Law of Gaseous volumes and Avogadro law
Law of Gaseous volumes

source : ncerthelp.com

Law of Gaseous volumes

source :slideplayer.com

Law of gaseous volumes-

This law was given by Gay Lussac. According to this law,

” When gases combine they do so in volumes which bear a simple ratio to each other and also to the product formed provided all gases are measured under similar conditions of temperature and pressure . “

Ex.1 –

H2      +        Cl2          =     2HCl

1 Vol.              1 vol.               2 vol.

Ratio  1 : 1 : 2

Ex.2-

2H2      +        O2          =     2H2O

2 Vol.              1 vol.               2 vol.

Ratio  2 : 1 : 2

Ex.3-

N2      +        3H2          =     2 NH3

1 Vol.              3 vol.               2 vol.

Ratio  1 : 3 : 2

Question ) 8.0 litre of H2 and 6.0 litre of Cl2 are allowed to react to maximum possible extent . Find out volume of reaction mixture . Suppose pressure and temperature remains constant through out the experiment.

Solution )

   H2                +          Cl2         ——->        2 HCl

Volume before reaction        8 litre                        6 litre                              0

Volume  after  reaction        2 litre                        0 litre                              12 litre

Total volume after reaction = volume of H2 left + volume of HCl formed = 2 + 12

Volume of reaction mixture = 14 litre Ans.

Avogadro’s Law-

According to this law,

“Equal volumes of gases under similar conditions of pressure and temperatures possess equal number of moles or molecules.”

∝ n         at constant pressure and temperature

∝ N         at constant pressure and temperature

n is  number of moles  and N is  number of  molecules of gases in volume ‘V’ at pressure ‘P’ and temperature ‘T’.

” At one atmosphere  pressure and 00C or 273 K , one mole of gas contains 6.023 x 10 23 ( avogadro’s number ) molecules of gas. “