Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: submar1ney on January 20, 2008, 10:33:33 AM
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Given a beaker of dilute hydrochloric acid of which 12g is pure hydrochloric acid, and i add a crystal of calcite (calcium carbonate) of mass 18g, is it possible to find the mass of calcite left after the reaction is finished? If so, how?
Thank you
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You are given: 12 g HCl + 18g CaCO3
1. Write out your reaction equation:
CaCO3 + HCl → CaCl2 + CO2 + H2O
2. Balance your reaction equation:
CaCO3 + 2HCl → CaCl2 + CO2 + H2O
3. Remember that species react mole to mole and NOT gram to gram.
4. Then you use your balanced reaction equation and find the grams of calcite left upon the completion
of the reaction. Which means UNREACTED or EXCESS calcite (calcium carbonate).
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You are given: 12 g HCl + 18g CaCO3
1. Write out your reaction equation:
CaCO3 + HCl → CaCl2 + CO2 + H2O
2. Balance your reaction equation:
CaCO3 + 2HCl → CaCl2 + CO2 + H2O
3. Remember that species react mole to mole and NOT gram to gram.
4. Then you use your balanced reaction equation and find the grams of calcite left upon the completion
of the reaction. Which means UNREACTED or EXCESS calcite (calcium carbonate).
I have already balanced it correctly, but don't understand where to go from your point 3. Can you elaborate please.
Cheers
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You know the moles of HCl used. From the reaction equation you know how many moles of calcite are needed to react with this amount. Convert your result to grams and substract it from the initial mass of calcite.
I hope the information helps you.
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http://www.chembuddy.com/?left=balancing-stoichiometry&right=stoichiometric-calculations
http://www.chembuddy.com/?left=balancing-stoichiometry&right=limiting-reagents
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OK, so 1 mole of HCl = 36.51g so 2 moles = 73.02g... 12g/73.02g = 0.16 moles of HCl
1 mole of CaCO3=100g... 18g/100g = 0.18 moles of CaCO3
From there then, i take 0.16 moles from 0.18 moles to give 0.02 moles??? How does that convert to grams?
Cheers
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You have 12 g HCl How many moles are this? And with how much calcite can it react?
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You have 12 g HCl How many moles are this? And with how much calcite can it react?
I thought 1 mole of a compound was the relative molecular mass, in grams?
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You have 12 g HCl How many moles are this? And with how much calcite can it react?
I thought 1 mole of a compound was the relative molecular mass, in grams?
Molar mass doesn't depend on the reaction, it is characteristic of compound.
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http://en.wikipedia.org/wiki/Molecular_mass
(http://www.forkosh.dreamhost.com/mimetex.cgi?n(HCl)=\frac{m(HCl)}{M(HCl)})
Does that help to calculate the moles of HCl?
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No sorry guys, i'm not with you.
My book say to calculate moles, write the formula.. HCl... and add the relative atomic masses. (not molecular mass as i previously quoted, my mistake). So, H=1.01 + Cl=35.5 = 36.51 grams - 1 mole.
No???
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M=molar mass
(http://www.forkosh.dreamhost.com/mimetex.cgi?M(HCl)=M(H) + M(Cl)=1.0079\frac{g}{mol}+35.4532\frac{g}{mol}=36.4611\frac{g}{mol})
(http://www.forkosh.dreamhost.com/mimetex.cgi?n(HCl)=\frac{m(HCl)}{M(HCl)}=\frac{12g}{36.4611\frac{g}{mol}}=0.33 mol)
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M=molar mass
(http://www.forkosh.dreamhost.com/mimetex.cgi?M(HCl)=M(H) + M(Cl)=1.0079\frac{g}{mol}+35.4532\frac{g}{mol}=36.4611\frac{g}{mol})
(http://www.forkosh.dreamhost.com/mimetex.cgi?n(HCl)=\frac{m(HCl)}{M(HCl)}=\frac{12g}{36.4611\frac{g}{mol}}=0.33 mol)
So 2 lots of HCl will be 0.16 moles... which is what i calculated earlier in the thread :-) But where do i go from here to calculate how much calcite will be left over :-)
Thank you :-)
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Once again:
http://www.chembuddy.com/?left=balancing-stoichiometry&right=stoichiometric-calculations
Please read how to read balanced reaction equation. That's the key for all stoichiometric calculations.
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But I don't believe you knew what you did before ;)
So now you know that 0.33 mol react with 0.16 mol calcite. What you want to determine next is how many moles of calcite remain. Then determine the mass that remains. I am sure you can do that on your own now. :)
EDIT
And please read the link Borek posted. It will help you to do further calculations on your own.
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From there then, i take 0.16 moles from 0.18 moles to give 0.02 moles??? How does that convert to grams?
Sorry I haven't read this. The answer is correct. Conversion to mass is easy: m=M*n
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Ok guys, here's what i get from a similar example.
Given 12.6g of 2HNO3 and 15g of CaCO3, how much CaCO3 is left after the reaction is over.
2 moles of 2HNO3=126.02g and 1 mole of CaCO3 = 100.1g
100.1 : 164.1 = 15g : x
x = (100.1 / 126.02) x 12.6g = 10g of CaCO3 left over???
Hope so...
Cheers
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15g - 10 g (0.1 mol) = 5 g left over...
assuming that you start with 12.6 g HNO3
if you start with 6.3 g you are right.
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x = (100.1 / 126.02) x 12.6g = 10g of CaCO3 left over???
Kryolith already gave you the final answer - you made small mistake. You have CORRECTLY calculated mass of calcium carbonate that REACTED. You have just forgot the final step.
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Ah so what i calculated is the amount used in the reaction?
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Ah so what i calculated is the amount used in the reaction?
Exactly :)
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Ah so what i calculated is the amount used in the reaction?
Exactly :)
Ok... just to clear up my confusion.. hahaha I calculated the amount of CaCO3 used in the reaction, so subtract this from the original amount of 15g i'm left with 5g of CaCO3?
I love chemistry :P
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15g - 10 g (0.1 mol) = 5 g left over...
Congratulation. You got it! :)
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:) thanks for all your help guys ;-)
Have a good night.
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Very god job all.
5 scooby snacks given to Kryolith, Borek and Alpha-Omega.