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In the vicinity of the triple point the saturated vapour pressure p of carbon dioxide depends on temperature T as log p = 1 - b//T, where a and b are constants. If p is expressed in atomspheres, then for the sublimation processa = 9.05 and b = 1.80 kK, and for the vaporization process a = 6.78 and b = 1.31 kK. Find : (a) temperature and pressure at the triple point , (b) the values of the specific latent heats of sublimation, vaporization, and melting in the vicinity of the triple point. |
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Answer» Solution :(a) The equations of the transition LINES are `log p = 9.05 - (1800)/(T)` : Solid GAS =`6.78 - (1310)/(T)` : Liquid gas At the triple point they intersect. Thus `2.27 = (490)/(T_(tr))` or `T_(tr) = (490)/(2.27) = 216 K` corresponding `p_(t r)` is 5.14 atmosphere In the formula `log p = a - (b)/(T)`, we compare `b` with the corresponding term in the equation in `2.210`. Then `1n p = 1 XX 2.303 - (2.303 b)/(T)` So, `2.303 = (Mq)/( R)` or `q_("SUBLIMATION") = (2.303 xx 1800 xx 8.31)/(44) = 783 J//gm` `q_("liquid-gas") = (2.303 xx 1310 xx 8.31)/(44) = 570 J//gm` Finally `q_("solid - liquid") = 213 J//gm` on subtraction. |
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