Question

In a certain gas system,the pressure remains constant at 150 kpa even though 1000J of heat is added. The volume change is 1.8L. how much does the internal energy in joules of the system change.

Answer 1

Solution.

$p=150\sdot 10^3 Pa;$

$Q=1000J;$

$\Delta V=1.8L=1.8\sdot 10^{-3} m^3;$

$U -?$

$Q=U+A;$

$A=p\Delta V;$

$A=150\sdot 10^3 Pa\sdot 1.8\sdot 10^{-3} m^3=270J;$

$U=Q-A;$

$U=1000J-270J=730J;$

Answer: $U=730J.$