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What amount of work is performed when 1 kg of water turns into steam at 100^(@)C ? How much energy is spent to break the bonds between the molecules? |
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Answer» Solution :Since evaporation takes place at a constant pressure, `W= p(v_(0)^("vap")-v_(0)^("liq"))` where `v_(0)=1//rho` is the specific volume, i.e. the volume of 1 kg of the SUBSTANCE. Hence `W=p((1)/(rho_("vap"))(1)/(rho_(11Q)))` The density of steam at `100^(@)C` may be found from Table 35.1 (see35.3). Since the specific volume of VA pour is almost a thousand times gronter than the specifio volume of LIQUID, it follows with better than 1% accuracy that `W=p//rho_(vap)` The ENERGY spent on breaking the bonds between the molecules can be found from the first law of thermodynamics: `Delta = L - W` where L is the specific heat of evaporation. |
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