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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 15th Edition
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Tutti i libri di testoBrown 15th EditionCh.5 - ThermochemistryProblema 53a
Capitolo 5, Problema 53a

The specific heat of ethanol, C2H5OH(l), is 2.44 J•g/K. (a) How many J of heat are needed to raise the temperature of 80.0 g of octane from 10.0 to 25.0 °C?

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Identify the formula for calculating heat: \( q = m \cdot c \cdot \Delta T \), where \( q \) is the heat absorbed or released, \( m \) is the mass, \( c \) is the specific heat capacity, and \( \Delta T \) is the change in temperature.
Note that the problem provides the specific heat of ethanol, but asks about octane. Ensure you have the correct specific heat for octane if needed.
Calculate the change in temperature \( \Delta T \) by subtracting the initial temperature from the final temperature: \( \Delta T = 25.0 \, ^\circ\text{C} - 10.0 \, ^\circ\text{C} \).
Substitute the given values into the formula: \( q = 80.0 \, \text{g} \times c \times \Delta T \).
Solve for \( q \) to find the amount of heat needed.

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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 (or Kelvin). It is a material-specific property that indicates how much energy is needed to change the temperature of a substance, which is crucial for calculations involving heat transfer.
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Heat Capacity

Heat Transfer Equation

The heat transfer equation, often expressed as q = mcΔT, relates the heat (q) absorbed or released by a substance to its mass (m), specific heat capacity (c), and the change in temperature (ΔT). This equation is fundamental for solving problems involving temperature changes in substances, allowing for the calculation of heat energy based on the specific heat and mass.
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Heat Capacity

Temperature Change

Temperature change (ΔT) is the difference between the final and initial temperatures of a substance. It is a critical component in the heat transfer equation, as it directly influences the amount of heat energy required to achieve a desired temperature change. Understanding how to calculate ΔT is essential for accurately determining heat transfer in chemical processes.
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Temperature Conversion Formulas
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Consider the data about gold metal in Exercise 5.24(b). c. What is the molar heat capacity of Au(s)?

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(d) How many kJ of heat are needed to raise the temperature of 10.00 kg of liquid water from 24.6 to 46.2 °C?

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Consider the data about gold metal in Exercise 5.24(b). b. Suppose that the same amount of heat is added to two 10.0-g blocks of metal, both initially at the same temperature. One block is gold metal, and the other is iron metal. Which block will have the greater rise in temperature after addition of the heat?

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The specific heat of ethanol, C2H5OH(l), is 2.44 J•g/K. b. Which will require more heat, increasing the temperature of 1 mol of C2H5OH(𝑙) by a certain amount or increasing the temperature of 1 mol of H2O(𝑙) by the same amount?

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(b) Calculate the energy needed for this temperature change.

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(c) What is the heat capacity of 185 g of liquid water?

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