物理化学电子教案第二章(下) 热力学第一定律及其应用 环境 surroundings 无物质交换 封闭本系 closed system △U=Q+W 能量交换 4上一内容下一内容令回主目录 返回 2021/223
上一内容 下一内容 回主目录 返回 2021/2/23 物理化学电子教案—第二章（下） = + U Q W
Adiabatic process In Fig Pv T In reversible process the work A() done (below the line ab) is B/p: V,) big than the work done(below the line ac)in adiabatic Clp: v,) reversible process Slope in ab: 图1.6绝热可逆过程(AC)与 等温可逆过程(AB)功的图解(示意图) Slope in ac Os==yp yy>I 4上一内容下一内容◇回主目录 返回 2021/223
上一内容 下一内容 回主目录 返回 2021/2/23 Adiabatic process In Fig.PV: Slope in AB： ( )T p p V V = − Slope in AC： ( )S p p V V = − In reversible process the work done （below the line AB）is big than the work done (below the line AC) in adiabatic reversible process. 1 T
Fig. adiabatic and isothermal rev. process In an isothermal p expansion heat continuously flows B/: Vy) Into the system, and so the e pressure a C(p: V, does not fall as much as in a the ermally isolated adiabatic F 图1.6绝热可逆过程(AC)与 expansion 等温可逆过程(AB)功的图解(示意图) 4上一内容下一内容令回主目录 返回 2021/223
上一内容 下一内容 回主目录 返回 2021/2/23 Fig. adiabatic and isothermal rev. process In an isothermal expansion heat continuously flows into the system, and so the pressure does not fall as much as in a thermally isolated ,adiabatic expansion
Work in adiabatic process (1)work in pg. a. r. process K y (P=K) K 1 ecause P,li=p,l=K therefore W=p22-p, V nR(T-T) 4上一内容下一内容令回主目录 返回 2021/223
上一内容 下一内容 回主目录 返回 2021/2/23 Work in adiabatic process （1）work in pg. a. r. process. 2 1 = d V V K V V − 1 1 2 1 = 1 1 ( ) (1 ) K V V − − − − − therefore 2 2 1 1 = 1 p V pV W − − p V p V K 1 1 2 2 because = = 2 1 d V V W p V = − ( ) pV K = 2 1 ( ) 1 nR T T − = −
a better calculation method (2)another way to calculate W=△U=2CdT C(2-7)(设G与7无关) This equation is true for all adiabatic expansions or contractions involving a perfect gas or not, reversible or not 4上-内容下一内容令回主目录 返回 2021/223
上一内容 下一内容 回主目录 返回 2021/2/23 A better calculation method （2）another way to calculate W U = This equation is true for all adiabatic expansions or contractions involving a perfect gas or not, reversible or not. 2 1 = ( ( ) C T T V C T V − 设 与 无关） 2 1 d T V T = C T