12. A cylinder contains 1.2 moles of ideal gas, initially at a temperature of 116℃. The cylinder is provided with a frictionless piston, which maintains a constant pressure of 6.4 x 10⁵ Pa on the gas. The gas is cooled until its temperature has decreased to 27℃. For the gas Cy= 11.65 J/molㆍK, and the ideal gas constant R = 8.314 J/mol.K.
(A) The work done by the gas during this process is 890 J.
(B) The work done on the gas during this process is 890 J.
(C) The change in the internal (thermal) energy of the gas during this process is +1200 J.
(D) The heat transferred from the gas during this process is -1200 J.
(E) The heat transferred to the gas during this process is +2100 J.

詳解 (共 2 筆)

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B1 · 2025/10/30

#6995567

1. 題目解析 這道題目涉及理想氣體的熱...

(共 1549 字，隱藏中）

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B2 · 2026/06/16

#7409395

所以解答這題有哪些條件來解

第一個溫度差為89k

溫度差為負的

後來的溫度減掉原來的溫度

所以為負的(冷卻)

所以定壓下，氣體作功

所以氣體對外作功(gas done by gas)

結果是負的，代表氣體不是對外作功，而是被外界壓縮

所以

ㅤㅤ

然後內能作功會等於n*Cv*deltaT

算出來為負的

所以內能是減少而不是增加

然後熱量變化

用熱力學第一定律

內能變化，會等於吸熱所作的功-對外作功

所以移項一下

ㅤㅤ

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