1)

An office room contains about 2000 moles of air. The change in the internal energy of this much air when it is cooled from 340C to 240C at a constant pressure of 1.0 atm is 

[ Use γair=1.4 and universal gas constant =8.314 J/mol-K]


A) 1.9×105J

B) +1.9×105J

C) 4.2×105J

D) +0.7×105J

Answer:

Option C

Explanation:

 Given, 

 Number  of moles of air in room (n)=2000= 2×103

 Temperature difference (dT)=24-34=100C

 We know that,

 dQ=nCvdT=2×103×R0.4[10]

 = 2×103×8.314×100.4

  =2×8.314×1054=16.6284×105

   =4.2×105 J