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The vapour pressure of a certain liquid ...

The vapour pressure of a certain liquid is given by the equation:
`Log_(10)P = 3.54595 - (313.7)/(T) +1.40655 log_(10)T` where P is the vapour pressure in mm and `T =` Kelvin Temperature. Determine the molar latent heat of vaporisation as a function of temperature. calculate the its value at `80K`.

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The correct Answer is:
`DeltaH = 1659.9` Cal. At `80 K, DeltaH = R[313.7 xx 2.303 +1.40655 T]`
`(d InP)/(dT) = (DeltaH)/(RT^(2))` ...(i)
`logP = 3.54595 - (313.7)/(T) +1.40655 logT`
`In P = 3.54595 xx 2.303 - (313.7)/(T) xx 2.303 +1.40655 In T`
`(d In P)/(dT) = (313.7 xx 2.303)/(T^(2)) +(1.40655)/(T)` ...(ii)
Compairing equation (i) & (ii)
`DeltaH = R[313.7 xx 2.303 +1.40655 T]`
at `T = 80 K`
`DeltaH = 1659.9 Cal`.
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