作者nauticat (我是野男人)
看板TransBioChem
标题[化学] 问题请教
时间Sun Jun 12 10:20:35 2011
几题化学请教 谢谢
1. which of the following electromagnetic radiations corresponds to the
dipole transition of pure molecular rotation?
a) UV light b) IR radiation c) microwaves d) radio wave
小弟查不到有关分子转动的偶极跃迁和四种波的关系, 讨教一下
2. The ionization energy of H atom is 13.6 eV. What is the second
ionization energy of He atom?
a) 6.8 eV b) 13.6 eV c) 27.2 eV d) 54.4 eV
小弟写 b , 因为He有两个电子,第二颗跟H的一样,对嘛???
另外H是不是没有第二游离能???
3. Which of the following combination of quantum numbers n and l are
forbidden? a) 5d b) 6f c) 8s d) 4f
小弟觉得四个都可以, 是题目有问题嘛?
4. Calculate the pH of a solution made by mixing 50.0 ml of 0.400 M NaA
(Ka for HA= 1.0 * 10*-8) with 50.0 ml of 0.100 M HCl .
a) 3.65 b) 7.52 c) 8.48 d) 11.6
小弟本来是这样算: HCl是强酸 直接算浓度 ( 0.1M * 50ml ) / (50ml+50ml)
会得到 [ H+] = 0.05 M = 5 * 10*-2 pH = 2-log5 =1.31 (? 没这选项)
後来查书 两种氢离子的浓度要相加:
HCl -----> H+ + Cl- 所以 [H+] = 0.05 M 盐酸的氢离子
NaA + H2O ----> A- + H3O+
0.2 0.05 (盐酸来的)
-X +X +X
-----------------------------------------
0.2-X +X 0.05+X
所以 X*(0.05+X) / 0.2-X = Ka = 1.0 * 10*-8
算出来 X = 4 * 10*-8 而 [H3O+] = 0.05 + 4 * 10*-8 (很小吧!)
pH = 1.31 跟上一个算法一样!!?? 请问我哪边算错了呢?
5. An ideal gas expands to the vacuum isothermally and irreversibly
delta U is
a) less than zero b) equal to zero c) greater than zerp d) more
information is needed
小弟选 d , 因为看不出来 哈哈哈
麻烦大家了 谢谢~
--
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1F：→ RLCorn:2.氦气第二游离能 He(g)+→e- + He(g)2+ 已成类氢原子 06/12 14:58
2F：→ RLCorn:4.考虑同离子效应 "虽说几乎"由强酸提供[H+] 但盐类水解 06/12 15:01
3F：→ RLCorn:亦须考虑进去 06/12 15:02
4F：→ angel30hyt:3.没有8S周期表只有到7S 06/12 21:40
5F：→ angel30hyt:1.应该是C 06/12 21:47
6F：→ luky60311:第4的概念完全错了 06/12 21:47
7F：→ luky60311:弱酸的共轭酸根必须视为"硷" 06/12 21:48
8F：→ angel30hyt:Rotational spectroscopy or microwave spectroscopy 06/12 21:48
9F：→ angel30hyt:studies the absorption and emission of 06/12 21:48
10F：→ angel30hyt: electromagnetic radiation (typically in the 06/12 21:49
11F：→ luky60311:也就是(1)先进行酸硷作用 使[HA]反应後变成0.05M 06/12 21:49
12F：→ angel30hyt:microwave region of the electromagnetic spectrum) 06/12 21:49
13F：→ luky60311:[A-]变成0.15M 06/12 21:50
14F：→ luky60311:(2)再带入Ka就可算出[H+] 06/12 21:50
15F：→ angel30hyt:by molecules associated with a corresponding change 06/12 21:50
16F：→ angel30hyt: in the rotational quantum number of the molecule. 06/12 21:51
17F：→ luky60311:完全根A-水解无关 06/12 21:52
18F：→ nauticat:谢谢了~ 自己念有时候真的转不太过来 XD 06/12 22:01
19F：→ c510518:5.ideal gas的u只和温度变化有关 应该是0吧~ 06/13 19:44
20F：→ nauticat:请问luky大 这两个不是都是酸吗?这样可以酸硷反应嘛?谢谢 06/13 21:25
21F：推 luky60311:[A-]为硷 如果有chemical principles 可参考盐类水解 06/13 21:46
22F：→ luky60311:盐类之所以会水解(和H2O)反应是因为水中没有大量H+建立 06/13 21:48
23F：→ luky60311:平衡系 但本题有H+(盐酸提供)建立平衡系 06/13 21:49
24F：→ luky60311:参考教科书应该就能懂A-为何是为硷 06/13 21:50
25F：→ nauticat:好~感谢! 06/13 22:37
26F：推 knight791211:你也要考嘉义对吧 一起加油吧 06/27 21:31