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 CExplanation: 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