作者water0bearer (霖)
看板TransBioChem
標題Re: [化學] 中興化學問題
時間Sat Jul 2 21:59:22 2011
※ 引述《sparkle0829 (sparkle)》之銘言:
: ......
: 98.3. Consider the following chemical reaction: 2A + 2B → C Overall reaction
: Reaction mechanism: Step1. A+B→D
: Step2. D+B→M
: Step3. A+M→C
: Which one of the following rate laws is consistent with this mechanism?
: (A) Rate = k[A]^2 [B] (B) Rate = k[D][B] (C) Rate = k[A][B]
: (D) Rate = k[A] [B]^2 (E) The information is not sufficient
: →請問這樣列是錯哪?
: Step3: K2 = [M]/[D][B] ; K1 = [D]/[A][B] ; [M]=K2[D][B]=K2K1[A][B]^2
: Rate[C] = K3[A][M] = K1K2K3 [A]^2 [B]^2
我認為是E,不知道哪一部是速率決定步驟~
: 98.6. Gasoline was injected into the cylinder and was ignited. A piston moved
: outwardly of the cylinder while exposition took place inside the motor
: engine. Which of the following statements is not accurate ?
: (A) It is an example of converting chemical energy to mechanical work.
: (B) The motor engine had done work to the surrounding.
: (C) The temperature dropped down after the piston moved out.
: (D) All the energy released from the burning of gasoline was converted
: to the work done to the surrounding.
: (E) It was an irreversible process.
: →是否選E,不可逆表自發,但其被ignite才氣體膨脹?
E是對的,答案我認為應該是D。
現實生活中幾乎所有的反應在熱力學夏都是不可逆的(不能回到原本的狀態)。
引擎燃燒爆炸有一大部分的能量變成熱能散失到surrounding,
並沒有全部用來做功!
: 98.10. Which of the following statements is wrong about thermodynamics ?
: (A) The entropy of any substance(element or compound)in its equilibrium
: state approaches zero at the absolute zero of temperature.
: (B) The absolute value of the Gibbs free energy of a substance can't
: be determined.
: (C) The Gibbs free energy is zero during phase transitions of a pure
: substance.
: (D) The absolute value of the entropy of a substance can't be
: determined.
: (E) A spontaneous process is always an irreversible process.
我猜是C,相變化自由能會變吧!
: 95.29. What is W in Boltzmann's formula, S=k x InW
: (A) a fraction indicating the probability of obtaining a result
: (B) a random number
: (C) the number of ways of obtaining the state
: (D) the work times Avogadro's number
: →請問這定律是?
應該是A,
普化課本有這個方程式,我記得~
你可以查看看書本後面的字母索引!
: 94.18. If the temperature of the reaction is decreased, what is the effect on
: the equilibrium constant and ΔG ?
: N2(g) + 3H2(g) → 2NH3(g),ΔH+ = -92.4 kJ/mol
: (A) K increases, ΔG increases
: (B) K decreases, ΔG decreases
: (C) K increases, ΔG decreases
: (D) K decreases, ΔG increases
: (E) Temperature does not affect equilibrium or ΔG
: →請問G是?1. K↑,G= -RTlnK (兩個變因 T↓K↑)
: 2. K↑,G= H-TS, T減少到負值,此時G↑ 故選A?
K會上升你知道,
G的部分我認為這個反應在低溫會趨向自發,
所以溫度越低ΔG應該愈來愈小~
: 94.非選擇題1. Please describe how to set up the physical structure of atom using the
: experimental findings.
: 題目有點多T_T 今天被教授劣退 有請各位大大幫忙了!感恩!!
抱歉~目前手邊沒有計算紙與筆,
也沒有普化課本,
先回答你這樣,
沒回答的另請高手幫忙~
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1F:推 veryblack:98.3=你的想法是對的 不知道哪一步是決定步驟(slow) 07/02 23:19
2F:→ veryblack:98.10=純物質相變化時自由能變化為零喔 是亂度會變 07/02 23:20
3F:推 veryblack:所以是D 亂度可以直接求出值 07/02 23:22
4F:→ veryblack:這年我有考過= = 不過熱化學一年沒碰了大概只記得這些 07/02 23:22
5F:→ sparkle0829:水大和v大先謝謝你們 94.18怎麼判斷低溫趨向自發? 07/02 23:29
6F:推 sparkle0829:另外亂度 不是要計算系統與環境?不是因為不好測所以才 07/02 23:34
7F:→ sparkle0829:改用ΔG只需檢測系統資料 因為環境不知道怎麼測? 07/02 23:36
8F:推 veryblack:亂度質有公式可以帶 07/02 23:45
9F:→ veryblack:G(自由能的話) 則只能求出變化量 無法得知其值是多少 07/02 23:45
10F:→ veryblack:94.18=利用deltaG = deltaH - T x deltaS 07/02 23:47
11F:→ veryblack:利用deltaG>0可自發<0非自發來判斷 07/02 23:47
12F:→ veryblack:而T是絕對溫度 故其值必大於零 07/02 23:48
13F:→ veryblack:所以就可以得知當deltaH>0時 若deltaS也大於零 07/02 23:49
14F:推 sparkle0829:了解! 07/02 23:49
15F:→ veryblack:更正 若deltaS小於零時 算出來deltaG必大於零 自發 07/02 23:50
16F:→ veryblack:反之就必小於零 非自發 07/02 23:50
17F:推 sparkle0829:這題沒給s 是否用S=H/T 07/02 23:53
18F:推 veryblack:deltaS可以自行判斷 例如液相便氣相會變大之類的 07/03 00:10
19F:→ veryblack:反應過程中莫耳數變少亂度也是下降 07/03 00:11
20F:→ veryblack:因此可以得知deltaS<0 07/03 00:11
21F:推 sparkle0829:所以ΔS<0 ΔT<0 此G應該為下降了 07/03 00:17
22F:推 veryblack:可是這題的溫度有改變所以不是用這條公式= = 07/03 00:18
23F:→ veryblack:不好意思我剛沒注意到 07/03 00:18
24F:推 sparkle0829:ΔG=Δ(H-TS)=ΔH-T*ΔS-S*ΔT 我好像越來越模糊了XD 07/03 00:30
25F:推 veryblack:還是請專家解釋好了XD 07/03 03:29
26F:→ veryblack:這題我那時候很直接的想K變大deltaG必變更小(負更大) 07/03 03:30
27F:→ veryblack:剛翻了一下普化還是想不出解釋方式 07/03 03:30