The gas evolved on heating \(\mathrm{CaF_2}\) and \(\mathrm{SiO_2}\) with concentrated \(\mathrm{H_2SO_4}\), on hydrolysis gives a white gelatinous precipitate. The precipitate is:
Show Hint
- Silicic acid
- Calcium fluorosilicate
- Hydrofluorosilicic acid
- Silica gel
The Correct Option is A
Solution and Explanation
\(\mathrm{SiO_2+4HF\to SiF_4\uparrow+2H_2O}\)
Hydrolysis: \(\mathrm{3SiF_4+4H_2O\to H_4SiO_4\downarrow+2H_2SiF_6}\)
The white gelatinous precipitate is silicic acid, \(\mathrm{H_4SiO_4}\) (orthosilicic acid); \(\mathrm{H_2SiF_6}\) stays in solution.
Answer: (1) Silicic acid
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