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Ch.9 - Thermochemistry: Chemical Energy
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoMcMurry 8th EditionCh.9 - Thermochemistry: Chemical EnergyProblema 7
Capitolo 9, Problema 7

How much heat is required to raise a 50.0 g piece of iron from 25 °C to its melting point of 1538 °C? The specific heat capacity for iron is 0.451 J/g•°C. (a) 34.1 kJ (b) 168 kJ (c) 12.1 kJ (d) 6.78 kJ

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Identify the given values: mass of iron (m) = 50.0 g, initial temperature (T_initial) = 25 °C, final temperature (T_final) = 1538 °C, and specific heat capacity of iron (c) = 0.451 J/g•°C.
Understand the formula for heat transfer, which is Q = m * c * ΔT, where Q is the heat required, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.
Calculate the change in temperature (ΔT) by subtracting the initial temperature from the final temperature: ΔT = T_final - T_initial.
Substitute the values into the heat transfer formula: Q = 50.0 g * 0.451 J/g•°C * (1538 °C - 25 °C).
Convert the result from joules to kilojoules by dividing by 1000, as 1 kJ = 1000 J.

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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 a material-specific property that indicates how much energy is needed to change the temperature of a substance, which is crucial for calculating heat transfer in thermal processes.
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Heat Capacity

Heat Transfer Calculation

The heat transfer (q) required to change the temperature of a substance can be calculated using the formula q = m × c × ΔT, where m is the mass, c is the specific heat capacity, and ΔT is the change in temperature. This formula allows us to quantify the energy needed for temperature changes in various materials.
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Calculations with Heating and Cooling Curves

Phase Change and Melting Point

The melting point is the temperature at which a solid becomes a liquid. In this context, understanding the melting point of iron (1538 °C) is essential, as it indicates the temperature to which the iron must be heated. The energy required to reach this temperature from an initial state is calculated using the specific heat capacity.
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Boiling Point and Melting Point
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