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QJEEAdv19Ch519f: JEE Advanced 2019 Chemistry - Class 12 JEEAdv19Ch519f Solution: The green colour produced in the borax bead test of a chromium…

The green colour produced in the borax bead test of a chromium (III) salt is due to

Multiple Choice Options

  • A Cr2O3
  • B CrB
  • C Cr(BO2)3
  • D Cr2(B4O7)3

Step-by-Step Verified Solution

Borax bead test is performed only for coloured salt. Borax (sodium pyroborate), Na2B4O7.10H2O on heating gets fused and lose water of crystallisation. It swells up into fluffy white porous mass which melts into a colourless liquid which later form a clear transparent glassy bead consisting of boric anhydride and sodium metaborate.

JEE Advanced 2019 Paper 1 Offline Chemistry - d and f Block Elements Question 18 English Explanation 1

Boric anhydride is non-volatile. When it react with Cr(III) salt then deep green complex is formed.

JEE Advanced 2019 Paper 1 Offline Chemistry - d and f Block Elements Question 18 English Explanation 2

Hence, option (c) is correct.

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