Question

i.(A) `overset(Delta)to ` glassy traparent beat (B) on platinum wire
(B) `+ CuSO_(4) rarr ` coloured bead(C )
ii `underset((D))((A))+conc. H_(2)SO_(4)+CH_(3)CH_(2)OH overset("ignite")rarr` green flame
iv.Aqueous solution (A) is alkline
Identify (B) .
A. `NaPO_(3)`
B. `NaBO_(2)`
C. `NaBO_(2) + B_(2)O_(3)`
D. None of these

Answer 1

Correct Answer - c
i.(A) Forms glassy transpatent beat which is characteristic property of borax
`rArr(A)` is borax `(Na_(2)B_(4)O_(7).10H_(2)O)`
`Na_(2)B_(4)O_(3)10H_(2)O overset(Delta) to (NaBO_(2) + B_(2)O_(3))/((B) "Glassy bead") + 10H_(2)O`
`B_(2)O_(3) + CuSO_(4) overset(Delta)to underset("Coloured bead(C))(Cu(BO_(2))_(2) +SO_(3)uarr`
ii `Na_(2)B_(4)O_(3) + H_(2)SO_(4) + 5H_(2)O rarr NA_(2)SO_(4) + 2H_(3)BO_(3)`
`H_(#)BO_(3) +3C_(2)H_(5)OH rarr underset("Green flame" (on ignition")(D))((C_(2)H_(5))_(3)BO_(3)+3H_(2)O)`
`Na_(2)B_(4)O_(7)+5H_(2)O rarr underset("Weak acid")(2H_(3)BO_(3))+2Na[B(OH)_(4)]`
`Na[B(OH)_(4)]` reacts with acid `(HCI)` hence aqueous solution of (A) is alkaline.