JEE · NEET Previous Year Question
Given below are two statements:
Statement I: Upon heating a borax bead dipped in cupric sulphate in a luminous flame, the colour of the bead becomes green.
Statement II : The green colour observed is due to the formation of copper(I) metaborate. In the light of the above statements, choose the most appropriate answer from the options given below :
Topic: JEE PYQ
Answer: C. Full step-by-step solution below.
- ABoth Statement I and Statement II are true
- BStatement I is true but Statement II is false
- CBoth Statement I and Statement II are false
- DStatement I is false but Statement II is true
Correct answer: C
Solution
(c)(Borax Bead Test)
On treatment with metal salt, boric anhydride forms me tab orate of the metal which gives different colours in oxidising and reducing flame.
For example, in the case of copper sulphate, following reactions occur.
Two reactions may take place in reducing flame (Luminous flame)
(i) The blue-green Cu is reduced to colourless cuprous metaborate as :
2Cu + + C
+ + CO
(ii) Cupric metaborate may be reduced to metallic copper and bead appears red opaque.
2Cu + + 2C 2Cu + + 2CO
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