the solution of alkali metal in liquid nh3 is blue coloured due to the presence of solvated electrons.
the solution of alkali metal in liquid nh3 is blue coloured due to the presence of solvated electrons.
the solution of alkali metal in liquid nh3 is blue coloured due to?
the presence of solvated electrons
the alkali metals dissolve slowly in liquid ammonia, forming ammoniacal solutions of solvated m and e, which react to form hydrogen gas and the alkali metal amide (mnh, where m represents an alkali metal): this was first noted by humphry davy in 1809 and rediscovered by w. weyl in 1864. the process may be speeded up by a catalyst. similar solutions are formed by the heavy divalent alkaline earth metals calcium, strontium, barium, as well as the divalent lanthanides, europium and ytterbium. the amide salt is quite insoluble and readily precipitates out of solution, leaving intensely coloured ammonia solutions of the alkali metals. in 1907, charles krause identified the colour as being due to the presence of solvated electrons, which contribute to the high electrical conductivity of these solutions. at low concentrations (below 3 m), the solution is dark blue and has ten times the conductivity of aqueous sodium chloride; at higher concentrations (above 3 m), the solution is copper-coloured and has approximately the conductivity of liquid metals like mercury. in addition to the alkali metal amide salt and solvated electrons, such ammonia solutions also contain the alkali metal cation (m), the neutral alkali metal atom (m), diatomic alkali metal molecules (m) and alkali metal anions (m). these are unstable and eventually become the more thermodynamically stable alkali metal amide and hydrogen gas. solvated electrons are powerful reducing agents and are often used in chemical synthesis.
alkali metal
the production of pure alkali metals is somewhat complicated due to their extreme reactivity with commonly used substances, such as water. from their silicate ores, all the stable alkali metals may be obtained the same way: sulfuric acid is first used to dissolve the desired alkali metal ion and aluminium(iii) ions from the ore (leaching), whereupon basic precipitation removes aluminium ions from the mixture by precipitating it as the hydroxide. the remaining insoluble alkali metal carbonate is then precipitated selectively; the salt is then dissolved in hydrochloric acid to produce the chloride. the result is then left to evaporate and the alkali metal can then be isolated. lithium and sodium are typically isolated through electrolysis from their liquid chlorides, with calcium chloride typically added to lower the melting point of the mixture. the heavier alkali metals, however, is more typically isolated in a different way, where a reducing agent (typically sodium for potassium and magnesium or calcium for the heaviest alkali metals) is used to reduce the alkali metal chloride. the liquid or gaseous product (the alkali metal) then undergoes fractional distillation for purification. most routes to the pure alkali metals require the use of electrolysis due to their high reactivity; one of the few which does not is the pyrolysis of the corresponding alkali metal azide, which yields the metal for sodium, potassium, rubidium, and caesium and the nitride for lithium.
alkali metal