Question

mention the method of determining the mass of atom and molecules​

Answer 1

Answer:

Explanation:

(i) Dulong and Pettit's method: According to Dulong and Pettit's law

Atomic mass Specific heat = 6.4 (approx.)

Atomic mass (approx.) =  6.4/Specific heat (in cals.)

This law is applicable to solid elements only except Be, B, C and Si because their specific heat is variable with temperature.

Atomic mass = Equivalent mass × Valency

Valency = (Approximate atomic mass/Equivalent mass)

(ii) Vapour density method: It is suitable for elements whose chlorides are volatile.

Valency of the element = Molecular mass of chloride/Equivalent mass of chloride    

= 2 × Vapour density of chloride/Equivalent mass of metal + 35.5

Atomic mass = Equivalent mass of metal Valency

(iii) Specific heat method: It is suitable only for gases. The two types of specific heats of gases are CP (at constant pressure) and  (at constant volume). Their ratio is known as g whose value is constant (1.66 for monoatomic, 1.40 for diatomic and 1.33 for triatomic gases).

         Atomic mass of a gaseous element = Molecular mass/Atomicity

(iv) Isomorphism method: It is based on law of isomorphism which states that compounds having identical crystal structure have similar constitution and chemical formulae.

Example: K2 SO4, K2 CrO4 and SeO4

(valency of S, Cr, Se = 6),

ZnSo4. 7H2O, MgSO4 7H2O, FeSO4 7H2O

(valency of Zn, Mg, Fe = 2).