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NEET Exam Model Paper 1

Question : 150 of 180

Marks: +1, -0

Borax bead test is not given by

Solution:

Only coloured salts on heating with the glassy borax bead form coloured metaborates in oxidising flame.

\mathrm{Na_2B_4O_7}\cdot 10\mathrm{H_2O}\xrightarrow[]{ \Delta }

\mathrm{Na_2B_4O_7}\xrightarrow[]{ \Delta }\underset{\text{Glassy bead}}{\mathrm{2NaBO_2+B_2O_3}}

Coloured salt

+\mathrm{B_2O_3}\rightarrow

Coloured metaborate Sodium salts are colourless and hence do not give a positive test.

Chromium - Green

Iron - Green

Cobalt - Blue

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