Question regarding energy from chemicals (M.C.Q)

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Discussion Overview

The discussion revolves around a chemistry problem involving the thermal energy changes during a neutralization reaction between sodium hydroxide and hydrochloric acid. Participants analyze the relationship between the volumes of reactants used and the resulting temperature changes, exploring the implications of varying concentrations and volumes on the energy released during the reaction.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that the temperature rise T1 from the full volume reaction is half the temperature rise T2 from the reduced volume reaction, proposing that T2 is half the value of T1.
  • Another participant counters that while the volume is decreased, the total energy of the reaction is also decreased proportionally, indicating that cutting the number of moles of reactants in half results in half the total energy liberated.
  • A request for further explanation and examples is made to clarify the reasoning behind the energy calculations.
  • A proposal is made to calculate the energy liberated in both scenarios in terms of a variable Q, including the masses of the solutions and the ratio of energy to final mass for each case.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between the volumes of reactants and the resulting temperature changes, with no consensus reached on the correct answer to the original question.

Contextual Notes

Participants have not resolved the assumptions regarding the energy per mole of reactants and how this relates to the final temperature changes observed in the experiments.

Who May Find This Useful

Students and educators in chemistry, particularly those interested in thermodynamics and reaction energetics, may find this discussion relevant.

hamxa7
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Q. A volume of 100 cm3 of 1 mol dm3 sodium hydroxide solution was added to 100 cm3 of 1 mol dm3 hydrochloric acid.The maximum rise in temperature recorded was T1.The experiment was repeated with 50cm3 of each solution and the rise in temperature this time was T2. It is found That


A) T1 Is Equal To T2
B) T1 Is Half The value Of T2
C) T2 is half the value of T1
D) T2 Is a quarter the value of T1.


I think the Ans Should Be C as the volume is decreased...
What do you think as the answer given is A...

reply quickly... :-)
 
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The volume is decreased, but the total energy of reaction is decreased in proportion. Remember energies of reaction are per mole, so if you cut the number of moles of reactant in half, the total energy liberated is also cut in half.
 
can you explain it in further detail...
examples would be appreciated..
 
Assume 1 mole of NaOH reacting with 1 mole HCl liberates energy Q. Calculate how much energy is liberated in both cases (in terms of Q). Calculate masses of solution in both cases. Calculate ratio of energy liberated to final mass of the solution for each case (again in terms of Q, assume density of 1g/mL). What did you get?
 

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