In our daily life, we cannot live without chemicals. In theory, all the chemical compounds have alkalinity or acidity. So you may wonder what are the strong acids and weak acids, strong bases and weak bases.
The ionization constant of acid in aqueous solution is the standard of the strong acid now. In general, the pKa of the strong acid (the acidity coefficient, the negative log of the ionization constant) is less than 1.
Strong acids mainly refer to permanganic acid, hydrochloric acid (hydrochloric acid), sulfuric acid, nitric acid, perchloric acid, selenoic acid, hydrobromic acid, hydroiodic acid, and chloric acid. They all can lead to severe stimulation and corrosion, and can cause serious burns when contacting to the body and should be washed with water or soda. But it's quite interesting that carbon borane acid, the strongest super acid, is not corrosive and can be held in your hand!
Inorganic strong solids include:
Sulfuric acid (H2SO4), nitric acid (HNO3), perchlorate (HClO4), hydrochloric acid (HCl), hydrobromic acid and hydroiodic acid (HI), high bromate (HBrO4), chlorate (HClO3), bromate (HBrO3), fluosilicate (H2SiF6), chlorine lead-acid (H2PbCl6), partial (HPO3), osmic acid phosphate, permanganate (HMnO4), selenium acid (H2SeO4), high-speed acid (H2FeO4), fluoboric acid (HBF4), fluoride sulfonic acid (HSO3F), cyanate (HOCN), thiocyanate (HSCN), high iodate (HIO4).
Organic strong acids include:
2,4,6-trinitrobenzoic acid , trifluoroacetic acid (TFA, CF3COOH), trichloroacetic acid (CH3SO3H), benzenesulfonic acid (C6H5SO3H), KMD acid (cyclohexanethiol sulfonic acid), 2-chloroethanethiol (CH3CHClSH, generally regarded as strong acid).
And here is a part of the super acid list:
Antimony fluoride sulfonic acid (SbF6SO3H), perfluorinated sulfonic acid resin, chlorine, fluorine aluminate (HAlCl3F, including complex ion AlCl3F-), carbon borane acid, solid super acid, such as FeCl3 · HClO4, SiO2 · nH2O.
The pKa of the strong acid (the acidity coefficient, the negative log of the ionization constant) is more than 4. Weak acids can not completely ionize in solution. If you use the usual HA to indicate the acid, there is still a good amount of HA in the solution in addition to ionizing the proton H+ in the aqueous solution. Here is the formula: HA(aq)↔H+(aq)+A-(aq). When the solution is in equilibrium, the relationship between reactants and prod ucts can be expressed as follows:
The larger the Ka (or the smaller the pKa value) is, the more hydrogen ions (H+) are formed, and the smaller the pH will be. Except for a few acids that are defined as strong acids or super strong acids, most of the acids are weak acids.
Organic acid is also an important part of weak acid. Common household weak organic acids include acetic acid in vinegar, lemons and citric acid in many raw fruits, inorganic acid such as boric acid used as an antimicrobial agent, and the carbonic acid used in sodas.
Common weak acids are like H2SiO3, HCN, H2CO3, HF, CH3COOH, H2S, HClO, HNO2, H2SO3 and so on.
A strong base usually refers to a substance that can change the color of a particular indicator, in a standard case (with a concentration of 0.1 mol/L) and a pH of more than 7. All ions ionized in aqueous solutions are hydroxide ions, which react with acids to form salts and water.
The so-called strong base and weak base are relative---- alkali dissolved in water can completely disassociate belongs to strong base. Strong alkali is divided into organic strong base and inorganic strong base. Alkali is highly corrosive.
In organic strong alkali, organic metal compounds are the most alkaline, such as organic metal lithium compounds (such as butyl lithium, diisopropyl ammonium lithium, benzyl lithium, etc.), grignard reagent, alkyl copper lithium, etc.
In inorganic strong alkali, amino compounds (such as amino potassium, amino sodium) and alkali metal hydride (NaH, KH, etc.) are the most alkaline, and then the following is hydroxide. Alkaline metals and some alkaline-earth metals are usually strong bases, too.
Alkali metal hydroxides are like LiOH, NaOH, KOH, RbOH, CsOH, FrOH.
Alkaline earth metal hydroxides are like Ca(OH)2, Sr(OH)2, Ba(OH)2, Ra(OH)2.
Other strong alkalis are like Hg(OH)2, TlOH, Tl(OH)3, AgOH·2NH3, HOCH2CH2N(CH3)3(OH).
A weak base is a base that is not completely ionized after water, which means that the proton reaction of it is incomplete. The pH of the weak base is greater than 7 but closer to 7.
Compared with strong base, the weak base is less able to accept the proton from the water molecule, so the H+ concentration in the solution is higher and the pH value is lower. Weak base is not necessarily insoluble in water, for example, NH3·H2O is easily soluble in water, but it is not completely ionized in water, so NH3·H2O belongs to weak base.
A base that cannot be completely ionized in solution is usually formed by a non-reactive metal (or NH3), such as Al(OH)3, Cu(OH)2, Fe(OH)2, Fe(OH)3, Zn(OH)2and other insoluble bases.
Here is a part of the list of weak bases:
NH3·H2O, aluminum hydroxide: Al(OH)3, Cu(OH)2, Fe(OH)2, Fe(OH)3, zinc hydroxide: Zn(OH)2, AgOH and so on.
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