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Ch.9 - Thermochemistry: Chemical Energy
Chapter 9, Problem 78

Sodium metal is sometimes used as a cooling agent in heat-exchange units because of its releatively high molar heat capacity fo 28.2 J/(mol·°C). What is the specific heat and molar heat capacity of sodium in J/g·°C?

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1. The molar heat capacity is given as 28.2 J/(mol·°C). This is the amount of heat required to raise the temperature of one mole of sodium by one degree Celsius.
2. The specific heat capacity is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. To find the specific heat capacity, we need to convert the molar heat capacity to a per gram basis.
3. To do this, we need to know the molar mass of sodium. The molar mass of sodium (Na) is approximately 23 g/mol.
4. We can then divide the molar heat capacity by the molar mass to find the specific heat capacity. The formula to use is: Specific heat capacity = Molar heat capacity / Molar mass.
5. Substitute the given values into the formula to find the specific heat capacity of sodium in J/g·°C.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molar Heat Capacity

Molar heat capacity is the amount of heat required to raise the temperature of one mole of a substance by one degree Celsius. It is typically expressed in units of J/(mol·°C). This property is crucial for understanding how substances absorb and transfer heat, which is essential in applications like heat-exchange units.
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Specific Heat Capacity

Specific heat capacity is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. It is expressed in J/(g·°C). The specific heat capacity allows for comparisons between different materials and is vital for calculating temperature changes in chemical reactions and physical processes.
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Unit Conversion

Unit conversion is the process of converting a quantity expressed in one set of units to another set of units. In this context, converting molar heat capacity (J/(mol·°C)) to specific heat capacity (J/(g·°C)) involves using the molar mass of sodium to relate the two measurements. Understanding unit conversion is essential for accurately interpreting and applying thermodynamic properties.
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