[化學] 熱力學

作者: essential35 (essential)   2016-09-15 01:31:40
想問幾道題。
1、在與外界隔離系統中,假設一塊溫度為100。C重量50g的銀(比熱=0.2350J/g。C),
和溫度為0。C重量50g的鐵塊(比熱=0.4494J/g。C)放置接觸在一起,最後兩塊金屬的
溫度為何?
(a)將高於50。c (b)將低於50。C (c)恰好為50。c (d)無法預測
我寫的是d,不知道對不對
2、What is the Cp(the molar heat capacity) of a gas which Cv=48J/mol.K at 298K?
這題不知道從何下手。會用到杜龍-博蒂定律嗎?想請教一下這個定律是怎麼一回事。
3、A gas absorbs 100J of heat and is simultaneously compressed by a constant
external pressure of 1.5 atm from 8.0 to 2.0L in volume. What is <|U in Joules
for the gas.
(a)-812 (b)+812 (c)-912 (d)+912 (e)1012
4、30。C下,某理想氣體5.0mol 具有20L 體積,當進行可逆壓縮時,放出熱量為
5.82*10(11次方)erg,試問其最終體積為:
(a)0.0394 (b)0.0287 (c)0.1970 (d)0.0788 L
我寫A,不知道對不對。
希望各位可以幫我,感激不盡。
作者: guitarspirit (e^ipi=-1)   2015-04-05 09:07:00
1.系統是鐵和銀且由題意可知From 1st law ΔU=Q+W=ΔU(Fe)+ΔU(Ag)=0m(Fe)*C(Fe)*(Tf-T(Fe))+m(Ag)*C(Ag)*(Tf-T(Ag))=02. For ideal gas Cp=Cv+R3.For expansion of an ideal gas at constant PFrom 1st law ΔU=Q-P(Vf-Vi)4. For compression of an ideal gas at constant TFrom 1st law Q=nRTln(Vf/Vi)

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