1. 2Ag(s) + H2S(g) -----> Ag2S(s) + H2(g)
Corrosion of tarnishing of silver is an example of " Displacement reaction"
Here we have oxidation reaction, because when silver is exposed to air, a layer of silver sulfide is formed on the surface. The non-metal sulphur leaves H2S and deposited on the surface of silver.
2. 2 NaHCO3(aq) + H2SO4(l) -> Na2SO4(aq) + 2 H2O(l) + 2 CO2(g)
In Soda acid fire extinguisher there is " Decomposition reaction".
This is a decomposition reaction, as here,
NaHCO3 decomposes: 2NaHCO3 → Na2CO3 + H2O + CO2
The sodium carbonate further decomposes: Na2CO3 → Na2O + CO2 .