STPM化学专区

vick5821

Then can you show the working? I think I get abit abit nia

四月一日的小皮

4n/6.02x10^23 = 501.6/209
n=?
then,
n/6.02x10^23 =65/Mr
Mr=?

vick5821

Ok..understand..thx..U upper six?

四月一日的小皮

waiting for result

vick5821

what is ur email address?? whcih one is you?

四月一日的小皮

-feni-lelouch

vick5821

I where got add u b4 leh

silent91

请问～

问题：compare the boiling point of butane, & 2, methylpropane.
答案会有什么关于polarised的东东没有？

四月一日的小皮

请问～

问题：compare the boiling point of butane, & 2, methylpropane.
答案会有什么关于polarised的 ...
silent91 发表于 26-2-2010 10:07 PM

it is not related to polarise.
it is more related to the length of carbon atom(branching).

silent91

it is not related to polarise.
it is more related to the length of carbon atom(branching).
四月一日的小皮 发表于 26-2-2010 10:23 PM

哦～谢谢～

因为补习老师给错的指引，然后找书找不到～
所以就～～～～～

海涵

请教一下这题怎么做。。
The melting of ice at body tempterature is an endothermic process:
    H2O(s) -->H2O(l)   ;  ∆H = +6.0kJ/mole
Thus eating ice counteracts the exothermic processes of metabolising food. How much ice (in grams) would you have to eat to counteract the energy gained by eating 1.00 oz of peanuts(13kJ/g) ?          (1 oz = 28.3)

四月一日的小皮

１oz有２８.3g
so，１oz的peanut就produce =
（２８.３ x １３k ）J = ３６７.９kJ
mole of water to counteract= (367.9k/ 6k) = 61.31mole
1 mole of water have 18g of water.
thus, (61.31 x 18) = 1103.58g

好像有点错...

海涵

答案有
A) 61g  
B)78g   
C)110g  
D)370g   
E)1100g

海涵

答案有
A) 61g  
B)78g   
C)110g  
D)370g   
E)1100g

數學神童

Why a mixture of ethanoic acid and sodium ethanoate can act as a buffer solution
i)addition of acid
ii)addition of alkali

外星護法

1.) A sample of 1.2-dimethylbenzene is oxidised to its corresponding dicarboxylic acid. What is the mass if the product if 1.00g of 1,2-dimethylbenzene is used ???

2.) Cis and trans isomers have different chemical and physical properties ... 这句话对还是错 ？？

3.） benzene, chlorobenzene, methylbenzene。。 怎样看他们的reactivity ?? 哪一个比较强 ？？？

4.）请问要怎样看一个molecule有没有coordinate bond ?? like NO3(1-) and  SO4 (2-) ?

5.) intermolecular forces for dry ice is ???

6.) 两种不同的ideal gas 可不可以 share the same p-v curve  if temperature for both gases are the same ??

谢谢~~

whyyie

回复 559# 外星護法


    2) 错. cis-trans isomers have same chemical properties but different physical properties.

其他的不是很确定, 不敢答.

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 ??