How much heat (in J) is released when 0.9 L of water freezes at 0.0°C? The heat of fusion of water (the heat required to freeze it) is -6000 J/mol. The density of water is 1.0 g/ml.
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
![**Calculating Heat Released During Freezing of Water**
**Problem Description:**
How much heat (in J) is released when 0.9 L of water freezes at 0.0°C? The heat of fusion of water (the heat required to freeze it) is -6000 J/mol. The density of water is 1.0 g/mL.
**Solution:**
1. **Convert the volume of water to mass:**
Since the density of water is 1.0 g/mL (which also converts directly to 1.0 g/mL meaning 1 L = 1000 mL), the mass (m) of 0.9 L of water can be calculated as follows:
\[
m = 0.9 \, \text{L} \times 1000 \, \text{mL/L} \times 1.0 \, \text{g/mL} = 900 \, \text{g}
\]
2. **Convert the mass of water to moles:**
The molar mass of water (H₂O) is approximately 18.0 g/mol. Thus, the number of moles (n) of 900 g of water is:
\[
n = \frac{900 \, \text{g}}{18.0 \, \text{g/mol}} = 50 \, \text{mol}
\]
3. **Calculate the heat released:**
The heat of fusion of water is given as -6000 J/mol. Thus, the total heat (Q) released when 50 mol of water freezes is:
\[
Q = 50 \, \text{mol} \times (-6000 \, \text{J/mol}) = -300,000 \, \text{J}
\]
The negative sign indicates that heat is released in the process.
**Conclusion:**
The heat released when 0.9 L of water freezes at 0.0°C is 300,000 J.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F7b0fedb7-adbc-492c-aa14-9f5d12342848%2Fa1ab657f-f1ce-4806-8fc7-a800d8a7c210%2Fui2x98k_processed.jpeg&w=3840&q=75)
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