Question

Ageous solution of a sqalt (Y) is alkline to litmas On strong heating it swells-up to give a glassy material .When cone `H_(2)SO_(4)` in added to a hot concentrated solution of (Y) white crystals of a weak acid sepurate out .Hence , the compound (Y) is
A. `Na_(2)SO_(4).10H_(2)O`
B. `Ca_(2)P_(4)O_(11).10H_(2)O`
C. `Na_(2)B_(6)O_(11)`
D. `Na_(2)B_(4)O_(7).10H_(2)O`

Answer 1

Correct Answer - d
`Na_(2)B_(4)O_(7)+7H_(2)Orarr ubrace(underset("Stronge base")(2NaOH)+underset("Weak acid")(4H_(3)BO_(3)))_("Alkaline")`
`Na_(2)B_(4)O_(7)+7H_(2)O overset(Delta)rarrubrace(2NaBO_(2)+B_(2)O_(3))_("Glassy-bead")`
`underset(("White crystals"))(Na_(2)B_(4)O_(7))+H_(2)SO_(4)+5H_(2)O rarr Na_(2) SO_(4) +4H_(3)BO_(3)`