Near room temperature, the specific heat capacity of benzene is \(1.05 \mathrm{~J} \cdot\left({ }^{\circ} \mathrm{C}\right)^{-1} \mathrm{~g}^{-1}\). Calculate the heat nceded to raise the temperature of \(50.0 \mathrm{~g}\) of benzene from \(25.3^{\circ} \mathrm{C}\) to \(37.2^{\circ} \mathrm{C}\). (b) A \(1.0-\mathrm{kg}\) block of aluminum is supplied with \(490 \mathrm{~kJ}\) of heat. What is the temperature change of the aluminum? The specific heat capacity of aluminum is \(0.90 \mathrm{~J} \cdot\left({ }^{\circ} \mathrm{C}\right)^{-1} \cdot \mathrm{g}^{-1}\).

Short Answer

Expert verified
The heat needed to raise the temperature of 50.0 g of benzene is 622.05 J; the temperature change of the aluminum block is 543.33^{\circ}C.

Step by step solution

01

Calculate the Heat Needed for Benzene

To find the heat (\(Q\)) needed to raise the temperature of benzene, use the formula \(Q = m \times c \times \triangle T\), where \(m\) is the mass of benzene, \(c\) is the specific heat capacity, and \(\triangle T\) is the change in temperature. First, find the change in temperature with \(\triangle T = T_{final} - T_{initial} = 37.2^{\circ}C - 25.3^{\circ}C\).
02

Calculate Temperature Change for Aluminum

To find the temperature change (\(\triangle T\)) for the aluminum block, rearrange the heat equation to \(\triangle T = \frac{Q}{m \times c}\), where \(Q\) is the heat supplied, in this case in kilojoules, so it should first be converted to joules (\(490 \text{kj} = 490,000 \text{j}\)), \(m\) is the mass in grams (\(1000 \text{g}\)), and \(c\) is the specific heat capacity. Then calculate the temperature change using the provided values.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Calorimetry
Calorimetry is a branch of thermodynamics dedicated to the measurement of the amount of heat energy transferred between objects, which is vital in understanding the conservation of energy principle. It involves the use of a calorimeter, an instrument that insulates a system to accurately measure the heat transfer during chemical reactions or physical changes.

For instance, when calculating the heat needed to raise the temperature of benzene in the exercise, calorimetry principles guide us to apply the specific heat capacity along with the mass and temperature change to find the correct amount of energy. This practice is intrinsic to calorimetry, enabling us to quantify the energy changes without loss or gain from the surroundings.

Students should ensure to consider whether the process is isolated from the environment to prevent external factors from influencing the outcome of the calorimetric calculations. Accurate determination hinges on the exactness of the involved measurements and the quality of the calorimeter used.
Energy Transfer in Thermodynamics
In thermodynamics, energy transfer is primarily concerned with how thermal energy moves from one body to another and what it does when it gets there. It's a core concept that illustrates how energy in the form of heat can lead to a change in temperature, phase, or even perform work on another system.

Thermal energy transfer can occur via three primary modes: conduction, convection, and radiation. Within the realm of calorimetry and exercises similar to our textbook problem, we focus on the conduction part — the direct transfer of energy through matter. This transfer is mathematically represented by the equation \(Q = m \times c \times \triangle T\), tying together mass, specific heat capacity, and temperature change.

Understanding this fundamental relationship helps students to predict the outcome of heating or cooling a substance. For instance, when supplying heat to the aluminum block in our exercise, knowing the specific heat capacity allows us to determine how much the temperature will change as a result of the energy transfer.
Temperature Change Calculation
The process of calculating temperature change is fundamental in both theoretical and practical applications of thermodynamics. When a substance absorbs or loses heat, its temperature changes, a concept illustrated in our exercise with benzene and aluminum.

The temperature change \(\Delta T\) can be found using the relation \(\Delta T = T_{final} - T_{initial}\). In the context of the exercise, we use the formula \(Q = m \times c \times \Delta T\) to find the heat energy involved in changing the temperature of a given mass of a substance with known specific heat capacity. For solid and liquid materials like benzene or aluminum, this is often straightforward if we assume no phase change occurs.

Importantly, students should note that specific heat capacity is a property that varies with temperature but can be treated as constant over small temperature ranges, like in our exercise. Remembering to convert energy units when needed and matching them with the mass unit will ensure accurate calculations. The clarity in these step-by-step processes fosters a deeper comprehension of energy dynamics in diverse thermal systems.

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Most popular questions from this chapter

Write the thermochemical equations that give the values of the standard enthalpies of formation for (a) \(\mathrm{KClO}_{3}\) (s), potassium chlorate; (b) \(\mathrm{H}_{2} \mathrm{NCH}_{2} \mathrm{COOH}\) (s), glycine(s); (c) \(\mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{~s})\), alumina.

Write the thermochemical equations that give the values of the standard enthalpies of formation for (a) \(\mathrm{CH}_{2} \mathrm{COOH}\) (I); (b) \(\mathrm{SO}_{2}\) (g); (c) \(\mathrm{CO}_{2}\) (g).

(a) Calculate the work for a system that releases \(346 \mathrm{~kJ}\) of heat in a process for which the decrease in internal energy is \(125 \mathrm{~kJ}\). (b) Is work done on or by the system during this process?

Identify the following systems as open, closed, or isolated: (a) coffec in a very high quality thermos bottle; (b) coolant in a refrigerator coil; (c) a bomb calorimeter in which benzene is bumed.

Use the enthalpies of formation in Appendix \(2 \mathrm{~A}\) to calculate the standard enthalpy of the following reactions: (a) the replacement of deuterium by ordinary hydrogen in heavy water: \(\mathrm{H}_{2}(\mathrm{~g})+\mathrm{D}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{D}_{2}(\mathrm{~g})\) (b) the removal of sulfur from the hydrogen sulfide and sulfur dioxide in natural gas: \(2 \mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})+\mathrm{SO}_{2}(\mathrm{~g}) \rightarrow 3 \mathrm{~S}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})\) (c) the oxidation of ammonia: \(4 \mathrm{NH}_{3}(\mathrm{~g})+5 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 4 \mathrm{NO}(\mathrm{g})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})\)

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