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Aqueous solution of a salt (Y) is alkali...

Aqueous solution of a salt (Y) is alkaline to litmus. On strong heating it swells-up to give a glassy material .When conc `H_(2)SO_(4)` in added to a hot concentrated solution of (Y) white crystals of a weak acid separate out .Hence , the compound (Y) is

A

`Na_(2)SO_(4).10H_(2)O`

B

`MgSO_(4).7H_(2)O`

C

`Na_(2)B_(6)O_(11)`

D

`Na_(2)B_(4)O_(7).10H_(2)O`

Text Solution

Verified by Experts

The correct Answer is:
D
x is Borax
`Na_(2)B_(4)O_(7).10H_(2)O`
`Na_(2)B_(4)O_(7) + 7H_(2)O rarr 2NaOH + 4H_(3)BO_(3)`
`Na_(2)B_(4)O_(4) rarr underset(ubrace("Glassy bead"))(2NaBO_(2) + B_(2)O_(3))`
`Na_(2)B_(4)O_(7) + H_(2)SO_(4) + 5H_(2)O rarr Na_(2)SO_(4) + 4H_(3)BO_(3)`
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