Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (c) Water freezes into ice in the freezer.
Ch.9 - Thermochemistry: Chemical Energy
Chapter 9, Problem 9
A 25.0 g piece of granite at 100.0°C was added to 100.0 g of water of 25.0°C, and the temperature rose to 28.4°C. What is the specific heat capacity of the granite? (The specific heat capacity for water is 4.18 J/(g•°C).) (LO 9.10) (a) 0.563 J/(g•°C) (b) 1.53 J/(g•°C) (c) 0.992 J/(g•°C) (d) 0.794 J/(g•°C)

1
Calculate the heat gained by the water using the formula: \( q = m \cdot c \cdot \Delta T \), where \( m \) is the mass of the water, \( c \) is the specific heat capacity of water, and \( \Delta T \) is the change in temperature of the water.
Assume that the heat lost by the granite is equal to the heat gained by the water, due to the principle of conservation of energy.
Calculate the change in temperature of the granite, which is the difference between its initial temperature and the final equilibrium temperature.
Use the formula \( q = m \cdot c \cdot \Delta T \) to express the heat lost by the granite, substituting the mass of the granite and its change in temperature.
Solve for the specific heat capacity of the granite, \( c \), by rearranging the formula to \( c = \frac{q}{m \cdot \Delta T} \) using the heat lost by the granite calculated in step 2.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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 property that varies between different substances, influencing how they absorb and transfer heat. In this problem, the specific heat capacity of granite needs to be calculated based on the heat exchange with water.
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Heat Capacity
Heat Transfer
Heat transfer refers to the movement of thermal energy from one object to another due to a temperature difference. In this scenario, heat is transferred from the hot granite to the cooler water until thermal equilibrium is reached. The principle of conservation of energy dictates that the heat lost by the granite equals the heat gained by the water.
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Heat Capacity
Calorimetry
Calorimetry is the science of measuring the heat of chemical reactions or physical changes. In this context, it involves calculating the heat exchanged between the granite and water using their respective masses, specific heat capacities, and temperature changes. The formula used is q = mcΔT, where q is heat, m is mass, c is specific heat capacity, and ΔT is the change in temperature.
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Constant-Volume Calorimetry
Related Practice
Textbook Question
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Textbook Question
Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (d) Rubbing alcohol evaporates from your skin.
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Textbook Question
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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Textbook Question
When 12.5 g of NH4NO3 is dissolved in 150.0 g of water of 25.0 °C in a coffee cup calorimeter, the final temperature of the solution of 19.7 °C. Assume that the specific heat of the solution is the same as that of water, 4.18 J/(g•°C). What is the ΔH per mol of NH4NO3? (LO 9.10) NH4NO3 (s) → NH4+ (aq) + NO3−(aq) ΔH = ? (a) +3.60 kJ (b) +23.0 kJ (c) +21.3 kJ (d) −3.60 kJ
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Textbook Question
Calculate the enthalpy change for the reaction
C(s) + 2 H2(g) → CH4(g) ΔH = ?
Given the enthalpy values for the following reactions
CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) ΔH = −890.4 kJ
C(s) + O2(g) → CO2(g) ΔH = −393.5 kJ
H2(g) + 1/2 O2(g) → H2O (g) ΔH = −285.8 kJ
(a) −1569.7 kJ
(b) +211.1 kJ
(c) −1855.5 kJ
(d) −74.7 kJ
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Textbook Question
A table of standard enthalpies of formation (ΔH°f) gives a value of −467.9 kJ/mol for NaNO3(s). Which reaction has a ΔH° value of −467.9 kJ?
(a) Na+ (aq) + NO3−(aq) → NaNO3(s)
(b) Na(s) + N(g + O3(g) → NaNO3(s)
(c) Na(s) + 1/2 N2(g) + 3/2 O2(g) → NaNO3(s)
(d) 2 Na(s) + N2(g) + 3 O2(g) → 2 NaNO3(s)
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