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Author Topic: Chemistry Help HERE ONLY !!  (Read 106169 times)

Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #285 on: May 29, 2009, 02:31:31 pm »
Quote from: emi on May 29, 2009, 02:27:32 pm
lilwayne thanks but  i could have looked up the answers in MS too  :-X .. i wanna  know how to do it like an explanation would be more good



that is very insulting, lol , i didnt use no ms, i just did it on my own, before i typed it up for u, lol

so wat u have to do is revise moles all over again!!!
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Offline emi

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Re: Chemistry Help HERE ONLY !!
« Reply #286 on: May 29, 2009, 02:32:31 pm »
sry ,, i really suk at moles ..
so while solving could u also mention the formula you used .. so i can relate stuff together , and not just write the answers


thanks alot guys .. doubel +rep   =D

you guys rock the chemistry section
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Offline Shogun

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Re: Chemistry Help HERE ONLY !!
« Reply #287 on: May 29, 2009, 02:33:29 pm »
lol dnt wrry lil wayne is good with the moles..
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Offline emi

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Re: Chemistry Help HERE ONLY !!
« Reply #288 on: May 29, 2009, 02:34:15 pm »
i apologize if you find it insulting .  im sorry
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Offline ZeroZero82

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Re: Chemistry Help HERE ONLY !!
« Reply #289 on: May 29, 2009, 02:41:19 pm »
There are three formulas:
- n=m/Mr (moles = mass / molecular mass)
- n=V/24dm^3 ( moles = volume / 24 dm^3)
- n=CxV (moles = Concentration x Volume in dm^3)
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #290 on: May 29, 2009, 02:44:42 pm »
Quote from: emi on May 29, 2009, 02:34:15 pm
i apologize if you find it insulting .  im sorry

hahaha, im just messing around , alrigth then ill try my best to explain each part

number of moles of NiCO3 = 0.08 mols
cuz its says that the number of moles of sulphuric acid in 40cm3 of 2.0 mol/dm3 = 0.08 mol

and the reaction goes like this

NiCO3 + H2SO4 ---->  NiSO4  + CO2   +  H2O

only 1 mol of   NiCO3 reacted not 2 or 3 cuz if it was it would be : 2NiCO3 or anything else
and also 1 mol of H2SO4 reacted

so if 1 mol of H2SO4 is 0.08 (like it mentions) that means also 0.08 mol of nickel carbonate reacted
because it is 1:1 ratio

did u get the first part?
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Offline emi

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Re: Chemistry Help HERE ONLY !!
« Reply #291 on: May 29, 2009, 02:49:45 pm »
ahhaa ,, so because they want more i only have to see how much moles they have right ?
we can see that H2SO4 is one mole and its mole is 0.08 
so if NiCO3 is also one more then it will also be 0.08


right ?

tell me if i pass this part
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Offline emi

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Re: Chemistry Help HERE ONLY !!
« Reply #292 on: May 29, 2009, 02:52:39 pm »
but the Question says " an excess of nickle carbonate 12g was added to 40cm3 of sulphuric acid , 2 mol/dm3"

what do they mean by 2 mol/dm3

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Offline Shogun

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Re: Chemistry Help HERE ONLY !!
« Reply #293 on: May 29, 2009, 02:53:08 pm »
first,in qi) in the question was given tht 40 cm3 of 2.0 mole per dm cube of nickle carbonate
now use the equation concentration x colume in dm 3 to get the number of mole of nickle carbonate. but first the volume is given in cm3 u have to convert it by deviding by 1000 to dm3
so it wuld be: 40cm3/ 1000 = 0.04dm3
now use tht first formula 2 x 0.04= 0.08 moles

qii) here its cross multiplication so it would be like 1 mol gave u 119g how much would 0.08 moles give u?
so it would be :
no. of moles                      mass produced
       1                                    119
       0.08                                  ?

so 0.08 x 119= 9.52g

qiii)now they said total reacted was 12g but was in excess, and we found out tht 9.52g was really reacted so wat was left of it was the unreacte nickel carbonate. (i. subtraction)
so it would be : 12-9.52= 2.48g

now i)  ill explain it after i come back, srry i have to go some where, ill return in about 10 mins
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Offline Shogun

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Re: Chemistry Help HERE ONLY !!
« Reply #294 on: May 29, 2009, 02:54:22 pm »
Quote from: emi on May 29, 2009, 02:52:39 pm
but the Question says " an excess of nickle carbonate 12g was added to 40cm3 of sulphuric acid , 2 mol/dm3"

what do they mean by 2 mol/dm3



tht 2 is the concentration of nickel carbonate
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #295 on: May 29, 2009, 02:56:12 pm »
Quote from: emi on May 29, 2009, 02:49:45 pm
ahhaa ,, so because they want more i only have to see how much moles they have right ?
we can see that H2SO4 is one mole and its mole is 0.08 
so if NiCO3 is also one more then it will also be 0.08


right ?

tell me if i pass this part


yeah u passed this part and shogun 2 mol/dm3 is the conc of the H2SO4
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Offline Shogun

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Re: Chemistry Help HERE ONLY !!
« Reply #296 on: May 29, 2009, 02:58:52 pm »
yup, srry its the concentration od sulphuric acid,lol
lil wayne hos do i do get the maximum moles of hydrated salt....
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Offline Shogun

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Re: Chemistry Help HERE ONLY !!
« Reply #297 on: May 29, 2009, 03:04:25 pm »
cuz i could do 10.4/281, and i got 0.03 but whn i went and check the mark scheme it says 0.08, i cant seem to ge tht answer. i mean i now how to do the next ones but it would only dpend on this particular answer... ???
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one who masters both the pen and paper is indeed a true warrior.

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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #298 on: May 29, 2009, 03:06:40 pm »
Quote from: Shogun on May 29, 2009, 02:58:52 pm
yup, srry its the concentration od sulphuric acid,lol
lil wayne hos do i do get the maximum moles of hydrated salt....


its 0.08 cuz (1:1) ratio
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Offline unknown 101

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Re: Chemistry Help HERE ONLY !!
« Reply #299 on: May 29, 2009, 03:08:08 pm »
Quote from: LilWayne on May 29, 2009, 03:06:40 pm
Quote from: Shogun on May 29, 2009, 02:58:52 pm
yup, srry its the concentration od sulphuric acid,lol
lil wayne hos do i do get the maximum moles of hydrated salt....


its 0.08 cuz (1:1) ratio

the nickel sulphate from the past part was 0.08 mol so the hydrated salt would also be 0.08
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