(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Calculate the change in the enthalpy of argon, in KJ/kg, when it is cooled from 100 to 25 °C.

2. Relevant equations

[tex]\Delta h = c_{p} \Delta T[/tex]

Where [itex]\Delta h[/itex] is the change in enthalpy, [itex]c_{p}[/itex] is the specific heat, and [itex]\Delta T[/itex] is the change in temperature.

3. The attempt at a solution

[tex]\Delta h = c_{p,avg} \Delta T[/tex]

[tex]\Delta h_{argon} = c_{p,avg} \Delta T=\left (.5203\frac{kJ}{kg\cdot C} \right )\left (100 C-25C \right )=39.0\frac{kJ}{kg}[/tex]

My book has a table at the back that is labeledIdeal-gas specific heats of various common gases at 300 K. The answer given to this question uses the c_{p}values listed in this table. This makes no sense to me as [itex]c_{p,avg}[/itex] would be (c_{p}at T_{1}+ c_{p}at T_{2})/2.

How can the book use the values from a table where c_{p}values are given for temperatureat 300 K?

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# Homework Help: Enthalpy change - Using tables to find specific heat

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