Question

Which of the following imparts green colour to the burner flame?

• A. $B(OMe{)}_3$
• B. $Na(OMe)$
• C. $Al(OPR{)}_3$
• D. $Sn(OH{)}_2$

Answer 1

Answer: (A)

In the qualitative analysis of $B{O}_3^{3-}$ radical, mixture is heated with conc. $H_{2}S{O}_4$ and little alcohol when trialkyl borate is obtained. The vapours of trialkyl borate $B(OR{)}_3$ or $R_{3}B{O}_3$ burn with green edged flame.
$2B{O}_3^{3-}+3H_{2}S{O}_4⟶3S{O}_4^{2-}+2H_{3}B{O}_3$
$H_{3}B{O}_3+3ROH⟶\underset{\text{Trialkaly borate}}{R_{3}B{O}_3}+3H_{2}O$