Question

Borax bead test is given by:
This question has multiple correct options:

a.) An aluminium salt
b.) A cobalt salt
c.) A copper salt
d.) A nickelate salt

Answer 1

Hint: Borax bead test is used to identify the present metal in a given mineral or salt. The chemical formula of borax is ${ Na }_{ 2 }{ B }_{ 4 }{ O }_{ 7 }{ .10H }_{ 2 }{ O }$. When heated under the Bunsen flame, it loses its water of crystallization and forms a colorless transparent glassy bead called a borax bead which is a mixture of sodium metaborate and boric anhydride.

Complete answer:
Borax bead test: The preparation of borax bead is given as:
${ Na }_{ 2 }{ B }_{ 4 }{ O }_{ 7 }{ .10H }_{ 2 }{ O\rightarrow { Na }_{ 2 } }{ B }_{ 4 }{ O }_{ 7 }{ \rightarrow 2NaB{ O }_{ 2 }+{ B }_{ 2 } }{ O }_{ 3 }$
This mixture of sodium metaborate and boric anhydride is called a borax bead. It is used to test the presence of certain metals.
Borax bead test is a test for the presence of specific metals by observing the colors given to a bead of borax in a circle of platinum wire held in the oxidizing and reducing parts of a bunsen burner fire.
An aluminum salt gives the dry result(it doesn’t give borax bead test).
A cobalt salt gives a dark blue color result.
A copper salt gives sky blue and red color in oxidizing and reducing parts individually.
A nickelate salt gives yellow earthy colored and grey color in oxidizing and reducing parts individually.
So, just aluminium salt don't give borax bead test all the others gives borax bead test
Hence, options B, C, and D are correct.
Note: The possibility to make a mistake is that the metaborates that are formed color the bead. But this is a preliminary test and the results observed are further confirmed by chemical analysis.