High-quality reactions allow to find any given ion, chemical or functional group. The corresponding reactants, indicators, in some cases – a torch flame are necessary for carrying out high-quality reactions.
High-quality reactions to cations and anions
To define a silver cation, it is necessary to carry out reaction with some chloride. Interaction of Ag (+) and Cl (-) gives as a result a white deposit of AgCl ↓. Ba2 barium cations + are found in reaction with sulfates: Ba (2+)+SO4(2-) =BaSO4 ↓ (white deposit). So truly and the return: to find chloride ions or sulfate ions in solution, it is necessary to carry out reaction, respectively, with salts of silver and barium.
For definition of cations of Fe (2+) use hexacyanoferrate (III) of K3 potassium [Fe(CN)6], to be exact, a complex ion [Fe(CN)6](3-). The formed dark blue deposit of Fe3 [Fe(CN)6]2 is called "a turnbullevy blue". For identification of cations of iron (III) take already hexacyanoferrate (II) of K4 potassium [Fe(CN)6] giving in interaction with Fe(3+) a dark blue deposit of Fe4 [Fe(CN)6]3 – "the Berlin azure". It is possible to find Fe(3+) also in reaction with NH4CNS ammonium thiocyanate. The low-dissociating thiocyanate of iron (III) – Fe(CNS)3 – is as a result formed and solution gains blood-red color.
The surplus of cations of H+ hydrogen creates acidic environment in which colourings of indicators respectively change: orange methyl orange and violet litmus become red. Many OH-hydroxide ions (alkaline environment) litmus becomes blue, methyl orange – yellow, and colourless phenolphthalein in neutral and sour environments gets crimson coloring.
To understand whether there is in solution a NH4+ ammonium cation, it is necessary to add alkali. In reversible interaction about NH4+ hydroxide ions gives NH3 ammonia ↑ and water. Ammonia has a characteristic smell, and the damp litmus piece of paper in such solution will turn blue.
In high-quality reaction to ammonia HCl reagent is used. In the course of education from ammonia and chlorohydrogen of chloride of HN4Cl ammonium it is possible to observe white smoke.
The carbonate - and a hydrocarbonate ions of CO3(2-) and HCO3 (-) can be found at acid addition. As a result of interaction of these ions with cations of hydrogen carbon dioxide is emitted and water is formed. At transmission of the received gas through 2 solutiongrows turbidCa (OH) lime water as insoluble connection – CaCO3 calcium carbonate ↓ is formed. At further transmission of carbon dioxide, sour salt – a hydrocarbonate of Ca(HCO3) 2 calcium soluble already is formed.
Reagent for detection S(2-) sulfide ions – the soluble salts of lead giving in reaction with S(2-) a black deposit of PbS ↓.
Detection of ions by means of a torch
Salts of some metals when entering into a flame of a torch paint it. This property is used in the qualitative analysis for detection of cations of these elements. So, Ca(2+) paints a flame in brick-red color, Ba(2+) - in flavovirent. Burning of salts of potassium is followed by a violet flame, a lity – bright red, sodium – yellow, strontium – carminic-red.
High-quality reactions in organic chemistry
Connections with double and threefold communications (alkenes, alkadienes, alkynes) decolour red-brown bromic Br2 water and pink solution of permanganate of KMnO4 potassium. Substances from two or more hydroksogruppama - OH (polyatomic alcohols, monosaccharides, disaccharides) dissolve in the alkaline environment a freshly cooked blue deposit of Cu (OH) 2, forming solution of bright blue color. With hydroxide of copper (II) also aldehydes, aldoza and the restoring disaccharides (aldehydic group) react, but already Cu2O deposit ↓ brick-red color drops out here.
Phenol in solution of chloride of iron (III) forms complex connection with FeCl3 and gives violet coloring. The substances containing aldehydic group give reactions of "a silver mirror" with ammoniac solution of oxide of silver. Iodine solution when entering starch into it becomes violet, and peptide communications of proteins are found in reaction with saturated solution of sulfate of copper and the concentrated caustic natr.