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Chemistry / How are partial pressures of gases calculated?

« on: 22/05/2005 05:08:18 »

1.) A container contains 60cm3 of CO2 and 40cm3 of O2 at room temperature and pressure conditions. If 200cm3 of H2 at room temperature and pressure is now injected into the container, which of the following would happen?[]
(a) The partial pressure of O2 will decrease
(b) The total pressure of the gases in the container will increase
(c) The partial pressure of CO2 and O2 remain constant
The answer given is (b) & (c),why?how to count?Please show the calculations.[]

2.) When a few crystals of ice are added to supercooled water at -5 degree Celcius,which of the following would happen?[]
(a) More ice is precipitated
(b) The vapour pressure increases
(c) The temperature of the water increases
The answer given is (a),(b)&(c),why?Please provide me some explanation.[:p]
   

2

Chemistry / Is there a method to determine the number of oxidation states for an element?

« on: 26/12/2004 15:25:18 »

Hello everyone.I wanna ask something about chemistry.[]

Is there a method to determine how many oxidation states that an element can exist?normally those can have more than one oxidation states is from the D-block element,such as copper(+2,+3) and titanium(+1,+2,+3,+4) and so on.[][]

I have no idea how to find out the number of oxidation states that an element can exist,for example nikel,is there anyone can help?[]

3

Chemistry / How do you calculate the melting point of water at different pressures?

« on: 21/12/2004 10:05:52 »

Given that the melting point of water at 218 atm is 1.61 Celcius degree,and at 1 atm,the melting point is 0 celcius degree.[][]

what is the melting point of water at 0.5 atm?can anyone show the calculation step by step?[][]

4

Chemistry / Re: melting point

« on: 20/12/2004 02:15:04 »

thanks alot to you all.[]
i think it is quite useful to me,thanks again for solving my problem.[][]

5

Chemistry / melting point

« on: 17/12/2004 09:40:47 »

If a thin wire with heavy weights at each end is placed over a block of ice, the wire rapidly cuts through the block of ice. I understand that an increase in pressure under the wire will lowers the melting point of ice, but why the wire will cut through? If the ice is replaced with dry ice, wire does not cut through the dry ice, is this also something to do with melting point?[?][][]

another question regarding to melting point also.Given that the melting point of water at 218 atm is 1.61 Celcius degree,what is the melting point of water at 0.5 atm?can anyone show the calculation step by step?[][]

I do know that my question is quite long, hope anyone that wishes to solve won't mind bout it,y our help will be most appreciated.[:p]