Calculating Heat Released During Water Freezing

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SUMMARY

The calculation of heat released during the freezing of 12.4 g of water is determined using the heat of fusion, which is 6.02 kJ per mole. The calculation involves converting grams of water to moles using the molar mass of water (18.02 g/mol). The result of the calculation yields -4.14 kJ, indicating that energy is released during the freezing process. However, the correct interpretation of the question requires reporting the heat emitted as a positive value, thus the final answer is 4.14 kJ.

PREREQUISITES
  • Understanding of heat of fusion in thermodynamics
  • Knowledge of molar mass calculations
  • Familiarity with exothermic and endothermic processes
  • Basic algebra for unit conversions
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  • Study the concept of heat of fusion in detail
  • Learn about exothermic and endothermic reactions
  • Explore molar mass calculations and their applications
  • Review thermodynamic principles related to phase changes
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Students studying chemistry, particularly those focusing on thermodynamics and phase changes, as well as educators looking for clear examples of heat calculations in physical chemistry.

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Homework Statement


Calculate the amount of heat emitted when 12.4 g of water freezes to solid air.

Homework Equations


heat of fusion = 6.02 KJ
1 mol H2O = 18.02 g H2O

The Attempt at a Solution


12.4 g H2O x 1 mol H2O/ 18.02 g H2O x (-6.02 KJ) / 1 mol H2O = - 4.14 kJ

I am unsure whether the answer is positive or negative.
The answer in the book is positive 4.14 kJ, but freezing is exothermic ( releasing energy).
 
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You have to pay attention to the language. The question asks for "the amount of heat emitted", which will be minus the heat change of the water, that latter being what you calculated.
 
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