# Chemistry Question HelpWatch

Thread starter 2 years ago
#1
The equation for the reaction is

CaCO3(s) → CaO(s) + CO2(g)
Calculate the maximum mass of calcium oxide that can be obtained by
heating 25 tonnes of calcium carbonate.
(Relative atomic masses: C = 12, O = 16, Ca = 40)

[The answer is 25 (tonnes) gives 56x25 (tonnes)]

But I don't understand the method to work it out!!!
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Thread starter 2 years ago
#2
BUMP!!!!!!!
0
2 years ago
#3
Use mass= moles x mr.

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2 years ago
#4
Mr of caco3= 100
Mr of cao= 56
Mass of caco3= 25,000,000g
Just plugin values

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0
2 years ago
#5
Tell me if you want the full explanation.

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Thread starter 2 years ago
#6
(Original post by Nurne)
Use mass= moles x mr.

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What's Mr?
Could you fully explain thanks.
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2 years ago
#7
Mr is the formula mass, you work that out first and then you pick out the ratio of molecules for each element (These are the first steps, i'm not sure what to do after that, good thing the exams at 1:30!)
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2 years ago
#8
I did this and got the answer of 14, where did you get it from?
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2 years ago
#9
25,000,000/100= moles of caco3
Moles of caco3 is 250,000
Ratio of caco3 to cao is 1:1
Therefore multiply moles by mr of cao to get mass of cao.

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2 years ago
#10
(Original post by jazz_xox_)
I did this and got the answer of 14, where did you get it from?
Yup.

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2 years ago
#11
(Original post by Nurne)
It says tonnes.

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how do you change grams to tonnes are you expected to know this??
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2 years ago
#12
Ihttp://www.bbc.co.uk/education/guides/zysk7ty/revision/3

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Thread starter 2 years ago
#13
(Original post by Nurne)
25,000,000/100= moles of caco3
Moles of caco3 is 250,000
Ratio of caco3 to cao is 1:1
Therefore multiply moles by mr of cao to get mass of cao.

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(Original post by jazz_xox_)
I did this and got the answer of 14, where did you get it from?
Honestly so confused. Why are we using moles. Cant this question be done without moles?
This is from a past exam paper [Edexcel C2 March 2013]
http://qualifications.pearson.com/co...e_20130305.pdf

(Original post by noor.m)
Mr is the formula mass, you work that out first and then you pick out the ratio of molecules for each element (These are the first steps, i'm not sure what to do after that, good thing the exams at 1:30!)
Omg, just realised the exam was in the afternoon... O.O MORE TIME!
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2 years ago
#14
(Original post by jazz_xox_)
how do you change grams to tonnes are you expected to know this??
You are expected to know that the mass in the mass=moles x mr equation is grams and that 1 tonne is equal to 1,000,000 grams. I've done these sorts of question in my past papers.

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2 years ago
#15
Idk how the answer is 25 I keep getting 14, 56 x 0.25 is 14 anyway?
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2 years ago
#16
(Original post by Nurne)
You are expected to know that the mass in the mass=moles x mr equation is grams and that 1 tonne is equal to 1,000,000 grams. I've done these sorts of question in my past papers.

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could you please go through this question step by step?
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2 years ago
#17
(Original post by Proximo)
Idk how the answer is 25 I keep getting 14, 56 x 0.25 is 14 anyway?
yes this is what I am getting! i divided 100 by 4 to get 25, and did the same to 56 and it's 14. i know it's in tonnes but the conversion would be the same
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2 years ago
#18
(Original post by Nurne)
25,000,000/100= moles of caco3
Moles of caco3 is 250,000
Ratio of caco3 to cao is 1:1
Therefore multiply moles by mr of cao to get mass of cao.

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That still gives 14 not 25
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2 years ago
#19
(Original post by CorpusLuteum)
The equation for the reaction is

CaCO3(s) → CaO(s) + CO2(g)
Calculate the maximum mass of calcium oxide that can be obtained by
heating 25 tonnes of calcium carbonate.
(Relative atomic masses: C = 12, O = 16, Ca = 40)

[The answer is 25 (tonnes) gives 56x25 (tonnes)]

But I don't understand the method to work it out!!!
It's 14 tonnes

It can't be 25 tonnes because that's the mass of Calcium Carbonate

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0
2 years ago
#20
(Original post by CorpusLuteum)
Honestly so confused. Why are we using moles. Cant this question be done without moles?
This is from a past exam paper [Edexcel C2 March 2013]
http://qualifications.pearson.com/co...e_20130305.pdf

Omg, just realised the exam was in the afternoon... O.O MORE TIME!
Dude! It's at 1:30, I should be sleeping but I just can't I have a feeling this paper will be hard Make sure to revise soluble salts! I heard that will be the 6 marker
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