The gas evolved on heating CaF2 and SiO2 with concentrated H2SO4, which on hydrolysis gives a white gelatinous precipitate. The precipitate is:

Question

The gas evolved on heating CaF2 and SiO2 with concentrated H2SO4, which on hydrolysis gives a white gelatinous precipitate. The precipitate is: (A) Hydrofluorosilicic acid (B) Silica gel (C) Silicic acid (D) Calcium fluorosilicate

Tardigrade Admin · Accepted Answer

Reactions: H 2 SO 4+ CaF 2 arrow Ca ( HSO 4)2+ H 2 F 2 2 H 2 F 2+ SiO 2 arrow SiF 4+2 H 2 O SiF 4+ H 2 O arrow H 2[ SiF 6] H 2 SiF 6 is hydrofluorosilicic acid.

Q. The gas evolved on heating $C a F_{2}$ and $S i O_{2}$ with concentrated $H_{2} S O_{4}$ , which on hydrolysis gives a white gelatinous precipitate. The precipitate is:

Hydrofluorosilicic acid

Silica gel

Silicic acid

Calcium fluorosilicate

Reactions:
$H_{2} S O_{4} + C a F_{2} \to C a (H S O_{4})_{2} + H_{2} F_{2}$
$2 H_{2} F_{2} + S i O_{2} \to S i F_{4} + 2 H_{2} O$
$S i F_{4} + H_{2} O \to H_{2} [S i F_{6}]$
$H_{2} S i F_{6}$ is hydrofluorosilicic acid.

Q. The gas evolved on heating CaF2​ and SiO2​ with concentrated H2​SO4​, which on hydrolysis gives a white gelatinous precipitate. The precipitate is: