Hydrogen

Hydrogen, H₂, does not react with dilute acids.

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) 2 NH₃(g)

Hydrogen, H₂, does not react with dilute bases.

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)

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)

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

S₈(s) + 8 H₂(g) 8 H₂S(g)

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