Calorimetery Problem. It's not a homework but I can't get the answer.

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Discussion Overview

The discussion revolves around a calorimetry problem involving the combustion of ethanol in a flame calorimeter. Participants are exploring the calculation of the change in enthalpy for the combustion process and the heat released for a specific mass of ethanol. The scope includes mathematical reasoning and technical explanation related to thermodynamics and calorimetry.

Discussion Character

  • Technical explanation, Mathematical reasoning, Debate/contested

Main Points Raised

  • One participant presents a calorimetry problem involving the combustion of 0.510 g of ethanol and the resulting temperature change in water.
  • Another participant requests a solution attempt and relevant equations to aid in understanding.
  • A participant shares their calculation approach using the equation Q(rxn) = Q(water) + Q(calorimeter) and provides a detailed breakdown of their calculations, arriving at a value of 47.22 kJ.
  • One participant questions the calculated value, asking for clarification on the enthalpy value per gram or per mole of ethanol and notes the importance of the sign in the result.
  • Another participant encourages the original poster to consider equations that relate enthalpy and energy, suggesting further exploration of the topic.

Areas of Agreement / Disagreement

Participants appear to agree on the initial approach to the problem, but there is no consensus on the final value or the proper expression of the enthalpy change. The discussion remains unresolved regarding the correct interpretation and final calculations.

Contextual Notes

There are limitations in the provided calculations, including potential missing assumptions about the system and the need for clarity on units and signs in thermodynamic equations.

Who May Find This Useful

This discussion may be useful for individuals interested in calorimetry, thermodynamics, and the calculation of enthalpy changes in chemical reactions.

Owelode
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Calorimetery Problem. :( It's not a homework but I can't get the answer.

0.510 g of ethanol is burned in a flame calorimeter (constant pressure) containing 1200 g of water. The water is initially 22.46 C and is warmed up to 25.52 C as a result of the reaction. The heat capacity of the calorimeter is 10.4 kJ/ C. What is the change in enthaply for the combustion of ethanol? Also, calculate the heat released when 73.5 g of ethanol undergoes combustion.
 
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Show an attempt at a solution? Relevant equations? Anything?
 


I did attempt it on my own. I was hoping someone would explain it to me though.


I used Q(rxn) = Q(water) + Q(calorimeter)

Also expanded: Q (rxn) = -[(m*s*change in temp.) + (C*change in temp.)]
= -[(1200*4.184*3.06) + (10400*3.06)] <---- I changed things from joules to kJ

And then I am lost from there. I got 47.22 KJ
 


Seems to me so far you are doing fine. 47.22kJ per how much ethanol? It will be better to list it either per gram or - even better - per mole. And watch the sign.

--
 


Your solution looks good so far, you're almost there. What equations do you know that include enthalpy and energy?
 

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