作者k0185123 (Ethan)
看板Chemistry
標題[學科] 物化絕熱過程
時間Mon Oct 19 16:18:35 2009
教授說這題要以絕熱過程來計算，但我還是算不出來，
我是對課本後面的答案..雖然有可能錯（教授說的），但是應該不會那麼剛好吧- -
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.
拜託了-.-
我算末溫是154.47K，答案卻是221K...也因此後面兩者都錯了..
算法是：
用 PV=nRT，算出原本體積為12.385(L)
再用 P1V1^γ = P2V2^γ，算出V2為64.17(L)
接著再以
P1V1:P2V2 = T1:T2 ， 求T2.....就變成154.47..了ˊˋ
--
※ 發信站: 批踢踢實業坊(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:原題有把suddenly用斜體字.. 10/19 18:46
4F：推 edisonjang:那蠻怪的 決熱不可逆 W=-∫P外dV=0 10/19 18:52
5F：→ edisonjang:U = q+W = 0+0 = 0 10/19 18:53
6F：→ edisonjang:說錯 10/19 18:55
7F：→ edisonjang:絕熱不可逆 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:請問最後答案是多少 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:我想問的是H U答案 10/20 14:54
15F：推 edisonjang:U = CvΔT H = CpΔT = Cv+nRΔT 10/20 17:42