Phase Change Question

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Phase Change Question

Postby Connie2I » Fri Jan 19, 2018 6:32 pm

Was there a formula to use when calculating a phase change like vaporization or anything? In the notes it said something like deltaH of vaporization = H vapor - H liquid, but the solutions manual for problem 8.37 seems to use q and moles instead so I wasn't sure

Lisa Tang 1C
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Re: Phase Change Question

Postby Lisa Tang 1C » Fri Jan 19, 2018 7:51 pm

For 8.37, you consider the units that enthalpy is reported in (kJ/mol). So, you should divide the heat (measured in kJ) by moles of the substance to find delta H of vaporization.

Charles Ang 1E
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Re: Phase Change Question

Postby Charles Ang 1E » Sat Jan 20, 2018 4:33 pm

Hvap = kJ/moles is what the book gives as the value of enthalpy of vaporization. For the question, we are given a value in kJ and in moles. Just put those value into the formula to get the answer.

Rakhi Ratanjee 1D
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Re: Phase Change Question

Postby Rakhi Ratanjee 1D » Sat Jan 20, 2018 4:51 pm

Generally, when you have to find the energy required for a phase change, use the formula Energy (q) = (mass of sample)*(heat of fusion/vaporization of substance in J/g)

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