Question

A minute quantity of cupric salt is heated on borax bead in reducing flame of bunsen burner, the color of bead after cooling will be:
A.Blue
B.Brown red
C.Colorless
D.Green

Answer 1

Hint:Borax bead test is a part of the qualitative inorganic analysis to test for the presence of few metals. In this test different metals give different colors but this method is not applicable for all metals .

Complete step by step answer:
In question given information is the process for detecting $cu$metal with help of borax bead test
When we subject a cupric salt on borax bead test two reactions may take place in the reducing flame
The blue \[Cu{\left( {B{O_2}} \right)_2}\]is reduced to colorless cuprous metaborate
Or
Cupric metaborate may be reduced to metallic copper and the bead appears red and opaque
But this are the characteristics of $NaBr$
Bead appears red and opaque Hence answer for the question is option “B”.

Additional information:
BORAX BEAD TEST
The mixture of meta borate $NaB{O_2}$ and boric acid ${B_2}{O_3}$ Is used in borax test
$CuO + {B_2}{O_3} \to Cu{(B{O_2})_2}$
On heating in reducing flame we get $CuB{O_2}$ which is subjected to cooling we get green color
Sodium ions are not colored. Therefore, they do not give a borax bead test. This test is given by colored salts.
Borax bead test is generally used to detect transition metals because in transition all metals give colored compounds.
Borax bead test is a test for the presence of certain metals by observing the colors given to a bead of borax in a loop of platinum wire held in the oxidizing and reducing parts of a bunsen burner flame
A cobalt salt gives deep blue color result
A copper salt gives sky blue and red color in oxidizing and reducing parts respectively.

Note:
Whenever a colored salt-containing cation is heated with a borax bead on a platinum wire, it forms metaborates .This test is called the borax bead test.