Question

The test of which of the following anions is not performed in a glass test tube?

• A. $F^{-}$
• B. ${AsO}_4^{3-}$
• C. ${PO}_4^{3-}$
• D. ${BO}_3^{3-}$

Answer 1

Answer: (A)

$F^{-}$

The test for fluoride ions is not performed in a glass test tube.
The fluoride ions attack silicates as well as silica as indicated in the following reactions.
$Si{O}_2+4F^{-}\to Si{F}_4+4O{H}^{-}$
$CaSi{O}_3+6F^{-}\to CaSi{F}_4+6O{H}^{-}$