Chemical reactions

Reaction of hydrogen with acids

Hydrogen, H2, does not react with dilute acids.

Reaction of hydrogen with air

Hydrogen, H2, does react with oxygen, O2, unless ignited with a flame or a spark (and the mixture is the right ratio). The reaction is a fire or explosion, depending on the conditions, with a characteristic reddish flame.

2 H2(g) + O2(g) 2 H2O(g)

Nitrogen can be brought to react with hydrogen. This is called the Haber process [5]:

N2(g) + 3 H2(g)
400-500 °C
Fe catalyst

High pressure
2 NH3(g)

Reaction of hydrogen with bases

Hydrogen, H2, does not react with dilute bases.

Reaction of hydrogen with halogens

Hydrogen, H2, reacts with halogens, forming hydrogen halides. The reactions are slow at room temperature, except for fluorine and increases in speed with increasing temperatures. The reaction with fluorine is fast, even at room temperature. Under some conditions, the reactions with fluorine and chlorine can be explosive [5].

H2(g) + F2(g) 2 HF(g)
H2(g) + Cl2(g) 2 HCl(g)
H2(g) + Br2(g) 2 HBr(g)
H2(g) + I2(g) 2 HI(g)

Reaction of hydrogen with metals/metal ions

Hydrogen reacts with alkali metals and calcium, strontium and barium, forming hydrides [5]:

2 Li(s) + H2(g) 2 LiH(s)
2 Na(s) + H2(g) 2 NaH(s)
2 K(s) + H2(g) 2 KH(s)
2 Rb(s) + H2(g) 2 RbH(s)
2 Cs(s) + H2(g) 2 CsH(s)
Ca(s) + H2(g) CaH2(s)
Sr(s) + H2(g) SrH2(s)
Ba(s) + H2(g) BaH2(s)

Cd usually does not react with H2(g). At 450 °C H2 is adsorbed in the metal. When the metal has reached max. adsorption the temperature will increase and Cd reacts with H2 [4].

Cd(s) + H2(g) CdH(s) + H·

Hydrogen does not react with gold, platinum and tungsten, but is dissolved in the metal instead [5]

Hydrogen reduces some metal oxides [5]:

Fe3O4(s) + 4 H2(g) 3 Fe(s) + 4 H2O(g)
MnO4(s) H2(g) MnO(s) + H2O(g)

Reaction of hydrogen with sulfur

Sulfur reacts with hydrogen, forming hydrogen sulfide [5]:

S8(s) + 8 H2(g) 8 H2S(g)

Reaction of hydrogen with water

Hydrogen does not react with water, but it is slightly soluble in water (1.6 mg/l (20 °C) [2])