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发表于 24-8-2006 03:00 PM
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原帖由 jayck 于 24-8-2006 11:05 AM 发表
问题25In the line emission spectrum of hydrogen , how many lines can be accounted for by all the possible electron transition between the five levels of lowest energy within the atom.
A. 4 B. ...
D 10 gua |
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发表于 24-8-2006 03:04 PM
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原帖由 jayck 于 24-8-2006 10:48 AM 发表
答案是B
When electron falls from a higher level to a lower level ,excess energy is given out as radiation with certain frequency.
And this frequency is determine by the two level involve in t ...
这题我有做过。我也认为答案是C。结果答案是B。我觉得两个答案都好像是对的。有谁可以清清楚楚的告诉我为何答案是B而不是C?哪一个较tepat? |
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发表于 24-8-2006 07:04 PM
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好吧!是时后进入 23 ... [/quote]
Question 23 的答案是不是这样?
propan-2-ol 先undergoes dehydration变成propene.
then propene reacts with HCN(aq)[nucleophilic addition] to form
CH3CH(CN)CH3.
then CH3CH(CN)CH3.undergoes hydrolysis(dilute HCl+reflux)to form 2-methylpropanoic acid.对吗? |
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楼主 |
发表于 24-8-2006 07:32 PM
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alkene 应该不能做nuceophilic addition 吧?(electrophilic addition 才可以) |
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发表于 24-8-2006 07:46 PM
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原帖由 dunwan2tellu 于 24-8-2006 07:32 PM 发表
alkene 应该不能做nuceophilic addition 吧?(electrophilic addition 才可以)
对ho,paiseh electrophilic addition才对。谢谢提醒。。。 |
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发表于 24-8-2006 08:47 PM
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回复 #62 hvaly 的帖子
energy 的level 会随时改变的,absorb 和release的energy当然也是不定的及不连续的. |
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发表于 24-8-2006 09:42 PM
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原帖由 jayck 于 24-8-2006 08:47 PM 发表
energy 的level 会随时改变的,absorb 和release的energy当然也是不定的及不连续的.
paiseh...我还是不是很懂。。。。。
B 有解释到为何有 line spectrum吗?
就算是between 2 energy levels有energy but 如果没有emit出来怎样会有line spectrum呢?C的答案为何不被accept? |
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发表于 25-8-2006 11:07 AM
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原帖由 hvaly 于 24-8-2006 03:00 PM 发表
D 10 gua
答案是对了
但我不明白为何是10哦..
有谁可解释
24题..我已无法给你更进一步的了解了.不好意思 |
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楼主 |
发表于 25-8-2006 11:15 AM
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原帖由 jayck 于 25-8-2006 11:07 AM 发表
答案是对了
但我不明白为何是10哦..
有谁可解释
24题..我已无法给你更进一步的了解了.不好意思
因为你有 5 个 energy level , i.e n=1,2,3,4,5
所以你可以是 n=5-->1 , n=4-->1,n=3-->1,n=2-->1 ,n=5-->2,n=4-->2,n=3-->2,n=5-->3,n=4-->3,n=5-->4
以上是transition of electron from higher energy level to lower energy level 的方法.共有十种
23题提示:先把 propan-2-ol convert to haloalkane 然后就能用 SN1/SN2 (nuceophilic substitution)加给他一个 C .
[ 本帖最后由 dunwan2tellu 于 25-8-2006 11:18 AM 编辑 ] |
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发表于 25-8-2006 02:17 PM
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原帖由 dunwan2tellu 于 25-8-2006 11:15 AM 发表
因为你有 5 个 energy level , i.e n=1,2,3,4,5
所以你可以是 n=5-->1 , n=4-->1,n=3-->1,n=2-->1 ,n=5-->2,n=4-->2,n=3-->2,n=5-->3,n=4-->3,n=5-->4
以上是transition ...
好好..谢了.
下一题是什么..
谁提供 |
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楼主 |
发表于 25-8-2006 04:06 PM
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问题26
What is the shape of
(i)H2O
(ii) H3O(+) |
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发表于 26-8-2006 12:31 AM
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发表于 26-8-2006 09:19 AM
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原帖由 dunwan2tellu 于 25-8-2006 04:06 PM 发表
问题26
What is the shape of
(i)H2O
(ii) H3O(+)
(i)H2O = V-shape
(ii)H3O+ = piramid
问题26
which one of the following has the same number of electron as an alpha particle?
A. H
B. H+
C. H2
D. He
E. Li+ |
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发表于 26-8-2006 11:32 AM
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问题26
which one of the following has the same number of electron as an alpha particle?
A. H
B. H+
C. H2
D. He
E. Li+ [/quote]
B:H+ |
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发表于 26-8-2006 01:27 PM
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原帖由 jayck 于 26-8-2006 09:19 AM 发表
(i)H2O = V-shape
(ii)H3O+ = piramid
问题26
which one of the following has the same number of electron as an alpha particle?
A. H
B. H+
C. H2
D. He
E. Li+
question 25
i) V shape
ii) trigonal pyramid
Question 26
答案不是D Helium 吗? |
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发表于 26-8-2006 01:31 PM
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Question 27:
Which of the following has the least effect on the retention time of a component?
A relative molecular mass
B density of molecule
C polarity of molecule
D shape of molecule |
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发表于 26-8-2006 04:39 PM
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原帖由 hvaly 于 26-8-2006 01:27 PM 发表
question 25
i) V shape
ii) trigonal pyramid
Question 26
答案不是D Helium 吗?
错了.
答案是B. H+
alpha particle is a helium necleus,i.e.He2+ and 是没有electron 的. |
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发表于 26-8-2006 04:41 PM
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发表于 26-8-2006 04:54 PM
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原帖由 jayck 于 26-8-2006 04:41 PM 发表
会是D吗?
...
答案是B。boiling point和volatility会影响retention time。
如果molecular mass高,higher boiling point, less volatile。
如果molecule是polar的, higher boiling point, less volatile。
如果molecule有branch,lower boiling point,more volatile....
so答案是B。 |
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发表于 26-8-2006 07:14 PM
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Q28:
The bonding in compound XY tends to be more electrovalent than covalent if
A size of anion Y is small
B size of cation X is small
C charge of cation X is large
D ionisation potentials of X and Y are nearly the same
E X and Y have a small difference in their electronegativity |
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