Short Answer Type
Long Answer TypeExplain structures of diborane. Write the structures of diborane and explain the nature of bonding in it ?
How is borax prepared? Enlist the important uses of borax.
Preparation of borax:
(i) From tincal: The natural occurring borax (N2B4O7.10H2O) is called tincal. Tincal contains about 45% of boron. The natural tincal is dissolved in hot water and insoluble impurities are filtered off. The solution is concentrated and cooled when crystals of borax are obtained.
(ii) From colemanite: Te powdered mineral is heated with a slight excess of aqueous sodium carbonate.
The precipitates of calcium carbonate thus formed are removed by filtration. The filtrate (clear solution) is concentrated and cooled when crystals of borax separate out. Crystals of borax are separated and CO2 gas is passed through the mother liquor when sodium metaborate is also converted into borax. 
Sodium carbonate is again used.
Uses of borax:
It is used:
(i) In the manufacture of enamels, glazes and optical glass.
(ii) In the manufacture of soap and of drying oils.
(iii) As a flux in welding and soldering.
(iv) As an antiseptic.
(v) In the laboratory for borax bead test.
Short Answer TypeA certain salt X, gives the following results:
It aqueous solution is alkaline to litmus.
A certain salt X, gives the following results:
It swells up to a glassy material Y on strong heating.
A certain salt X, gives the following results:
When conc. H2SO4 is added to a hot solution of X, white crystals of an acid Z separate out.
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