Dulong and Petit’s law

According to Dulong and Petit’s law, At ordinary temperature the atomic heat of a solid element i.e., the product of atomic weight and specific heat of an element is a constant and its value is nearly 6.4

i.e., Atomic weight of an element 

So by obtaining the specific heat of an element its approximate atomic weight can be determined.

Now, this approximate atomic weight is divided by the experimental equivalent weight to obtain the valency of the element.


The nearest whole number is taken as the valency.

Exact atomic weight of the element= Equivalent weight x Valency.

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