Author Topic: IGCSE CHEMISTRY DOUBTS HERE !!!!  (Read 24031 times)

Offline Vin

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #45 on: January 12, 2011, 07:02:42 am »
I hope I'm right.

1. Ce = 140g

n = 4.2/140
=0.03 moles

2. 5.16 - 4.2 = 0.96 g

3. moles of O2

n = 0.96/ (16+16)
= 0.03 moles

4. ratio = 1:1

5. Ce + O2 ---> CeO2

Formula = CeO2

Offline ~Dazzling Star~

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #46 on: January 12, 2011, 07:50:07 pm »
I hope I'm right.

1. Ce = 140g

n = 4.2/140
=0.03 moles

2. 5.16 - 4.2 = 0.96 g

3. moles of O2

n = 0.96/ (16+16)
= 0.03 moles

4. ratio = 1:1

5. Ce + O2 ---> CeO2

Formula = CeO2
hmmmm,i think it should be done like this :
1 . n=m/Mr
     n=4.2/75
     n=0.056 moles
2 . mass of reacted Oxygen=5.96-4.2=0.96g
3 . n=m/Mr
     n=0.96/(16*2)=0.03 moles
4 . 0.056:0.03=2:1
5 . CeO
do u agree?

Offline Vin

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #47 on: January 13, 2011, 10:30:28 am »
Hmm I think the Mr for Ce is 140g in the periodic table. :/ atomic number 58

Offline Most UniQue™

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #48 on: May 24, 2011, 07:11:07 am »
M/j 2005 p62 Q8

Plz help got exam tomorrow Thanks in advance:D

Offline The Golden Girl =D

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #49 on: May 24, 2011, 07:12:28 am »
can ya give me a link of the paper.
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Offline The Golden Girl =D

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #51 on: May 24, 2011, 07:33:38 am »
M/j 2005 p62 Q8

Plz help got exam tomorrow Thanks in advance:D

I'll give you the General Idea behind it.

You put a known amount of hydrogen peroxide in a test tube  that is connected to a gas syringe and burn the test tube/allow the powder inside it to decompose ... for certain time intervals ex every 1 minute record the time and the volume of gas collected

the one the gave out the most gas in the same period of time is the best catalyst.

I hope I helped :)
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Offline Most UniQue™

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #52 on: May 24, 2011, 07:46:00 am »
I'll give you the General Idea behind it.

You put a known amount of hydrogen peroxide in a test tube  that is connected to a gas syringe and burn the test tube/allow the powder inside it to decompose ... for certain time intervals ex every 1 minute record the time and the volume of gas collected

the one the gave out the most gas in the same period of time is the best catalyst.

I hope I helped :)

Oh okaaa tnxxx!!!! ;D ;D

Offline Most UniQue™

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #53 on: May 24, 2011, 07:49:43 am »
and By the way for the same paper,q6c, should i draw a chromatograph or explain?

Offline The Golden Girl =D

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #54 on: May 24, 2011, 08:16:05 am »
and By the way for the same paper,q6c, should i draw a chromatograph or explain?

Explain but Whenever I had chromatography exps , My teacher used to say that we have to draw and explain.
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Offline Most UniQue™

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #55 on: May 24, 2011, 09:31:36 am »
Explain but Whenever I had chromatography exps , My teacher used to say that we have to draw and explain.

they havent given any lines for writing,they have just given a blank space so r u sure?

Yah in the other they give both line and blank space for both drawing and writing

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #56 on: May 24, 2011, 09:33:33 am »
I'm not sure .
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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #57 on: May 24, 2011, 09:56:14 am »
I'm not sure .

ok By the way for the same question i should only show a drop of jam on the starting line and the spots which appear or i should also include 2 or 3 drops of other colours on the starting line also?

Thanks and sryt fr askign too many questions:D want to be sure:D:

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #58 on: May 24, 2011, 11:49:47 am »
ok By the way for the same question i should only show a drop of jam on the starting line and the spots which appear or i should also include 2 or 3 drops of other colours on the starting line also?

Thanks and sryt fr askign too many questions:D want to be sure:D:

It's  lemon drink ... Put a Drop at the starting line and a 2 drops since it's made of two colorings.
« Last Edit: May 24, 2011, 11:52:23 am by ~ Miss Invisible ~ AKA GG »
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Offline Most UniQue™

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Re: IGCSE CHEMISTRY DOUBTS HERE !!!!
« Reply #59 on: May 24, 2011, 03:48:26 pm »
It's  lemon drink ... Put a Drop at the starting line and a 2 drops since it's made of two colorings.

ok got it:D