STPM化学专区

四月一日的小皮

答案有
A) 61g  
B)78g   
C)110g  
D)370g   
E)1100g
海涵 发表于 14-3-2010 03:03 PM

应该是E。

四月一日的小皮

1.) A sample of 1.2-dimethylbenzene is oxidised to its corresponding dicarboxylic acid. What is the  ...
外星護法 发表于 23-3-2010 06:47 PM

1. 1.2-dimethylbenzene  + 6[O]  -> 1,2-dimethylbenzene + 2 H2O

r.m.m of 1.2-dimethylbenzene = 106 g/mol
r.m.m of 1,2-dimethylbenzene = 166 g/mol
mole of 1g of 1.2-dimethylbenzene = 1 /106 mol
1mole of 1.2-dimethylbenzene produce 1 mole of 1,2-dimethylbenzene(according to eqn)
thus,mass of 1,2-dimethylbenzene = 1/106 x 166 = 1.57g (3.s.f)

2.aswhyyie  say above.

3.depend the side group...it divide into two group: electron-donating group and electron-accepting group.
in benzene,electron-donating group will make the benzene ring more reactive; while electron-accepting group will make benzene ring less reactive. more detail u should refer to chapter regarding benzene.

4.Co-ordinate bond - dative bond, can be formed by sharing electron within 2 atom in which both the sharing electron is contributed by 1 of the atom.however, in case of NO3(1-) and  SO4 (2-) ,u should refer to ' delocalisation' or 'resonance' .

5. weak wan der waal force of attraction.

6.nope, definitely because each ideal gas have its own p-v curve when temperature is the same.it is depend on its intermolecular attraction of force.let me ask you, if same temparature of water and iodine does they have same p-v curve?u should know that hydrogen bond is different with weak van der waal force of attraction.

外星護法

1. 1.2-dimethylbenzene  + 6[O]  -> 1,2-dimethylbenzene + 2 H2O

r.m.m of 1.2-dimethylbenzene = ...
四月一日的小皮 发表于 23-3-2010 11:53 PM

   
thanks for answering~

no 3... isn't most of the electron-donating group have a double bond ??

no 5... may i know what is the chemical composition for dry ice ?? isn't CO2 ??

for no6, i thought one of the assumption for ideal gas  is intermolecular forces btw molecule can be negligible ??

四月一日的小皮

thanks for answering~

no 3... isn't most of the electron-donating group have a double ...
外星護法 发表于 24-3-2010 10:49 PM

nope...see alkyl group. -CH3 btw.some of the group r NH2,OH2...
yes...dry ice is CO2.
lol...i tought i say real gas. i think for real gas to achieve ideal properties,they need high temperature and low pressure,but varies on which extent.

silent91

请问ethene + aqueous Br2 in dark condition会有什么product?
除了1,2-dibromoethane.

语曦

回复 565# silent91


   2-bromoethanol

silent91

回复  silent91


   2-bromoethanol
语曦 发表于 28-3-2010 12:32 PM

1) add ethene with Br2 in CCl4 will become 1,2-dibromoethane
2) add ethene with bromine water will become 1,2-dibromoethane & 1-bromoethanol

以上的statement对吗？

语曦

回复 567# silent91
correct,major product is 2-bromoethanol,minor product is 1,2-dibromoethane.

數學神童

Barium ions are poisonous. In 'Barium Meal' test for patients with stomach ulcer, the patient is required to drink a suspension of BaSO4 in water before the X-ray is taken.Explain why BaCO3 is not used in 'Barium Meal' test

白羊座aries

The rate equation for the decomposition of hydrogen iodide is , rate = k[HI]^2
The rate constant at temperature at T1 and T2 are 1/2k and 2k respectively.
The decomposition rate at these temperature are r and 16r respectively .If the pressure of HI at temperature T1 is p,calculate the pressure of HI at temperature T2

tiewkj

请问下methylbenzene undergo oxidation的observation,除了purple colour of KMnO4 is decolourised之外，是不是还要写white percipitate of benzoic acid is formed?因为我最近换老师，以前那个老师讲不用，现在这个讲要，补习老师没讲过～谁能帮帮我？谢谢～

四月一日的小皮

好像这里最近没人来解答了...

５６９＃
我们的胃酸液是hydrochloric acid。
由于Ba ion对人体有是有害的，所选用的Barium chemical就rather不会被人体吸收。BaSO４只所以能运用在Barium Meal是它是insoluble，对人体的伤害减少。BaCO３，跟HCl react会form成BaCl２，是一种water－soluble的salt。

５７０＃
rate = K[HI]^2
at T１， K= １／２k
rate= r ， pressure=p ；
at T２， K= ２k
rate= １６r，pressure=？；
我们知道，ROR会受到pressure影响。
问题是，在这里，要怎样show pressure影响ROR？
［HI］可以是in concentration。或是in pressure。
HI的decomposition是从以下的equation形成。
2 HI(g) <--> H2(g) + I2(g)
所以， at T１， r = ０.５k［p］＾２
at T２， １６r=２k[HI]^2
用division方式，找到１６［p］＾２= ４[HI]^2
最后就找到[HI]=２p
{不懂对不对，由于题目的clue给予太不明确。}

５７１＃
写下去，因为分数不会被deduced掉。
对就有分，错的话若有其他答案就不回被扣分。

tiewkj

回复 572# 四月一日的小皮

可是我朋友说benzoic acid有OH,所以会dissolve 在水里面，那还会有percipitate 吗？

四月一日的小皮

回复 573# tiewkj

benzoic acid是aromatic carboxylic acid。
aromatic carboxylic acid比较less soluble in water，由于benzene ring的影响。

tiewkj

回复 574# 四月一日的小皮

好的～谢谢～那就是说写下去有white percipitate of benzoic acid form比较好对吗？分数才不会被扣掉～谢谢你啊～

白羊座aries

所以， at T１， r = ０.５k［p］＾２
at T２， １６r=２k[HI]^2
用division方式，找到１６［p］＾２= ４[HI]^2
最后就找到[HI]=２p

不明白这里，可以详细地解释吗？

四月一日的小皮

回复 576# 白羊座aries


运用回Rate of reaction，R = K［HI］＾２
在T１的时候，K=０.５k，［HI］=p，R = r；
把所有的data放进rate equation里：

r=０.５k(p^2) ............(1)

在T２的时候，K=２k，［HI］=x，R=１６r；
然后得到的equation是：

１６r=２k(x^2)............(2)

过后就用mathematics的方法，用（２）除（１）：

１６r／r  = ２k（x）＾２ ／ ０.５k（p）＾２
    １６  = ４（x）＾２ ／ （p）＾２
      ４ = （x／p）＾２
      ２ =   x／p
      x  =  ２p

白羊座aries

回复  白羊座aries


运用回Rate of reaction，R = K［HI］＾２
在T１的时候，K=０.５k，［HI］=p，R  ...
四月一日的小皮 发表于 5-4-2010 11:51 PM

谢谢，终于明白了

yhuai

我想请问下哪里可以找到organic chemistry的notes?

meiling

回复 579# yhuai


上网看了看。。
看到这个。。
http://pdfdatabase.com/organic-chemistry-stpm.html
和这个  http://bombbook.filegranted.com/ ... mistry+stpm&amp;afid=9
不过我没有开来看，所以不知道能不能用的