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How does kinetic throry justify Avogadro's hypothesis and show that Avogadro Number in different gases is same?

Answer»

Solution :Avogadro.s law or Avogadro.s hypothesis: It STATES that "equal VOLUMES of all gases under similar conditions of temperature and pressure contain equal number of molecules".
Consider two gases distinguished by subscripts 1 and 2.
LET
`m_(1)` and `m_(2)` =masses of molecules of 1 and 2 respectively.
`N_(1) and N_(2)` = no. of molecules of 1 and 2 respectively
`P_(1) and P_(2)` = pressure of 1 and 3 respectively
`V_(1) and V_(2)` = volumes of 1 and 2 respectively.
`P_(1) V_(1) = 1/3 m_(1)N_(1) bar(V_(1)^(2)) and P_(2) V_(2) = 1/3 m_(2)N_(2) bar(V_(2)^(2))`
For equal volumes at the same pressure,
`P_(1) V_(1) = P_(2) V_(2)`
`:. 1/3 m_(1)N_(1) bar(V_(1)^(2)) =1/3 m_(2)N_(2) bar(V_(2)^(2))`_______ (1)
If the gases are at the same temperature the average kinetic energies of their molecules are equal.
i.e., `1/2 m_(1)bar(V_(1)^(2)) = 1/2 m_(2)bar(V_(1)^(2)) implies m_(1) bar(V_(1)^(2)) = m_(2) bar(V_(1)^(2))`
`:.` equation (1) becomes : `N_(1) = N_(2)`
Hence, equal volumes of all gases under similar conditions of temperature and pressure have the same number of molecules.


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