作者k0185123 (Ethan)
看板Chemistry
标题[学科] 物化绝热过程
时间Mon Oct 19 16:18:35 2009
教授说这题要以绝热过程来计算，但我还是算不出来，
我是对课本後面的答案..虽然有可能错（教授说的），但是应该不会那麽刚好吧- -
Initially 5 mom of nitrogen are at a temperature of 25℃ and a pressure
of 10 bar. The gas may be assumed to be ideal; Cv,m = 20.8 JK^(-1)mol^(-1)
and is independent of temperature. Suppose that the pressure is suddenly
dropped to 1bar; calculate the final temperature, ΔU, and ΔH.
拜托了-.-
我算末温是154.47K，答案却是221K...也因此後面两者都错了..
算法是：
用 PV=nRT，算出原本体积为12.385(L)
再用 P1V1^γ = P2V2^γ，算出V2为64.17(L)
接着再以
P1V1:P2V2 = T1:T2 ， 求T2.....就变成154.47..了ˊˋ
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※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 140.112.250.70
1F：推 edisonjang:若可逆 (T2/T1)=(P2/P1)^(γ-1/γ) T2=154047 +1 10/19 17:48
2F：→ edisonjang: =154.47 10/19 17:50
3F：→ k0185123:原题有把suddenly用斜体字.. 10/19 18:46
4F：推 edisonjang:那蛮怪的 决热不可逆 W=-∫P外dV=0 10/19 18:52
5F：→ edisonjang:U = q+W = 0+0 = 0 10/19 18:53
6F：→ edisonjang:说错 10/19 18:55
7F：→ edisonjang:绝热不可逆 不可用PV^γ=K 10/19 18:56
8F：→ edisonjang:q=0 U=W=-P外dV =>Cv(V2-V1)=P外(nRT2/P2-nRT1/P1)解 10/19 18:58
9F：→ edisonjang: -P外 10/19 18:59
10F：推 SHENG3106:请问最後答案是多少 10/19 22:49
11F：→ SHENG3106:Cv(T2-T1)=-R(T2-(P2/P1)T1) 10/19 22:50
12F：推 Corsairs:我算248K耶 =_= 10/20 01:36
13F：→ k0185123:221k = answer -.-....... 10/20 13:19
14F：推 SHENG3106:我想问的是H U答案 10/20 14:54
15F：推 edisonjang:U = CvΔT H = CpΔT = Cv+nRΔT 10/20 17:42