can donate up to four of these bridges; that is, in each of the vertices of its tetrahedron there is an oxygen atom from a CH3COO- neighbor (H3N+-H- OCOCH3).
In theory, the forces within your crystals should then be very strong; but experimentally the opposite occurs, since it only melts at 114 ° C. Therefore, hydrogen bonds do not compensate for the weak ionic bond, nor the low lattice energy of the NH orthorhombic crystal.4CH3COO.
It was originally said that ammonium acetate is prepared by mixing acetic acid and ammonia. Therefore, salt can also be expressed as: NH3CH3COOH. Thus, depending on the composition, other structures can be obtained: NH32CH3COOH, or NH35CH3COOH, for example.
Also, it was mentioned that it absorbs quite a bit of moisture. In doing so, it incorporates water molecules into its crystals, which hydrolyze to give NH3 or CH3COOH; and that is why the salt emits the smell of ammonia or vinegar.
Deliquescent white crystals with a vinegar and ammonia odor.
77.083 g / mol.
1,073 g / mL at 25ºC.
114 ° C. This value is considerably lower compared to other salts or ionic compounds. In addition, it lacks a boiling point due to the formation of ammonia, implying the decomposition of salt..
143 g / 100 mL at 20 ° C. Note its extraordinary solubility in water, which shows the affinity felt by water molecules for NH ions.4+ and CH3COO-, hydrating them in aqueous spheres.
Its solubility is not such in less polar solvents. For example, in 100 mL of methanol at 15ºC, 7.89 g of NH are dissolved4CH3COO.
It is deliquescent, so you should avoid storing in humid spaces. Also, while absorbing water, it releases ammonia, and therefore decomposes.
9.9.
This constant corresponds to the acidity of the ammonium ion:
NH4+ + B <=> NH3 + HB
Where HB is a weak acid. If the base B is about water, it will have its hydrolysis reaction:
NH4+ + HtwoOR <=> NH3 + H3OR+
In which the species H3OR+ defines the pH of the solution.
On the other hand, acetate also contributes to pH:
CH3COO- + HtwoOR <=> CH3COOH + OH-
Thus, both species H3OR+ and OH- they are neutralized giving a neutral pH 7. However, according to Pubchem, highly concentrated ammonium acetate solutions have an acidic pH; which means that NH hydrolysis predominates4+ on the CH3COO-.
ΔFH298 = -615 kJ / mol.
Aqueous solutions of sodium acetate allow lead, iron and zinc sulfates to be solubilized, to later determine their concentration by atomic absorption spectroscopy..
As it melts at a low temperature compared to other salts, its liquid can be used to conduct the electric current that lights the circuit of a light bulb..
It can regulate pH changes in acidic or basic ranges, which is used to maintain a constant pH in, for example, meats, chocolates, cheeses, vegetables or other food products.
It is a relatively cheap and biodegradable salt, used to de-ice icy roads. Likewise, as it is a source of water-soluble nitrogen, it is used for agricultural purposes to determine potassium levels..
This salt is used to precipitate proteins for chromatographic analysis..
Ammonium acetate works as a diuretic agent in veterinary medicine, and is also a necessary salt for the synthesis of insulin and penicillin.
Next, and finally, some risks or negative consequences caused by ammonium acetate are listed:
- May cause mild skin irritation, but not absorbed into it.
- When ingested it causes stomach upset, diarrhea, diuresis, anxiety, increased need to urinate, tremors and other symptoms related to ammonia poisoning, as well as damage to the liver.
- Inhalation irritates the nose, throat and lungs.
For the rest, it is unknown if it can cause cancer, and any possible risk of fire from this salt is ruled out (at least under normal storage conditions)..
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