Domanda del libro di testo
What is the difference between the internal energy change ∆E and the enthalpy change ∆H? Which of the two is mea- sured at constant pressure and which at constant volume?
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Ch.9 - Thermochemistry: Chemical Energy
McMurry8th EditionChemistryISBN: 9781292336145
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TOC.tableOfContents
- Ch.1 - Chemical Tools: Experimentation & Measurement170
- Ch.2 - Atoms, Molecules & Ions160
- Ch.3 - Mass Relationships in Chemical Reactions169
- Ch.4 - Reactions in Aqueous Solution199
- Ch.5 - Periodicity & Electronic Structure of Atoms102
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory92
- Ch.7 - Covalent Bonding and Electron-Dot Structures61
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure59
- Ch.9 - Thermochemistry: Chemical Energy122
- Ch.10 - Gases: Their Properties & Behavior155
- Ch.11 - Liquids & Phase Changes54
- Ch.12 - Solids and Solid-State Materials73
- Ch.13 - Solutions & Their Properties120
- Ch.14 - Chemical Kinetics98
- Ch.15 - Chemical Equilibrium125
- Ch.16 - Aqueous Equilibria: Acids & Bases110
- Ch.17 - Applications of Aqueous Equilibria147
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium86
- Ch.19 - Electrochemistry154
- Ch.20 - Nuclear Chemistry96
- Ch.21 - Transition Elements and Coordination Chemistry156
- Ch.22 - The Main Group Elements187
- Ch.23 - Organic and Biological Chemistry51
Capitolo 9, Problema 56
When a sample of a hydrocarbon fuel is ignited and burned in oxygen, the internal energy decreases by 7.20 kJ. If 5670 J of heat were transferred to the surroundings, what is the sign and magnitude of work? If the reaction took place in an environ- ment with a pressure of 1 atm, what was the volume change?
Guida verificata passo dopo passo1
First, we need to understand that the internal energy change of a system (ΔU) is given by the equation ΔU = q + w, where q is the heat transferred and w is the work done. In this case, we know that ΔU = -7.20 kJ and q = 5670 J. However, we need to convert q to kJ to match the units of ΔU. So, q = 5670 J * (1 kJ / 1000 J) = 5.67 kJ.
Next, we can substitute the values of ΔU and q into the equation to find w. So, -7.20 kJ = 5.67 kJ + w. Solving for w, we get w = -7.20 kJ - 5.67 kJ.
Then, we need to understand that the work done by a gas is given by the equation w = -PΔV, where P is the pressure and ΔV is the volume change. In this case, we know that P = 1 atm, but we need to convert it to the same units as w, which is kJ. So, P = 1 atm * (101.3 J / (atm*L)) * (1 kJ / 1000 J) = 0.1013 kJ/L.
Now, we can substitute the values of w and P into the equation to find ΔV. So, w = -PΔV becomes w / -P = ΔV.
Finally, we can substitute the values of w and P into the equation to find ΔV. So, ΔV = w / -P.
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First Law of Thermodynamics
The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. In the context of a chemical reaction, the change in internal energy of the system is equal to the heat added to the system minus the work done by the system. This principle is crucial for understanding how energy is conserved during chemical reactions.
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01:18
First Law of Thermodynamics
Work in Thermodynamics
In thermodynamics, work is defined as the energy transferred when a force is applied over a distance. For a gas, work can be calculated using the formula W = -PΔV, where P is the pressure and ΔV is the change in volume. Understanding how to calculate work is essential for determining the energy changes in a system during a reaction, especially when gases are involved.
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01:18First Law of Thermodynamics
Enthalpy and Heat Transfer
Enthalpy is a thermodynamic quantity that represents the total heat content of a system. When a reaction occurs at constant pressure, the heat transferred to or from the surroundings can be related to the change in enthalpy. In this scenario, knowing the heat transferred to the surroundings helps in calculating the work done and understanding the overall energy balance of the reaction.
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02:34Enthalpy of Formation
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A reaction inside a cylindrical container with a movable RAN piston causes the volume to change from 12.0 L to 18.0 L while the pressure outside the container remains constant at 0.975 atm. (The volume of a cylinder is V = pr2h, where h is the height; 1 L # atm = 101.325 J.) (b) The diameter of the piston is 17.0 cm. How far does the piston move?
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At a constant pressure of 0.905 atm, a chemical reaction takes place in a cylindrical container with a movable piston having a diameter of 40.0 cm. During the reaction, the height of the piston drops by 65.0 cm. (The volume of a cylinder is V=pr2h,wherehistheheight;1Latm=101.3J.) (a) What is the change in volume in liters during the reaction?
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At a constant pressure of 0.905 atm, a chemical reaction takes place in a cylindrical container with a movable piston having a diameter of 40.0 cm. During the reaction, the height of the piston drops by 65.0 cm. (The volume of a cylinder is V=pr2h,wherehistheheight;1Latm=101.3J.) (b) What is the value in joules of the work w done during the reaction?
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Domanda del libro di testo
Under what circumstances are ΔE and ΔH essentially equal?
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