First slide

A certain salt (X) gives the following tests

(i) Its aqueous solution is alkaline to litmus.

(ii) On strongly heating it swells to give a glassy bead.

(iii) When concentrated sulphuric acid is added to a hot concentrated solution of (X), crystals of H3BO3 separate out. Identify the colour of these crystals.


X  is borax, Na2B4O7.10H2O (i)  Na2B4O7  + 7H2O    2NaOH(Strong Base)  + 4H3BO3(Weak acid)

Due to presence of NaOH, the aqueous solution is alkaline to litmus.

(ii) Na2B4O7.10H2O  swellsHeat   Na2B4O7  +  10H2O   2NaBO2   +   B2O3Glassy bead (iii) Na2B4O7 + H2SO4 + 5H2O   Na2SO4  +  4H3BO3White crystals

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