Reaction of carbon with acids
Graphite reacts with the oxidizing acid hot concentrated nitric acid to form mellitic acid, C6(COOH)6.
Reaction of carbon with air
Carbon, as graphite, burns, forming gaseous carbon oxides. Diamond, when heated to 600-800 °C, also burns, forming gaseous carbon oxides.
At sufficient amounts of O2, carbon forms CO2 (carbon dioxide). This is called complete combustion :
C(s) + O2(g) CO2(g)
At insufficient amounts of O2, carbon forms CO (carbon monoxide). This is called incomplete combustion :
2 C(s) + O2(g) 2 CO(g)
Reaction of carbon with calcium oxide
Carbon reacts with calcium oxide at high temperatures, forming calcium carbide :
3 C(s) + CaO(s) CaC2(s) + CO(g)
Reaction of carbon with halogens
Graphite reacts with fluorine, F2, (excess amount) at high temperatures, forming a mixture of CF4, C2F6 and C5F12.
C(s) + F2(g) CF4(g) + C2F6 + C5F12
At room temperatur, the reaction with fluorine result in a mixture called "graphite fluoride". This is a non-stoichiometric mixture with the formula CFx (0.68 < x < 1). The compound is black when x is low, silvery at x = 0.9 and colourless when x is around 1.
Reaction of carbon with sodium amide
Carbon reacts with sodium amide at 500-600 °C, forming sodium cyanide :
C(s) + NaNH2(g) NaCN(s) + H2(l)
Reaction of carbon with sulfur
Carbon reacts with sulfur at high temperatures, in the absense of oxygen, forming carbon disulfide :
C(s) + 2 S(s) CS2(g)
Reaction of carbon with water
Carbon, either as graphite or diamond, does not react with water under normal conditions.
At high temperatures, when water is blown through hot coke, carbon will react with water, forming a mixture of hydrogen (H2, 50%), carbon monoxide (CO, 40%), carbon dioxide (CO2, 5%), nitrogen and methane (N2 + CH4, 5%).
2 C(s) + 3 H2O(g) CO(g) + CO2(g) + 3 H2(g)