Can someone tell me why this method is wrong even though it seems logical?

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Discussion Overview

The discussion revolves around a homework problem involving the reaction of lithium hydroxide with carbon dioxide, specifically focusing on calculating the mass of carbon dioxide that can be absorbed by a given mass of lithium hydroxide. The scope includes mathematical reasoning and stoichiometric calculations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents a balanced chemical equation and attempts to calculate the mass of carbon dioxide absorbed by lithium hydroxide, expressing uncertainty about their method and seeking a systematic approach.
  • Another participant provides a calculation that suggests 919g of carbon dioxide can be absorbed, using a stoichiometric ratio of 2:1 between lithium hydroxide and carbon dioxide.
  • A third participant presents a different calculation resulting in 14.8g of carbon dioxide, which appears to be inconsistent with the previous calculations.
  • There is mention of a textbook answer of 920g, which raises questions about the accuracy of the participants' calculations.
  • One participant acknowledges a mistake in their calculation process and reflects on the importance of clarity in their approach.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct answer, as different calculations yield varying results. The discussion reflects uncertainty and differing interpretations of the stoichiometric relationships involved.

Contextual Notes

Participants express confusion over their calculations and the systematic approach to solving the problem. There are unresolved discrepancies in the calculations presented, and assumptions about unit cancellation are noted but not fully explored.

Who May Find This Useful

Students working on stoichiometry problems, particularly those involving gas absorption reactions, may find this discussion relevant.

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Homework Statement


Solid lithium hydroxide is used in space vehicles to remove exhaled carbon dioxide from the living environment by forming solid lithium carbonate and liquid water. What mass of gaseous carbon dioxide can be absorbed by 1.00kg of lithium hydroxide?



The Attempt at a Solution



First, I balanced out the equation with the reactants and products:

[tex]2LiOH+CO_2 \right arrow Li_{2}CO_{3}+H_{2}O[/tex]

Then I found the molar mass of LiHO to be: 23.949g/ mol LiHO

So then I did this:

[tex]\frac{23.949g}{mol \\LiHO} \times \frac{2mol LiHO}{1molCO_{2}}=\frac{47.898g}{1molCO_2} \times \frac{1molCO_2}{44.01g}[/tex]

Other than that the units cancel out.. can someone tell me why it is wrong and how to avoid these problems? As of now, I just try to cancel the units out to get grams but I don't really have a "systematic" way of doing things. Is there a a systematic way? How do avoid not knowing what you are doing and how to arrive at the right answer? Thanks.
 
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[tex]1000g LiOH \frac{(12.01+32.0)g CO_2}{2(6.941+16.0+1.01)g LiOH} = 919g CO_2[/tex]

?
 
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rocophysics said:
[tex]1000g LiOH \frac{(12.01+32.0)g CO_2}{2(6.941+16.0+1.01)g LiOH} = 14.8g CO_2[/tex]

?

My book says the answer is 920g.
 
lLovePhysics said:
My book says the answer is 920g.
lol damn I'm way off, ok let me check

EDIT: ok i obviously shouldn't calculate in the dark, lol

i got 919g CO2

since you have a 2:1 stoichiometric ratio between LiOH and CO_2. i assume bc like to avoid writing too much, so i skip out on the moles and assume they cancel out nicely and just stick to the units that i am required in my answer.
 
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