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