Question

Assertion (A) : Silica is soluble in $HF$.
Reason ( R ): $SiO _{2}+4 HF \longrightarrow SiF _{4}+2 H _{2} O$
$SiF _{4}+2 HF \longrightarrow H _{2} SiF _{6}$

• A. A and R both are correct and R is the correct explanation of A.
• B. A and R both are correct but R is not the correct explanation of A.
• C. A and R both are incorrect.
• D. A is correct while R is incorrect.

Answer 1

Answer: (B)

Silica is soluble in $HF$.
$SiO _{2}$ reacts with HF to give $SiF _{4}$ if $HF$ is present in excess it gives $H _{2} SiF _{6}$.
$SiO _{2}+4 HF \longrightarrow SiF _{4}+2 H _{2} O $
$SiF _{4}+2 HF \longrightarrow H _{2} SiF _{6}$
hydrofluoro silicic acid