Delta H for 25.0 g NaOH in 100ml of 31.5% HCl

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Discussion Overview

The discussion revolves around calculating the change in enthalpy (delta H) for the reaction between 25.0 g of NaOH and 100 ml of 31.5% HCl, given a temperature change of 6.2 degrees Celsius. The context includes a homework problem involving thermochemical calculations in an aqueous environment.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant proposes using the equation Q = mcΔT to calculate delta H, where m is mass, c is the specific heat capacity of water, and ΔT is the temperature change.
  • Another participant agrees with the general approach but challenges the assumption of using the specific heat capacity of water, noting that 31.5% HCl is not a diluted solution and that this assumption may not be valid for concentrated solutions.
  • A later post questions how to calculate delta H without a value for mass when mixing two aqueous solutions.

Areas of Agreement / Disagreement

Participants generally agree on the approach to use the heat equation but disagree on the appropriateness of using the specific heat capacity of water for the concentrated HCl solution. The discussion remains unresolved regarding the calculation of delta H without a mass value.

Contextual Notes

There are limitations regarding the assumption of specific heat capacity for concentrated solutions and the lack of mass value for the calculation.

Jan Hill
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Homework Statement


How do I calculate delta H given the above info and knowing the specific heat capacity of
H2O and that the change in temperature when the 2 react is 6.2 degrees C


Homework Equations





The Attempt at a Solution



Using Q = mcdeltatheta where
m=mass and
c=specific heat capacity of H2O (Using H2O's specific heat capacity because there is an aqueous environment here)
delta T - 6.2 degrees C
Finding Q then substituting in for deltaH = m x delta T x Q
Is this the right way to go about finding delta H for this problem?
 
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Yes and no. Yes - that's the corect approach. No - assumption that you should use specific heat of water is in general wrong, as it works reasonably well for diluted solutions, 31.5% HCl is not diluted (10M), adding 25.0 g of NaOH won't dilute it much. But if you have no access to tables of specific heat as a function of solution concentration, this assumption is better than nothing.

--
 
Thank you
 


In this case, mixing 2 aqueous solutions, how would I calculate delta H without a value for mass?
 

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