Physical properties of H₂

1. It is colourless.
2. It is odourless.
3. It is tasteless.
4. Its vapor density = 1 (lighter than air).
5. It is non – poisonous.
6. It is solubility in H₂O is very low.

Chemical Properties –

1. It is chemicaly inert at room temperature.

• Its chemical nature depends upon Bond dissocitaion energy of ( H – H)bond.
• The Bond dissociation energy is high because of comparable sizes . Due to small size ,it requires high temperature to break the bond that is 2000k or more than that . At 5000k  it gets 95.5% dissociates.
• Although the Bond dissociation energy is high for H – H, but still Hydrogen is reactive . It has  only 1 valence electron so, it combines or we can say react to attain 2electrons  is its  

               It Can attain stability by :

• Burning in presence of O₂ – It reacts with oxygen to form water and the reaction is exothermic.

               2H₂      + O₂    –> H₂O + Energy               

            Hydrogen Oxygen     Water   

• Reaction with halogens : it react with halogens to form respectives halides as shown below :

            H₂      +    Cl₂    –> 2HCl  

        Hydrogen   Chlorine     HydrogenChloride

• Reaction with N-metal –

It reacts with many non metals to form hydrides. Like with sulphur it forms sulphides ,with Oxygen it forms oxides ,with Flourine it forms flourides etc  as shown below :

 1.  H₂             + S          –> H₂S

      Hydrogen  Sulphur  HydrogenSulphide

2.  2H₂      + O₂    –> H₂O                

   Hydrogen Oxygen     Water

3. H₂          +   F₂  –>   HF

   Hydrogen    Fluroide   HydrogenFluroide

4. N₂   + 3H₂   –>  2NH₃(Haber’s Process) (In the presence of catalyst) 

 Nitrogen   Hydrogen              Ammonia

• H₂ as Reducing agent –

As we have discussed in the introduction of hydrogen ,that it act as a reduvcing agent so, here we have certains examples as given below :

•  Hydrogenation of Oils –

            It is the Process of converting vegetable oil into vanaspati ghee by adding H₂ in presence of catalyst nickel.

Vegetable Oil —> Vanaspati Ghee(In presence of Ni)

Uses of H₂ –

• It is used as rocket fuel because of its high calorific value.
• OxyHydrogenflame is used for welding.
• It helps in synthesis of NH₃(ammonia) , HNO₃ (niric acid),HCl(hydrochloric acid) etc.
• It helps in the synthesis of vanspati ghee.
• It is a reducing agent .