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The energy produced by the de`-`excitation of `(1)/(1000)` moles of `H -` atoms from `1^(st)` excited to ground state is supplied to `2` moles of an ideal gas. `10` litres of that gas at `27^(@)C` are allow to expand reversibly & isothermally. The final volume fo the gas will beA. `15l`B. `- 20l`C. `- 25l`D. `- 30l` |
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Answer» Correct Answer - B `DE = -2.18 xx 10^(-18) [1 - (1)/(4)]` `= -2.18 xx 10^(-18) xx (3)/(4)` J/ atom `= -2.18 xx 10^(-18) xx (3)/(4) xx 6.022 xx 10^(20)` Jouls for `(1)/(100)` moles `= -2.18 xx (3)/(4) xx 6.022 xx 10^(2)J` `= -3940 J` Now for isothermal expansion `DeltaU = 0` `:. dq = -dw` so `w = -2.303 nRT log. (v_(2))/(v_(1))` `- 39400 = -2.303 xx 2 xx 8.314 xx 300 xx "log" (v_(2))/(v_(1))` `"log"(v_(2))/(v_(1)) = (39400)/(11488.3)` `"log" (v_(2))/(10) = 0.3` or `(v_(2))/(10) = 2` `v_(2) = 20` litre |
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