Reaction of ruthenium with air
Ruthenium reacts very little oxygen, O2, under normal conditions. If heated, ruthenium is oxidized to Ru(IV) oxide:
Ru(s) + O2(g) RuO2(s)
Reaction of ruthenium with halogens
Ruthenium will react with excess F2, forming ruthenium(VI) fluoride, RuF6.
Ru(s) + 3 F2(g) RuF6(s) [dark brown]
When heating to 330 °C, ruthenium will react with chlorine, Cl2, in the presence of carbon monoxide, CO, forming a dark brown ruthenium(III) chloride, RuCl3. Additional heating of the material, in the presence of Cl2, gives a black form of ruthenium(III) chloride.
2 Ru(s) + 3 Cl2(g) 2 RuCl3(s)
Reaction of ruthenium with water
Ruthenium reacts with water :
Ru2+(aq) + 2 H2O(l) RuO2(s) + 4 H+(aq) + 2 e− E° = -1.120 V
RuO2(s) + 2 H2O(l) RuO4(s) + 4 H+(aq) + 4 e− E° = -1.387 V
Ru2+(aq) + 4 H2O(l) RuO42−(aq) + 8 H+(aq) + 4 e− E° = -1.563 V
Ru2+(aq) + 4 H2O(l) RuO4−(aq) + 8 H+(aq) + 5 e− E° = -1.368 V