. A gas is allowed to expand in a well insulated container against a constant external pressure of


2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy U of the gas in joules will be

(a) - 500 J

(b) - 505 J

(c) + 505 J

(d) 1136.25 J

Best Answer

Correct Option is : (b)

HINT 1- WELL  INSULATED  CONTAINER

which means the process is adiabatic

so q=0

 w = –PextdV 

w= -2.5(4.5-2.5) = -5Latm =5*101.325 J = 506.6 J

According to the first law of thermodynamics

U=q  + w 

U= 505 J (approx)

 

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