Properties of acids

Do not underestimate the role of acids in our lives,because many of them are simply irreplaceable in everyday life. First, let's remember what acids are. These are complex substances. The formula is written as follows: HnA, where H is hydrogen, n is the number of atoms, and A is the acid residue.

The main properties of acids include the possibilityreplace molecules of hydrogen atoms with metal atoms. Most of them are not only corrosive, but very toxic. But there are also those with which we come across constantly, without harm to one's health: vitamin C, citric acid, lactic acid. Let's consider the basic properties of acids.

Physical properties

The physical properties of acids often help to findthe key to determine their nature. Acids can exist in three forms: solid, liquid and gaseous. For example: nitric (HNO3) and sulfuric acid (H2SO4) are colorless liquids; Boron (H3BO3) and metaphosphoric (HPO3) - solid acids. Some of them have color and smell. Different acids dissolve in water differently. There are also insoluble: H2SiO3 - silicon. Liquid substances have a sour taste. The name of some acids produced the fruits in which they are: malic acid, citric acid. Others received their name from the chemical elements contained in them.

Classification of acids

Typically, acids are classified according to several characteristics. The very first - this is, according to the oxygen content in them. Namely: oxygen containing (HClO4 - chlorine) and anoxic (H2S - hydrogen sulphide).

By the number of hydrogen atoms (by basicity):

• Monobasic - contains one hydrogen atom (HMnO4);
• Dibasic - has two hydrogen atoms (H2CO3);
• Three-base, respectively, have three hydrogen atoms (H3BO);
• Polybasic - have four or more atoms, are rare (H4P2O7).

By classes of chemical compounds, are divided intoorganic and inorganic acids. The first, mostly found in products of vegetable origin: acetic, lactic, nicotinic, ascorbic acid. Inorganic acids include: sulfuric, nitric, boric, arsenic. The range of their application is quite wide from industrial needs (the manufacture of dyes, electrolytes, ceramics, fertilizers, etc.) before cooking or sewage cleaning. Also, acids can be classified according to strength, volatility, stability and solubility in water.

Chemical properties

Let's consider the basic chemical properties of acids.

• The first is interaction with indicators. As indicators, litmus, methylorange, phenolphthalein and universal indicator paper are used. In acid solutions, the color of the indicator changes color: litmus and universal ind. the paper will turn red, methyl orange, and phenolphthalein will remain colorless.
• The second is the interaction of acids with bases. This reaction is also called neutralization. The acid reacts with the base, as a result of which we have salt + water. For example: H2SO4 + Ca (OH) 2 = CaSO4 + 2 H2O.
• Since almost all acids are readily soluble inwater, neutralization can be carried out with both soluble and insoluble bases. An exception is silicic acid, it is almost insoluble in water. To neutralize it, such bases as KOH or NaOH (they are soluble in water) are required.
• The third is the interaction of acids with basicoxides. There is also a neutralization reaction. The basic oxides are close "relatives" of the bases, therefore, the reaction is the same. We very often use these oxidizing properties of acids. For example, to remove rust from pipes. The acid reacts with the oxide, turning into a soluble salt.
• The fourth is reaction with metals. Not all metals react equally well with acids. They are divided into active (K, Ba, Ca, Na, Mg, Al, Mn, Zn, Cr, Fe, Ni, Sn. Pb) and inactive (Cu, Hg, Ag, Pt, Au). It is also worth paying attention to the strength of the acid (strong, weak). For example, hydrochloric and sulfuric acids are able to react with all inactive metals, and citric and oxalic acids are so weak that they react very slowly even with active metals.
• The fifth is the reaction of oxygen-containing acids onheating. Almost all acids of this group decompose into oxygen oxide and water when heated. The exception is coal (H3PO4) and sulfurous acid (H2SO4). When heated, they decompose into water and gas. It must be remembered. That's all the main properties of acids.