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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970당신이 사용하는 게 아니라요?교과서 변경
5장, 문제 108

A house is designed to have passive solar energy features. Brickwork incorporated into the interior of the house acts as a heat absorber. Each brick weighs approximately 1.8 kg. The specific heat of the brick is 0.85 J/g•K. How many bricks must be incorporated into the interior of the house to provide the same total heat capacity as 1.7⨉103 gal of water?

검증된 단계별 안내
1
Calculate the total mass of water in kilograms, knowing that 1 gallon of water weighs approximately 3.785 kg.
Convert the mass of water from kilograms to grams, since the specific heat is given in J/g•K.
Calculate the total heat capacity of the water using the formula: Heat Capacity = mass (g) × specific heat (J/g•K) × temperature change (ΔT). Since we are comparing capacities, ΔT can be considered as 1 K for simplification.
Calculate the heat capacity of one brick using its mass (1.8 kg converted to grams) and its specific heat (0.85 J/g•K) with ΔT as 1 K.
Divide the total heat capacity of the water by the heat capacity of one brick to find the number of bricks needed to match the heat capacity of the water.

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주요 개념

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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 crucial property that determines how much energy a material can store. In this question, the specific heat of the bricks (0.85 J/g•K) indicates how effectively they can absorb and retain heat compared to water.
추천 영상:

Heat Capacity

Heat capacity is the total amount of heat energy a substance can store, which depends on both its mass and specific heat capacity. It is calculated by multiplying the mass of the substance by its specific heat. In this scenario, we need to equate the heat capacity of the bricks to that of a large volume of water to determine how many bricks are needed.
추천 영상:

Conversion of Units

Conversion of units is essential in chemistry to ensure that measurements are compatible when performing calculations. In this question, the volume of water (1.7×10^3 gallons) must be converted to mass (in grams) to compare it with the mass of the bricks. Understanding how to convert gallons to liters and then to grams using the density of water is necessary for solving the problem.
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Conversion Factors
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교과서 질문

A coffee-cup calorimeter of the type shown in Figure 5.18 contains 150.0 g of water at 25.1°C A 121.0-g block of copper metal is heated to 100.4°C by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g-K The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.1°C (b) Determine the amount of heat gained by the water. The specific heat of water is 4.184 J/1gK.

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교과서 질문

Consider a system consisting of the following apparatus, in which gas is confined in one flask and there is a vacuum in the other flask. The flasks are separated by a valve. Assume that the flasks are perfectly insulated and will not allow the flow of heat into or out of the flasks to the surroundings. When the valve is opened, gas flows from the filled flask to the evacuated one. (a) Is work performed during the expansion of the gas? (b) Why or why not?

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교과서 질문

A system consists of a sample of gas contained in a cylinder-and-piston arrangement. It undergoes the change in state shown in the drawing under two different situations: In Case 1, the cylinder and piston are perfect thermal insulators that do not allow heat to be transferred. In Case 2, the cylinder and piston are made up of a thermal conductor such as a metal, and during the state change, the cylinder gets warmer to the touch. Let 𝑞1,𝑤1, and Δ𝐸1 be the values of q, w, and Δ𝐸 for Case 1, and let 𝑞2,𝑤2, and Δ𝐸2 be the values for Case 2. b. What is the sign of 𝑤1?

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교과서 질문

Potassium superoxide, KO2, is often used in oxygen masks (such as those used by firefighters) because KO2 reacts with CO2 to release molecular oxygen. Experiments indicate that 2 mol of KO2(s) react with each mole of CO2(g). (b) Indicate the oxidation number for each atom involved in the reaction in part (a). What elements are being oxidized and reduced?

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교과서 질문

A coffee-cup calorimeter of the type shown in Figure 5.18 contains 150.0 g of water at 25.1°C A 121.0-g block of copper metal is heated to 100.4°C by putting it in a beaker of boiling water. The specific heat of Cu(s) is 0.385 J/g-K The Cu is added to the calorimeter, and after a time the contents of the cup reach a constant temperature of 30.1°C. (a) Determine the amount of heat, in J, lost by the copper block.

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