FeS + 6 HNO3 → 3 H2O + 3 NO2 + S + Fe(NO3)3
This is an oxidation-reduction (redox) reaction:
S-II - 2 e- → S0 (oxidation)
3 NV + 3 e- → 3 NIV (reduction)
FeII - 1 e- → FeIII (oxidation)
FeS is a reducing agent, HNO3 is an oxidizing agent, FeS is a reducing agent.
Reactants:
- FeS
- HNO3 – Nitric acid
- Other names: Aqua fortis , Spirit of niter , Eau forte
- Appearance: Colorless, yellow or red fuming liquid ; Colourless-to-yellow liquid with pungent odour ; Colorless, yellow, or red, fuming liquid with an acrid, suffocating odor. [Note: Often used in an aqueous solution. Fuming nitric acid is concentrated nitric acid that contains dissolved nitrogen dioxide.]
Products:
- H2O – Water, oxidane
- NO2 – Nitrogen dioxide
- Other names: Nitrogen(IV) oxide , Deutoxide of nitrogen , Nitrogen peroxide
- Appearance: Brown gas ; Reddish-brown gas or brown or yellow liquid with pungent odour ; Yellowish-brown liquid or reddish-brown gas (above 70°F) with a pungent, acrid odor. [Note: In solid form (below 15°F) it is found structurally as N2O4.]
- S
- Fe(NO3)3 – Iron(III) nitrate