What happens when?
(a) Red lead is treated with nitric acid.
(b) NaOH solution is added to `SnCl_(2)` solution.
(c) Silica is heated with `CaF_(2)` and conc. `H_(2)SO_(4)`

Explanation

(a) `Pb_(3)O_(4)to2PbO+PbO_(2)`
`( [PbO + 2HNO_(3)to Pb(NO_(3))_(2) +H_(2)O]xx2)/(Pb_(3)O_(4) + 4HNO_(3)to2Pb(NO_(3))_(2) +PbO_(2) +2H_(2)O)`
(b)` SnCl_(2) + 2NaOHto Sn(OH)_(2)+2NaCI`
`(Sn(OH)_(2) +2NaOHtoNa_(2)SnO_(2) +2H_(2)O)/(SnCl_(2) + 4NaOHtoSn(OH)_(2)+2NaCI)`
(c) `[CaF_(2)+H_(2)SO_(4)toCaSO_(4)+2HF]xx2`
`(SIO_(2)+4HFtoSIF_(4)+2H_(2)O)/(2CaF_(2) +SiO_(2)+2H_(2)to2CaSO_(4)+SIF_(4)+2H_(2)O)`