5 moles of helium expand isothermally and reversibly from a pressure `40xx10^(-5)Nm^(-2)` to `4xx10^(-5)Nm^(-2)` at 300 K. Calculate the work done, change in internal energy and heat absorbed during the expansion . `(R=8.314Jk^(-1)"mol"^(-1))`

Explanation

Given,
Number of moles `=5`
Initial pressure `P_(1)=40xx10^(-5) Nm^(-2)`
Final pressure `P_(2)=4xx10^(-5)Nm^(-2)`
Temperature `=300 K`
Work done `=?`
`W=-2.303 nRT log_(10).(P_(1))/(P_(2))`
`=-2.303xx8.314xx5xx300 log_(10).(40xx10^(-5))/(4xx10^(-5))`
`=-2.303xx12471xxlog_(10)10`
`=-2.303xx12471xx1`
`=-28720.713 J`
`W=-28.720kJ`
`rArr` For isothermal process change in internal energy
`(DeltaU=0)=`zero
`rArr DeltaU=q+W`
`0=q+W`
or `q=-W`
`q=28.720 kJ`
`:.28.720` kJ heat absorb during expansion.