richard thomas
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| posted on 22/1/12 at 08:56 PM |
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Homework question.....
....I know some of you on here will know the answer to this....but been a long time since my GCSE Chemistry....
Sure my daughter will work this out anyway in her own time, but for my own sanity.....does anyone know...
'How many Kg of limestone is needed to make 100Kg of CaO?'
Any takers? and if you could explain to me how you got there that would be cool....cos my daughter is confusing me with description of 'balanced
equations, and theoretical and percentage yield'.....bloody sure that wasn't in my exams....and it wasn't that long ago that science
has moved on since then, i am sure.....
(my daughter has come to the conclusion that the answer is 178.57kg.....i hope she is correct......)
[Edited on 22/1/12 by richard thomas]
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MakeEverything
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| posted on 22/1/12 at 09:09 PM |
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No idea if this is correct, but those that have worked this out before will know if it is;
http://uk.answers.yahoo.com/question/index?qid=20100911063652AALLaUL
Certainly has the same answer (Problem 8).
[Edited on 22-1-12 by MakeEverything]
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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richard thomas
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| posted on 22/1/12 at 09:11 PM |
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Spot on....thank you!!
Rich.
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Ninehigh
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| posted on 22/1/12 at 09:14 PM |
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I've no idea of the composition of limestone, but CaO is going to be a nice split 50/50
If limestone is CaX.. Then half of the limestone goes to making the Ca for the CaO (so you need 200kg?)
If limestone is CaXY (or X2Ca and so on) that half is now a third so 300kg
That's how I remember it anyway
Just as a thought though if limestone is Ca2X then you need 100kg
If there's any O in the limestone that counts in there too in the same way (30kg of CaOX will make 20kg of CaO because X represents a third)
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richard thomas
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| posted on 22/1/12 at 09:22 PM |
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Led to believe that the answer is indeed 178.57 kg....clever girl.....hope she passes and earns enough to see me into early retirement...least she can
do for 'our' help in her homework.....
[Edited on 22/1/12 by richard thomas]
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Dave Ashurst
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| posted on 22/1/12 at 09:27 PM |
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quote:
Originally posted by richard thomas
....I know some of you on here will know the answer to this....but been a long time since my GCSE Chemistry....
Sure my daughter will work this out anyway in her own time, but for my own sanity.....does anyone know...
'How many Kg of limestone is needed to make 100Kg of CaO?'
Any takers? and if you could explain to me how you got there that would be cool....cos my daughter is confusing me with description of 'balanced
equations, and theoretical and percentage yield'.....bloody sure that wasn't in my exams....and it wasn't that long ago that science
has moved on since then, i am sure.....
(my daughter has come to the conclusion that the answer is 178.57kg.....i hope she is correct......)
[Edited on 22/1/12 by richard thomas]
I get 178.48 kg
but 178.57 is OK
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hughpinder
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| posted on 23/1/12 at 09:42 AM |
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limestone decomposing to CaO +C02 is not a reversible reaction, so assume 100% conversion
First work out how may kg of Ca there are in 100 kg of CaO using proportions
Ca molecular wt = 40, O = 16
so the proportion by weight of the CaO that is Ca = (Ca molecular weight)/(CaO molecular weight) = 40/(40+16) = 0.7142 (or 71.42% if you like)
therefore 100 kg of CaO contains 71.42 kg of calcium.
So how much limestone (CaC03) do you need to get 71.42 kg of Ca?
CaC03 molecular weight is 40(Ca)+12(C)+3*16(O3) = 100 (conveniently), of which 40 is Ca.
so 40/100 of the weight you want is 71.42kg.
40*(weight)/100 = 71.42
(weight) = 71.42*100/40 = 178.57kg
I hope that makes it clearer, not less clear.
Note: Real molecular weights are never quite the exact whole numbers used here, but that wont be an issue up to about A level!
Regards
Hugh
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bobinspain
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| posted on 23/1/12 at 09:57 AM |
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quote:
Originally posted by hughpinder
limestone decomposing to CaO +C02 is not a reversible reaction, so assume 100% conversion
First work out how may kg of Ca there are in 100 kg of CaO using proportions
Ca molecular wt = 40, O = 16
9.5/10 Hugh.
Ca atomic weight is 40.
O atomic weight 16.
CaO molecular weight is thus 56.
Everytrhing else is bang on. (I think). It's 47 years since I did this stuff.
Regards, Bob.
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hughpinder
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| posted on 23/1/12 at 10:34 AM |
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You are right - should have been atomic weight not molecular weight - Bah, its only 30 years since I last did it too!
Regards
Hugh
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