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Ch.6 - Thermochemistry
All textbooksTro 4th EditionCh.6 - ThermochemistryProblem 118
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Chapter 6, Problem 118

A pure gold ring and a pure silver ring have a total mass of 14.9 g. The two rings are heated to 62.0 °C and dropped into 15.0 mL of water at 23.5 °C. When equilibrium is reached, the temperature of the water is 25.0 °C. What is the mass of each ring? (Assume a density of 0.998 g/mL for water.)

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1
Identify the specific heat capacities of gold and silver, which are approximately 0.129 J/g°C and 0.235 J/g°C, respectively.
Use the formula for heat transfer: \( q = mc\Delta T \), 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.
Calculate the heat gained by the water using its mass (15.0 mL \( \times \) 0.998 g/mL) and its temperature change (25.0 °C - 23.5 °C).
Set up the equation for heat lost by the rings: \( q_{gold} + q_{silver} = -q_{water} \), where the negative sign indicates that the rings lose heat while the water gains it.
Use the total mass of the rings (14.9 g) and solve the system of equations to find the individual masses of the gold and silver rings.
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Textbook Question

A gaseous fuel mixture contains 25.3% methane (CH4), 38.2% ethane (C2H6), and the rest propane (C3H8) by volume. When the fuel mixture contained in a 1.55 L tank, stored at 755 mmHg and 298 K, undergoes complete combustion, how much heat is emitted? (Assume that the water produced by the combustion is in the gaseous state.)

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Textbook Question

A gaseous fuel mixture stored at 745 mmHg and 298 K contains only methane (CH4) and propane (C3H8). When 11.7 L of this fuel mixture is burned, it produces 769 kJ of heat. What is the mole fraction of methane in the mixture? (Assume that the water produced by the combustion is in the gaseous state.)

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Open Question
A copper cube with an edge measuring 1.55 cm and an aluminum cube with an edge measuring 1.62 cm are both heated to 55.0 °C and submerged in 100.0 mL of water at 22.2 °C. What is the final temperature of the water when equilibrium is reached? (Assume a density of 0.998 g/mL for water.)