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Borax [Na(2)B(4)O(7).10H(2)O] when heate...

Borax `[Na_(2)B_(4)O_(7).10H_(2)O]` when heated on platinum loop it gives a dark transparent glass like bead. The hot bead is dipped in the salt till it reacts with transition metal oxide. It produces characteristic bead of meta borate.
`{:(" Colour of the bead"," lon"),("(a) Blue green or light blue",Cu^(+2)),("(b) Yellow",Fe^(+2)or Fe^(+3)),("(c) Green",Cr^(+3)),("(d) Violet",Mn^(+2)),("(e) Dark blue",Co^(+2)),("(f) Brown",Ni^(+2)):}`
Glassy bead is of

A

`B_(2)O_(3)+NaBO_(2)`

B

`Na_(3)BO_(3)`

C

`Na_(2)B_(4)O_(7)`

D

`SiO_(2)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question regarding the composition of the glassy bead formed from borax when heated, we can follow these steps: ### Step-by-Step Solution: 1. **Understanding Borax**: - Borax is chemically represented as `Na₂B₄O₇·10H₂O`. It contains sodium, boron, oxygen, and water of crystallization. 2. **Heating Borax**: - When borax is heated, it loses its water of crystallization. The reaction can be represented as: \[ \text{Na}_2\text{B}_4\text{O}_7 \cdot 10\text{H}_2\text{O} \rightarrow \text{Na}_2\text{B}_4\text{O}_7 + 10\text{H}_2\text{O} \] - This results in the formation of anhydrous borax. 3. **Formation of Glassy Bead**: - Upon further heating, the anhydrous borax decomposes to form a transparent, glassy bead. This bead is primarily composed of sodium metaborate (`NaBO₂`) and boric anhydride (`B₂O₃`). 4. **Chemical Composition of the Bead**: - The glassy bead can be represented as: \[ \text{NaBO}_2 + \text{B}_2\text{O}_3 \] - This combination results in a glassy structure that is characteristic of the borax bead test. 5. **Conclusion**: - The glassy bead formed from borax when heated is made up of sodium metaborate and boric anhydride. Therefore, the answer to the question is that the glassy bead is of sodium metaborate. ### Final Answer: The glassy bead is made up of **Sodium Metaborate** and **Boric Anhydride**. ---
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Borax [Na_(2)B_(4)O_(7).10H_(2)O] when heated on platinum loop it gives a dark transparent glass like bead. The hot bead is dipped in the salt till it reacts with transition metal oxide. It produces characteristic bead of meta borate. {:(" Colour of the bead"," lon"),("(a) Blue green or light blue",Cu^(+2)),("(b) Yellow",Fe^(+2)or Fe^(+3)),("(c) Green",Cr^(+3)),("(d) Violet",Mn^(+2)),("(e) Dark blue",Co^(+2)),("(f) Brown",Ni^(+2)):} The colour of bead Ni(BO_(2))_(2) is

Borax [Na_(2)B_(4)O_(7).10H_(2)O] when heated on platinum loop it gives a dark transparent glass like bead. The hot bead is dipped in the salt till it reacts with transition metal oxide. It produces characteristic bead of meta borate. {:(" Colour of the bead"," lon"),("(a) Blue green or light blue",Cu^(+2)),("(b) Yellow",Fe^(+2)or Fe^(+3)),("(c) Green",Cr^(+3)),("(d) Violet",Mn^(+2)),("(e) Dark blue",Co^(+2)),("(f) Brown",Ni^(+2)):} The flame used in Borax Bead test is

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