Alkali metals are not characterized by (A) good conductor of heat and electricity (B) high oxidation potentials (C) high melting points (D) solubility in liquid ammonia

Name a non-metal that is : a good conductor of heat and electricity,

Give reasons for the following Electrovalent compounds are soluble in water, insoluble in organic solvents, good conductors of electricity in molten or aq.solution state, have high meltimg points and undergo electrolytic dissociation on pasaage of electric current, while covalent compounds are soluble in organic solvents, insoluble in water, non-conductors of electricity, have low melting points & undergo ionisation on passage of electric current.

Alkali &alkaline earth metals have low ionisation enthalpies and hence exhibit characteristic flame colouration. They have high negative electrode potentials & hence are strong reducing agents. It dissolve in liquid ammonia to give a solution which conducts electricity and act as strong reducing agent. being stronger reducing agent than hydrogen, they are usually prepared by the electrolysis of their fused chlorides. Their oxides are basic and the basic strength increases down the group. The solubility of carbonates and sulphates of alkali and alkaline earth metals show opposite trends. only the carbonates of Li and alkaline earth metals decompose on heating. The bicarbonates of both alkali & alkaline earth metals on heating give carbonates. Which of the following process is used in the extractive metallurgy of sodium?

Metal with low melting point containing impurities of high melting point can be purified by

Metal with low melting point containing impurities of high melting point can be purified by

Assertion: Aluminothermy is used for extraction of chromium form chromium oxide. Reason: Alumina has a high melting point.

Alkali metals oxide are obtained by combustion of the metals.Although Na normally gives Na_2O_2 ,it will take up further oxygen at elevated pressure and temperature to form NaO_2 .The per and superoxides of the heavier alkalies can also be prepared by passing stoichiometric amounts of oxygen into their solution in liquid ammonia. The different alkali metal oxides can be distinguished by reaction with water.The superoxides reacts with CO_2 and give oxygen gas.The stability of per and superoxides is based upon that larger cation can stablise larger anion, due to larger lattice energy. Alkali metals dissolve in liquid ammonia.Dilute solutions are dark blue in colour but as the concentration increases above 3M, the colour changes to copper bronze and the solution acquires the metallic lusture due to the formation of metal ions clusters.The solutions of alkali metals in liquid ammonia are good conductors of electricity due to the presence of ammoniated cations and ammoniated electrons.However, the conductivity decreases as the concentrations increases, since ammoniated electrons and ammoniated cation associate. Solution of sodium metals in liquid ammonia is strongly reducing due to the presence of :

Alkali metals oxide are obtained by combustion of the metals.Although Na normally gives Na_2O_2 ,it will take up further oxygen at elevated pressure and temperature to form NaO_2 .The per and superoxides of the heavier alkalies can also be prepared by passing stoichiometric amounts of oxygen into their solution in liquid ammonia. The different alkali metal oxides can be distinguished by reaction with water.The superoxides reacts with CO_2 and give oxygen gas.The stability of per and superoxides is based upon that larger cation can stablise larger anion, due to larger lattice energy. Alkali metals dissolve in liquid ammonia.Dilute solutions are dark blue in colour but as the concentration increases above 3M, the colour changes to copper bronze and the solution acquires the metallic lusture due to the formation of metal ions clusters.The solutions of alkali metals in liquid ammonia are good conductors of electricity due to the presence of ammoniated cations and ammoniated electrons.However, the conductivity decreases as the concentrations increases, since ammoniated electrons and ammoniated cation associate. On dissolving smaller (less than 3M) amount of sodium metal in liquid ammonia at low temperature , which one of the following does not occur ?

A solid substance 'A' is very hard and electrical insulator both in the solid state as well as in molten state. It has also very high melting point. Is the solid metal like silver or network solid like silicon carbide (SiC) ?

In ionic solids, the oppositely charged ions are closely packed in space and have strong electrostatic forces of attraction. These compound have high melting and boiling points and are poor conductors of electricity in the solid state. (i) Why are ionic solids poor conductros of electricity ? (ii) What happens to electrical conductivity when these are dissolved in water ?