Physical properties: colorless gas, with rotten egg smell, soluble in water (2.6 volume), heavier than air and toxic.

Chemical properties:

1) easy to decompose when heated: H2S = H2+S.

2) Flammable:

Full combustion occurs when the air is sufficient: 2H2S+3O2=2SO2+2H2O (condition: ignition).

Insufficient air leads to insufficient combustion: 2H2S+O2=2S+2H2O.

3) Reducibility: Sulfur in hydrogen sulfide has the lowest price, strong reducibility and easy oxidation, so it is a strong reducing agent.

2H2S+SO2=2H2O+3S

H2S+Cl2=2HCl+S(Br2 and I2 have similar reactions).

H2S+H2SO4 (concentrated) =S↓+SO2+2H2O (H2S cannot be dried with concentrated sulfuric acid).

4) Acidity: The aqueous solution of hydrogen sulfide is called bisulfate, which is a weak acid with strong reducibility.

Strong reducibility: 2H2S+O2=2S (precipitation) +2H2O (this reaction shows that nonmetal of S is weaker than O).

Acidity: H2S+2NaOH=Na2S+2H2O.