Hi, I need some help in as chem, its quite urgent, its about moles...read inside... Watch

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~NC~
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#1
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Right im doing the salters course and im on the first excercise in the book chemical ideas, 1.1! Im stuck on question 14.
This is what the question says:
Calculate how many moles of each substance are contained in:
then it has a list eg: a 88g of carbon dioxide.

How do i work this out, is there a formula or anything i should know about??
Please help.
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john171
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#2
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Havent you done this at GCSE level?
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~NC~
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#3
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I probably have but i just cant remember it, im having the same problem that other person did about qu 13, it seems harder than it thinks! I really need some help.
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john171
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Wtf, if you done this YOU WOULD REMEMBER IT. It's drummed into you at GCSE level....
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~NC~
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#5
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Well i obviously didnt do it then, in that case can you help me, it may be there it just may need to be refreshed.
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Candy_Shop
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(Original post by Nutchopper)
Right im doing the salters course and im on the first excercise in the book chemical ideas, 1.1! Im stuck on question 14.
This is what the question says:
Calculate how many moles of each substance are contained in:
then it has a list eg: a 88g of carbon dioxide.

How do i work this out, is there a formula or anything i should know about??
Please help.
Ok seen as im doing the same thing right now .... i'll tell you what I put down, someone will have to confirm if this is right (will be useful)

Molecular mass of CO² = 44 (half of 88 so ya need to double em)
C= 24g
O² = 64g

moles for C = 24/12
and for O² = 64/32

so 2 moles each. Somebody tell me I'm correct? :confused:
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john171
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m=nxmr is the most basic equasion, then you got all the other crap like n=v/24 (involving gas laws and something or other) . Remember to use real and actual ratios also, and just re-arrange m=nxmr and you can get anything.....
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~NC~
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#8
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Lol i hope that is right and sorry john i dont really understand you.
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john171
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n = no. of moles
m= mass
mr = r.a.m

Just look at your periodic table to get the Ram...and you've been given the mass..
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john171
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So No of moles = Mass x RAM
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~NC~
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#11
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Ok john thanks a lot! That should help me alot!
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john171
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#12
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ohh crap. lol sorry I mixed up equasion Mass = No of moles X RAM
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Candy_Shop
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#13
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(Original post by john171)
ohh crap. lol sorry I mixed up equasion Mass = No of moles X RAM
Had me a bit worried then, thought I might've done 8 pages of calculations wrong :eek:
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~NC~
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#14
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lol no problem, i just thought to anyone not doing chemistry this title must look quite funny!
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~NC~
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#15
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um, sorry i need help again! For one of the answers i got 0.03, do i just times it by 100?
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oxymoron
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(Original post by Nutchopper)
um, sorry i need help again! For one of the answers i got 0.03, do i just times it by 100?
err, hard to tell you if you don't post the question! :confused:
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~NC~
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#17
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Lol sorry the question is calculate how many moles of each substance are contained it:
d. 2.92g of sulphur hexafluoride, SF6
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~NC~
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#18
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I got 2.92/108 but that just gave me 0.0259.. which i rounded to 0.03, i was wondering do i times it?
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oxymoron
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#19
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(Original post by Nutchopper)
I got 2.92/108 but that just gave me 0.0259.. which i rounded to 0.03, i was wondering do i times it?
That's right ... 0.026 moles (to 2sf)
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~NC~
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#20
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Is that the asnwer, cos im sure you cant just get 0.026 of a mole, dont you have to have a whole one>
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