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Questions and Answers
If ΔE is positive, energy can be written as a product in the equation for the reaction.
If ΔE is positive, energy can be written as a product in the equation for the reaction.
True (A)
Which response is false regarding the reaction CH4(g) + 2O2(g) → CO2(g) + 2H2O?
Which response is false regarding the reaction CH4(g) + 2O2(g) → CO2(g) + 2H2O?
- Work is done by the surroundings on the system.
- The volume must increase at constant pressure. (correct)
- Heat is released by the system.
- All of these statements are true.
- Work is positive.
What is ΔE for the combustion of a 1.00-g sample of hexane, C6H14?
What is ΔE for the combustion of a 1.00-g sample of hexane, C6H14?
−5.91 × 10^3 kJ/mol
What is ΔE for the combustion of a 0.900-g sample of toluene, C7H8?
What is ΔE for the combustion of a 0.900-g sample of toluene, C7H8?
What is the amount of work done when a system is compressed from 50.0 L to 5.0 L at a constant pressure of 10.0 atm?
What is the amount of work done when a system is compressed from 50.0 L to 5.0 L at a constant pressure of 10.0 atm?
What work is done in the conversion of 1.00 mole of Ni to Ni(CO)4 at 75°C?
What work is done in the conversion of 1.00 mole of Ni to Ni(CO)4 at 75°C?
What is ΔE for the conversion of 2.00 moles of NO2 to N2O4 at 125°C?
What is ΔE for the conversion of 2.00 moles of NO2 to N2O4 at 125°C?
Which statement is false regarding thermodynamic processes?
Which statement is false regarding thermodynamic processes?
Which one of the following statements is false?
Which one of the following statements is false?
Which of the following statements regarding spontaneous changes is false?
Which of the following statements regarding spontaneous changes is false?
What is the change in entropy of the reaction N2(g) + 3H2(g) → 2NH3(g)?
What is the change in entropy of the reaction N2(g) + 3H2(g) → 2NH3(g)?
Which of the following statements about free energy is false?
Which of the following statements about free energy is false?
Which statement is incorrect?
Which statement is incorrect?
Which of the following statements about the first law of thermodynamics and energy is false?
Which of the following statements about the first law of thermodynamics and energy is false?
Which of the following statements is a correct interpretation of the First Law of Thermodynamics?
Which of the following statements is a correct interpretation of the First Law of Thermodynamics?
Which one of the following thermodynamic quantities is not a state function?
Which one of the following thermodynamic quantities is not a state function?
Which term is not correctly matched?
Which term is not correctly matched?
The enthalpy change, ΔH, of a process is defined as:
The enthalpy change, ΔH, of a process is defined as:
Which statement regarding enthalpy change is incorrect?
Which statement regarding enthalpy change is incorrect?
How much heat was absorbed by the calorimeter in an exothermic reaction that liberates 7.58 kJ of heat in a coffee cup calorimeter containing 157 grams of solution?
How much heat was absorbed by the calorimeter in an exothermic reaction that liberates 7.58 kJ of heat in a coffee cup calorimeter containing 157 grams of solution?
Calculate the heat capacity of the calorimeter (in J/°C) if 4.168 kJ of heat is added to a calorimeter containing 75.40 g of water, which increases in temperature from 24.58°C to 35.82°C.
Calculate the heat capacity of the calorimeter (in J/°C) if 4.168 kJ of heat is added to a calorimeter containing 75.40 g of water, which increases in temperature from 24.58°C to 35.82°C.
Calculate the molar heat of neutralization for the reaction between 50.0 mL solution of 1.2 M HCl and 50.0 mL of 1.3 M NaOH resulting in a final temperature of 29.8°C.
Calculate the molar heat of neutralization for the reaction between 50.0 mL solution of 1.2 M HCl and 50.0 mL of 1.3 M NaOH resulting in a final temperature of 29.8°C.
How much heat is absorbed in the complete reaction of 3.00 grams of SiO2 with excess carbon?
How much heat is absorbed in the complete reaction of 3.00 grams of SiO2 with excess carbon?
How much heat is released when 75 g of octane is burned completely?
How much heat is released when 75 g of octane is burned completely?
What is the molar heat of neutralization, ΔH, for the reaction of 5.5 grams of HCl with excess Ba(OH)2 that releases 8300 J of heat?
What is the molar heat of neutralization, ΔH, for the reaction of 5.5 grams of HCl with excess Ba(OH)2 that releases 8300 J of heat?
How much heat is released when the burning of 80.3 g of SiH4 at constant pressure gives off heat?
How much heat is released when the burning of 80.3 g of SiH4 at constant pressure gives off heat?
What is the ΔH of the reaction for the roasting of 48.7 g of ZnS at constant pressure that gives off heat?
What is the ΔH of the reaction for the roasting of 48.7 g of ZnS at constant pressure that gives off heat?
Which of the following statements is incorrect regarding the thermochemical standard state?
Which of the following statements is incorrect regarding the thermochemical standard state?
Which of the following substances is not in its standard state?
Which of the following substances is not in its standard state?
For which of the following substances does ΔHf^0 = 0?
For which of the following substances does ΔHf^0 = 0?
Which of the following substances is not correctly matched with its molar heat of formation?
Which of the following substances is not correctly matched with its molar heat of formation?
Calculate the amount of heat released in the complete combustion of 8.17 grams of Al to form Al2O3(s).
Calculate the amount of heat released in the complete combustion of 8.17 grams of Al to form Al2O3(s).
How much heat energy is liberated when 11.0 grams of manganese is converted to Mn2O3 at standard state conditions?
How much heat energy is liberated when 11.0 grams of manganese is converted to Mn2O3 at standard state conditions?
When 32.1 g of H2 reacts with excess silicon to form SiH4(g) at standard conditions, how much heat is absorbed?
When 32.1 g of H2 reacts with excess silicon to form SiH4(g) at standard conditions, how much heat is absorbed?
Which of the following is not a formation reaction?
Which of the following is not a formation reaction?
From the data provided, calculate ΔH0 at 25°C for this reaction: 4HCl(g) + O2(g) → 2Cl2(g) + 2H2O(g).
From the data provided, calculate ΔH0 at 25°C for this reaction: 4HCl(g) + O2(g) → 2Cl2(g) + 2H2O(g).
Given the following at 25°C: 1/2N2(g) + O2(g) → NO2(g) ΔH0 = 33.2 kJ. Calculate the ΔH0 for 2NO2(g) → N2O4(g).
Given the following at 25°C: 1/2N2(g) + O2(g) → NO2(g) ΔH0 = 33.2 kJ. Calculate the ΔH0 for 2NO2(g) → N2O4(g).
Given the enthalpy changes for the following reactions, calculate for CO(g): C (graphite) + O2(g) → CO2(g) = −393.5 kJ, CO(g) + 1/2O2 → CO2(g) ΔH0 = −283.0 kJ.
Given the enthalpy changes for the following reactions, calculate for CO(g): C (graphite) + O2(g) → CO2(g) = −393.5 kJ, CO(g) + 1/2O2 → CO2(g) ΔH0 = −283.0 kJ.
Given the standard heats of formation for the following compounds, calculate for the reaction: CH4(g) + H2O(g) → CH3OH + H2(g).
Given the standard heats of formation for the following compounds, calculate for the reaction: CH4(g) + H2O(g) → CH3OH + H2(g).
Calculate ΔH0 at 25°C for the reaction 2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g).
Calculate ΔH0 at 25°C for the reaction 2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g).
Calculate ΔH0 for the following reaction at 25.0°C: Fe3O4(s) + CO(g) → 3FeO(s) + CO2(g).
Calculate ΔH0 for the following reaction at 25.0°C: Fe3O4(s) + CO(g) → 3FeO(s) + CO2(g).
Calculate the standard enthalpy change for the reaction C(graphite) + 4HNO3 → CO2(g) + 4NO2(g) + 2H2O.
Calculate the standard enthalpy change for the reaction C(graphite) + 4HNO3 → CO2(g) + 4NO2(g) + 2H2O.
Calculate the standard enthalpy change for the reaction 12NH3(g) + 21O2(g) → 8HNO3 + 4NO(g) + 14H2O(g).
Calculate the standard enthalpy change for the reaction 12NH3(g) + 21O2(g) → 8HNO3 + 4NO(g) + 14H2O(g).
Evaluate ΔH0 for the reaction SiO2(s) + 4HF(aq) → SiF4(g) + 2H2O.
Evaluate ΔH0 for the reaction SiO2(s) + 4HF(aq) → SiF4(g) + 2H2O.
Use the provided data to calculate for benzene, C6H6, at 25°C and 1 atm.
Use the provided data to calculate for benzene, C6H6, at 25°C and 1 atm.
Given the following data, calculate for HCN(g) at 25°C: 2NH3(g) + 3O2(g) + 2CH4(g) → 2HCN(g) + 6H2O.
Given the following data, calculate for HCN(g) at 25°C: 2NH3(g) + 3O2(g) + 2CH4(g) → 2HCN(g) + 6H2O.
Given that ΔH0 for the oxidation of sucrose, C12H22O11(s), is −5648 kJ per mole at 25°C, evaluate for sucrose.
Given that ΔH0 for the oxidation of sucrose, C12H22O11(s), is −5648 kJ per mole at 25°C, evaluate for sucrose.
At 25°C for CO(g), given that ΔH0 for the reaction 2CH4(g) + O2(g) + 4Cl2(g) → 8HCl(g) + 2CO(g) is −809.9 kJ, calculate for CO(g).
At 25°C for CO(g), given that ΔH0 for the reaction 2CH4(g) + O2(g) + 4Cl2(g) → 8HCl(g) + 2CO(g) is −809.9 kJ, calculate for CO(g).
How much heat is evolved in the formation of 35.0 grams of Fe2O3(s) at 25°C and 1.00 atm pressure?
How much heat is evolved in the formation of 35.0 grams of Fe2O3(s) at 25°C and 1.00 atm pressure?
How much heat is released when 6.38 grams of Ag(s) reacts according to the equation at standard state conditions?
How much heat is released when 6.38 grams of Ag(s) reacts according to the equation at standard state conditions?
How much heat is released or absorbed during the reaction of 10.0 grams of SiO2 with excess hydrofluoric acid?
How much heat is released or absorbed during the reaction of 10.0 grams of SiO2 with excess hydrofluoric acid?
How much heat would be released or absorbed if 575 g of H2 is produced from the reaction?
How much heat would be released or absorbed if 575 g of H2 is produced from the reaction?
How much heat would be released if 12.0 g of methane, CH4, was completely burned in oxygen to form carbon dioxide and water at standard state conditions?
How much heat would be released if 12.0 g of methane, CH4, was completely burned in oxygen to form carbon dioxide and water at standard state conditions?
Calculate the standard heat of vaporization for tin(IV) chloride, SnCl4, in kJ per mole.
Calculate the standard heat of vaporization for tin(IV) chloride, SnCl4, in kJ per mole.
Which of the following techniques cannot be used to calculate ΔHrxn?
Which of the following techniques cannot be used to calculate ΔHrxn?
The heat of reaction of one of the following reactions is the average bond energy for the N-H bond in NH3. Which one?
The heat of reaction of one of the following reactions is the average bond energy for the N-H bond in NH3. Which one?
Evaluate ΔH0 for the following reaction from the given bond energies: 2HBr(g) → H2(g) + Br2(g).
Evaluate ΔH0 for the following reaction from the given bond energies: 2HBr(g) → H2(g) + Br2(g).
Estimate the enthalpy change for the reaction given the average bond energies below: CH4(g) + 2Cl2(g) → CH2Cl2(g) + 2HCl(g).
Estimate the enthalpy change for the reaction given the average bond energies below: CH4(g) + 2Cl2(g) → CH2Cl2(g) + 2HCl(g).
Estimate the heat of reaction at 298 K for the reaction given: Br2(g) + 3F2(g) → 2BrF3(g).
Estimate the heat of reaction at 298 K for the reaction given: Br2(g) + 3F2(g) → 2BrF3(g).
Calculate the average N−H bond energy in NH3(g).
Calculate the average N−H bond energy in NH3(g).
Calculate the average S−F bond energy in SF6.
Calculate the average S−F bond energy in SF6.
Given: H−H bond energy = 435 kJ, Cl−Cl bond energy = 243 kJ, and the standard heat of formation of HCl(g) is −92 kJ/mol, calculate the H−Cl bond energy.
Given: H−H bond energy = 435 kJ, Cl−Cl bond energy = 243 kJ, and the standard heat of formation of HCl(g) is −92 kJ/mol, calculate the H−Cl bond energy.
Calculate the average bond energy in kJ per mol of bonds for the C−H bond.
Calculate the average bond energy in kJ per mol of bonds for the C−H bond.
The heat of gaseous acetylene, H−C≡C−H, is 227 kJ/mol. What is the C≡C bond energy?
The heat of gaseous acetylene, H−C≡C−H, is 227 kJ/mol. What is the C≡C bond energy?
Which of the following statements about internal energy, E, is false?
Which of the following statements about internal energy, E, is false?
Consider the following reaction at constant pressure. Which response is true? N2(g) + O2(g) → 2NO(g)
Consider the following reaction at constant pressure. Which response is true? N2(g) + O2(g) → 2NO(g)
Which statement concerning sign conventions for ΔE = q + w is false?
Which statement concerning sign conventions for ΔE = q + w is false?
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Study Notes
Thermodynamics and Energy
- Energy is defined as the capacity to perform work or transfer heat.
- Kinetic energy refers to the energy associated with motion, while potential energy is linked to an object’s position or composition.
- Processes absorbing energy from surroundings are termed endothermic, while those releasing energy are exothermic.
- The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed.
Enthalpy (ΔH)
- Enthalpy change (ΔH) quantifies heat transferred during a process at constant pressure.
- Enthalpy is a state function, meaning its value depends only on the current state, not how it arrived there.
- The specific heat capacity of a solution can be used to calculate heat absorbed or released based on temperature changes.
Calorimetry
- When substances in a calorimeter react, the heat absorbed or released can be measured using changes in temperature and the specific heat formula.
- The heat capacity of a calorimeter helps in determining the total heat exchange during a reaction.
Heat of Neutralization
- The molar heat of neutralization refers to the heat released when an acid reacts with a base.
- Typical values are calculated using the amount of heat exchanged and the stoichiometry of the reaction.
Standard State and Formation Reactions
- Standard state refers to a substance's most stable form at one atmosphere and specified temperature (usually 298 K).
- The heats of formation (ΔHf) relate to the energy changes when one mole of a compound forms from its elements in their standard states.
Bond Energies
- Bond energy is a measure of the strength of the bonds in a compound; breaking bonds requires energy, while forming bonds releases energy.
- Overall reaction enthalpies can be calculated using average bond energies.
Specific Calculations
- Calculating ΔH for reactions involves using enthalpies of formation or measuring heat changes through calorimetry.
- Average bond energy calculations can estimate the strength of various bonds within a molecule.
Work in Thermodynamics
- Work can be done on or by a system, generally related to volume changes under pressure.
- The work done during thermal processes can be quantified through formulas linking pressure, volume, and changes therein.
Application of Thermodynamic Principles
- Careful application of thermodynamic laws enables the prediction of energy changes and the feasibility of chemical reactions, often vital in industrial and laboratory contexts.
Remember
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Each reaction can liberate or absorb significant amounts of energy, influencing reaction drive and practicality.
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Understanding these principles lays the groundwork for further studies in chemistry and related fields.### Thermodynamic Changes and Reactions
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Formation of Nickel Carbonyl:
- Reaction: Ni(s) + 4CO(g) → Ni(CO)4(g)
- ΔH value: +8.68 × 10^3 J
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NO2 to N2O4 Reaction:
- Reaction: 2NO2(g) → N2O4(g)
- Work done calculated: +3,300 J at 125°C
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False Statements about Energy:
- Bomb calorimeters do not measure ΔH directly.
- In a typical chemical reaction, work done (w) is not usually larger than heat (q).
- For constant pressure processes, work is zero if gaseous moles do not change.
Changes in Gibbs Free Energy (ΔG)
- Standard Energy Changes:
- For H2(g) + O2(g) → H2O(g): ΔE per mole = -240 kJ
- For SiO2(s) + 4HF(aq) → SiF4(g) + 2H2O: ΔE0 = -5.02 kJ/mol
- For reaction of NH3 and O2: ΔE0 = -3,503 kJ/mol
Spontaneity and Entropy
- Spontaneous Reactions:
- Spontaneity is favored by heat release and increased dispersal of matter.
- All exothermic reactions are not necessarily spontaneous.
- Entropy Changes:
- Positive ΔS indicates increased dispersal of matter.
- Process involving changes like rain forming leads to negative ΔS.
Key Concepts in Thermodynamics
- Third Law of Thermodynamics:
- Absolute entropy (S) is zero only at 0 K; it is positive at T > 0 K.
- Heat and Work:
- ΔH = 0 and ΔE = 0 at the melting point in phase changes.
- Free energy change (ΔG) can be calculated using heat and entropy changes.
Chemical Disequilibrium
- Endothermic and Exothermic Processes:
- Reaction entropy can be negative even with exothermic processes.
- Gibbs Free Energy changes are essential in determining thermodynamic favorability.
Reactions and Calculations
- Gibbs Free Energy Calculation:
- ΔG0 for reactions like P4O10 + 6H2O → 4H3PO4 = -363.7 kJ.
- ΔG can be influenced by both enthalpy (ΔH) and entropy (ΔS).
Entropy of Solutions
- Absolute Entropy:
- 1 M NaCl at 50°C possesses the highest absolute entropy among given states.
Conclusion
- Energy changes, entropy, and thermodynamic laws interact closely throughout chemical processes and reactions. The ability to calculate Gibbs Free Energy changes and recognize spontaneous reactions is pivotal in chemistry.
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