Solving Mass Loss: Beginner Chem Student Struggling

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Discussion Overview

The discussion revolves around a beginner chemistry student's struggle with understanding mass loss during a chemical reaction involving a mystery metal and hydrochloric acid (HCl). The student seeks to determine the mass and moles of carbon dioxide (CO2) released during the reaction, as well as the experimental molar mass of the metal carbonate produced. The scope includes experimental calculations and chemical equations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant suggests starting with a fully balanced equation for the reaction but acknowledges the challenge of identifying the unknown metal.
  • Another participant proposes calculating the moles of HCl using its molarity and volume, and then writing the balanced equation to determine the amount of CO2 released.
  • The student outlines specific calculations needed, including finding the mass and moles of CO2 released, and determining the experimental molar mass of the metal carbonate (M2CO3).
  • There is a mention of weighing the graduated cylinder before and after adding HCl, leading to confusion about how this data fits into the calculations of mass loss and CO2 production.
  • The student speculates that the difference in mass might indicate the amount of CO2 lost during the reaction, but expresses uncertainty about the calculations leading to this conclusion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct approach to the calculations or the implications of the mass measurements. Multiple competing views and uncertainties remain regarding the identification of the metal and the calculations involved.

Contextual Notes

The discussion highlights limitations in the student's understanding of the relationship between the mass of reactants and products, as well as the need for a balanced chemical equation, which remains unresolved due to the unknown metal.

Who May Find This Useful

Students and educators in introductory chemistry, particularly those dealing with stoichiometry and mass loss in chemical reactions.

ecoonrod
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I am beginner chem student and I am lost with mass loss. We did an experiment in lab where we are trying to identify a mystery metal. let me describe. We weighed our flask, then weighed our flask with about 1.5g of the mystery metal. Then we added 20ml of 6M HCl to a graduated cylinder and added that to the flask of metal. Then we weighed the empty graduated cylinder. and the flask with the final solution. Now for the question. I need to determine the mass and moles of CO2 released. where do I start? I was thinking that I would figure out the moles of HCl but then i realized that I don't think that is right. I think it has something to do with the mass of the graduated cylinder when full and empty but that is is grams of HCl. HELP !
Ellie
 
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Let's start out with the fully balanced equation for the reaction you are considering.
 
how do I get a fully balanced equation if I don't know one of the elements? as a matter of fact the last question is "Using your identification of the metal write a balanced equation for the reaction that occurs ..."
 
okay here are the questions so you see what I need:
1. Clearly show the following calculation of the experimental molar mass of the alkali metal from the recorded data of one of your trials. Identify all numbers and units.
a. Find the mass of CO2 released.
b. Find the number of moles of CO2 released. (This is the same as the number of moles of M2CO3 needed to produce the amount of CO2.)
c. From the mass and moles of M2CO3 find the experimental molar mass of M2CO3.
d. Using the molar masses of carbon and oxygen from the periodic table, find the experimental molar mass of the metal.
Ellie
 
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Hello, you may try multiplying the molarity and volume of [itex]\displaystyle HCl[/itex] to learn how many moles (or millimoles) are there. Then write the balanced equation between [itex]\displaystyle M_2CO_3[/itex] and [itex]\displaystyle HCl[/itex], to learn how much [itex]\displaystyle CO_2[/itex] is released. You may use this info:
[itex]\displaystyle metal~carbonates~give~CO_2,~H_2O,~and~metal~chloride~with~HCl[/itex]
If you can learn how many moles of [itex]\displaystyle CO_2[/itex] is produced, than you can convert it to the moles of [itex]\displaystyle M_2CO_3[/itex], from here, the molar mass by calculating some proportions (1 mole of compound would be x grams, but I have n moles of compound, so I have y grams of that compound, etc.). The only task after doing these will be subtracting the molar masses of carbon and oxygen from the compound.
 
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okay so if I do that then I it is (6M/1L)(20ml/1000L)= .12 moles
What I was thinking though is then why do they have us weigh the full cylinder and then the empty cylinder? because then I get 20.586 g of HCl used and I am not really sure where that is coming into play? My other thought was thst maybe it would be the weight of the flask with the metal + the amount in grams of HCl used= 122.56g but the final weight of the flask was 122.184. Which would mean taht .376g were lost as CO2??maybe.
 
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