STPM化学专区

SteveLovers

I think that if u just spot to pass the chemistry...
then u must study and understand all the physical chemistry...
becoz a lot question come out from there.

silent91

I think that if u just spot to pass the chemistry...
then u must study and understand all the physi ...
SteveLovers 发表于 2-8-2010 10:09 PM

  读一本就及格，那另外两本拿来摆？

vick5821

What is a dipole moment??

Bayleaf

What is a dipole moment??
vick5821 发表于 6-8-2010 11:40 PM

The product of the magnitude of the partial charges (δ+ and δ-) of a molecule times the distance of separation between the charges. It can be used to measure the size of dipole.

vick5821

不明白叻。。。。

qwer0909

想问一下两个题目～
KA1= hydrated iron(ll) sulphate, FeSO4(7H2O）， 30.0g, the solution was then made up to 1dm3 by adding dilute sulphuric acid and distilled water

KA2= solution containing 2.38g dm-3 manganate (vll)ions

titre value=20.6

1)calculate the mass of iron(ll) ions in 1dm3 of KA1
2)calculate the percentage of iron(ll) ions in FeSO4(7H2O）that was oxidised.
麻烦解释一下，谢谢谢谢～

piggiek

1. A small petrol car use octane as a fuel and it needs 3.6x10^4 kJ totravel 100 km. Calculate the cost of petrol consume per kilometre[Standard heat of combustion of octane = -5470 kJ mol-1; density ofoctane = 0.66 g mL -1 ; cost of octane = RM 1.85 L -1]

2. 6 dm3(mixture at room conditions) of a mixture of propane and butane oncomplete combustion rises 10kg of water through 15.6 celcius. Calculatethe percentage composition of the mixture by volume [Standard heat ofcombustion for (i) propane = -2220 kJ mol-1 (ii) butane = -2877 kJmol-1]

JianWen

1. Is Ionic componf always has giant lattice sturcture?
2.two glass bulbs of volume 200cm3 and 500cm3 contain helium gas of pressure 5Pa and nitrogen gas pressure 10Pa respectively.If the clip is removed,what will be the pressures in the bulbs? [Ans:8.6Pa, Q:8.6Pa]
3.Which of the following causes deviation frm ideality?
i)molecules are not point masses
ii)temperature close to its boiling point
iii)Molecules stick during collisions

JianWen

1. Is Ionic componf always has giant lattice sturcture?
2.two glass bulbs of volume 200cm3 and 500c ...
JianWen 发表于 13-8-2010 07:55 PM

    Glass P - 500cm3,Nitrogen gas, 10Pa
    Glass Q - 200cm3,Helium gas,5Pa

wennn

pls help me to solve, thx~~~
1. 100cm^3 of aqueous silver nitrate is added to 100cm^3 of 0.2 mol dm^-3 potassium chloride. what is the minimum concentration of silver nitrate, in mol dm^-3, that is required to precipitate silver chloride? (solubility product of silver chloride is 2.0x 10^-10 mol^2 dm^-6

2.the solubility of cadmium hydroxide in water at 25C is 1.0x10^-5 mol dm^-3. what is the numerical value for its solubility product at 25C?

Hanix

想问下那个chapter可以不必那么focus的？

silent91

想问下那个chapter可以不必那么focus的？
Hanix 发表于 20-8-2010 09:31 AM

    看你是想及格还是想A～

Hanix

是要A的。。。
就是问看那个可以放松点的。。。
因为我是私人考生。。。不是很了解。。。不好意思。。。

silent91

是要A的。。。
就是问看那个可以放松点的。。。
因为我是私人考生。。。不是很了解。。。不好意思。。 ...
Hanix 发表于 20-8-2010 09:45 PM

    要A的话，基本上每个都很重要。。。个人觉得inorganichem可以比其他放松一点点～

PS：我也是今年的考生～

Hanix

感激...

多多指教....加油了...

vick5821

Consider the dissociation of dinitrogen tetroxide in chloroform(trichloromethane)
N2O4 ---><--- 2NO2

Describe and explain what would happen if chloroform is added to the system in equilibrium. Chloroform acts as solvent..

How ar?

vick5821

Got one ques here

1.0 mol each of CO and Cl2 are introduced into a evacuated 1.75L flask. At equlibrium, the total pressure of the gaseous mixture is 32.4atm. Calculate Kp

CO(g) + Cl2(g) --><--- COCl2(g)

How ar?? any hint??thanks ^^

silent91

Got one ques here

1.0 mol each of CO and Cl2 are introduced into a evacuated 1.75L flask. At equl ...
vick5821 发表于 31-8-2010 09:17 AM

  calculate num of mole, then find partial pressure of each molecule...
then u canfind Kp...(i guess)

數學神童

the Mn atom in MnO4- ion has no electron in d-orbital.Why is it still gives purple colour since there is no d-d transition?

nkrealman

The color in KMnO4 arises from an electronic transition, but it is actually not a d-d transition, since the Mn in this compound has no d electrons. It arises from a charge transfer reaction within the molecule, in which photons promote an electron from the highest energy molecular orbital in one of the Mn-O bonds to an empty d orbital on the manganese. This promotion is equivalent to the energy of a yellow photon, so yellow light is absorbed leaving us to see purple, the complementary color.

MnO4- : The permanganate ion having tetrahedral geometry is intensely purple due to strong absorption involving charge transfer from MO derived primarily from filled oxygen p orbitals to empty MO derived from manganese(VII).

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