$5\mathrm{.}5$ Problems

$$ Problem $1$: What is the work done if $2$ kg of air undergoes a reversible change in a well$-$insulated piston$-$cylinder system from $100$ kPa and $50C$ to $350$ kPa $?$ For air use: $c_p=1\mathrm{.}007kJk{g}^{-1}{K}^{-1},c_{?}$

$u=0\mathrm{.}7197kJk{g}^{-1}{K}^{-1},k=1\mathrm{.}38.$

Problem $2$: What is the quantity of heat transferred if $2$ kg of water undergoes a reversible change from $10$ bar and a quality of $0\mathrm{.}1$ to $250C$ in a rigid container?

Problem $3$: A rigid tank contains $0\mathrm{.}25$ kg of water with a quality of $0\mathrm{.}8$ at $2$ bar. The system is then heated to $350C.$ Calculate:

a$)$ The initial temperature of the system.

b$)$ The final pressure of the system and the amount of heat that must be added.

c$)$ If the system is then allowed to cool until the tank contains only saturated steam, calculate the final pressure and temperature of the system, and the amount of heat removed.

The answers are

$1)-191\mathrm{.}61$ KJ

$2)1470\mathrm{.}08$ KJ

$3)$

A$)120\mathrm{.}21$ C

B$)4\mathrm{.}03$ Bar, $190\mathrm{.}05$ KJ

C$)2\mathrm{.}54$ bar,$127\mathrm{.}92$ C$,-86\mathrm{.}76$ KJ

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