How Does Heat Release Affect Water Temperature in Thermochemical Reactions?

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SUMMARY

The discussion centers on calculating the final temperature of water after a thermochemical reaction that releases 90 kJ of heat. The correct formula to use is q = mc(delta T), where q represents heat, m is the mass of water, and c is the specific heat capacity. The participant initially miscalculated by using incorrect values, including an erroneous heat value of 400 kJ instead of 90 kJ and incorrect units for specific heat capacity. The final temperature can be accurately determined by using the correct values and units in the equation.

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  • Understanding of thermochemical reactions
  • Familiarity with the formula q = mc(delta T)
  • Knowledge of specific heat capacity in J/(g K)
  • Basic principles of heat transfer
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  • Review the concept of specific heat capacity and its units
  • Practice calculations involving q = mc(delta T) with different substances
  • Explore thermodynamic principles related to heat release in reactions
  • Investigate common mistakes in thermochemical calculations and how to avoid them
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Students studying chemistry or physics, particularly those focusing on thermodynamics and heat transfer in chemical reactions.

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I know this is a physics forum, but this problem is mainly physics, and exceedingly simple:

Homework Statement



A certain reaction releases about 90 kJ of heat when stoichiometric amounts of reactants react. If the reaction goes to completion in 100 g of water whose initial temperature is 20 deg C, what is the final temperature of the water?


Homework Equations



q = mc(delta T), I believe, so delta T = q / (mc)

The Attempt at a Solution



I don't know what I'm doing wrong, but if I plug the 400 kJ = 400000 J into q and the 100 g mass into m and 4.184 J / (mol deg C) into c, I get an insane change in temperature around 215 degrees. I am obviously forgetting some step or misunderstanding something... I've always had trouble with thermodynamics stuff like this. Any help would be greatly appreciated.. thank you!
 
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Firstly should q not be 90kJ. Secondly the units of c that you provide are J/(g K). Other than that your calculations seem fine.
 

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