Physics Chapter 7 Flashcards

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Questions and Answers

If ΔE is positive, energy can be written as a product in the equation for the reaction.

True

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?

−5.91 × 10^3 kJ/mol

What is ΔE for the combustion of a 0.900-g sample of toluene, C7H8?

−3900 kJ/mol Signup and view all the answers

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?

4.6 × 10^4 J Signup and view all the answers

What work is done in the conversion of 1.00 mole of Ni to Ni(CO)4 at 75°C?

8.68 × 10^3 J Signup and view all the answers

What is ΔE for the conversion of 2.00 moles of NO2 to N2O4 at 125°C?

3,300 J Signup and view all the answers

Which statement is false regarding thermodynamic processes?

A bomb calorimeter measures ΔH directly. Signup and view all the answers

Which one of the following statements is false?

In the relationship ΔE = q + w, as applied to a typical chemical reaction, w is usually much larger than q. Signup and view all the answers

Which of the following statements regarding spontaneous changes is false?

All exothermic reactions are spontaneous. Signup and view all the answers

What is the change in entropy of the reaction N2(g) + 3H2(g) → 2NH3(g)?

−198.7 J/K Signup and view all the answers

Which of the following statements about free energy is false?

ΔS must be positive for a process to be spontaneous. Signup and view all the answers

Which statement is incorrect?

A process that absorbs energy from its surroundings is called exothermic. Signup and view all the answers

Which of the following statements about the first law of thermodynamics and energy is false?

Kinetic energy = 1/2 mv. Signup and view all the answers

Which of the following statements is a correct interpretation of the First Law of Thermodynamics?

All of these are correct. Signup and view all the answers

Which one of the following thermodynamic quantities is not a state function?

Work Signup and view all the answers

Which term is not correctly matched?

State function / Property dependent on how the process takes place Signup and view all the answers

The enthalpy change, ΔH, of a process is defined as:

The quantity of heat transferred in or out of a system as it undergoes a change at constant pressure. Signup and view all the answers

Which statement regarding enthalpy change is incorrect?

The absolute enthalpy of a system can be experimentally measured. Signup and view all the answers

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?

223 J Signup and view all the answers

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.

55.34 J/°C Signup and view all the answers

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.

44.8 kJ/mol Signup and view all the answers

How much heat is absorbed in the complete reaction of 3.00 grams of SiO2 with excess carbon?

31.2 kJ Signup and view all the answers

How much heat is released when 75 g of octane is burned completely?

3600 kJ Signup and view all the answers

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?

−55 kJ/mol Signup and view all the answers

How much heat is released when the burning of 80.3 g of SiH4 at constant pressure gives off heat?

−1520 kJ/mol rxn Signup and view all the answers

What is the ΔH of the reaction for the roasting of 48.7 g of ZnS at constant pressure that gives off heat?

−881 kJ/mol rxn Signup and view all the answers

Which of the following statements is incorrect regarding the thermochemical standard state?

A superscript zero, such as ΔH0, indicates a specified temperature of 0°C. Signup and view all the answers

Which of the following substances is not in its standard state?

O3, (g) Signup and view all the answers

For which of the following substances does ΔHf^0 = 0?

Na(s) Signup and view all the answers

Which of the following substances is not correctly matched with its molar heat of formation?

Br2(g) / = 0 Signup and view all the answers

Calculate the amount of heat released in the complete combustion of 8.17 grams of Al to form Al2O3(s).

254 kJ Signup and view all the answers

How much heat energy is liberated when 11.0 grams of manganese is converted to Mn2O3 at standard state conditions?

96.2 kJ Signup and view all the answers

When 32.1 g of H2 reacts with excess silicon to form SiH4(g) at standard conditions, how much heat is absorbed?

33.7 kJ/mol Signup and view all the answers

Which of the following is not a formation reaction?

H2O + SO3 → H2SO4 Signup and view all the answers

From the data provided, calculate ΔH0 at 25°C for this reaction: 4HCl(g) + O2(g) → 2Cl2(g) + 2H2O(g).

−114 kJ Signup and view all the answers

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).

−55.3 kJ Signup and view all the answers

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.

−110.5 kJ Signup and view all the answers

Given the standard heats of formation for the following compounds, calculate for the reaction: CH4(g) + H2O(g) → CH3OH + H2(g).

+79 kJ Signup and view all the answers

Calculate ΔH0 at 25°C for the reaction 2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g).

−879.0 kJ Signup and view all the answers

Calculate ΔH0 for the following reaction at 25.0°C: Fe3O4(s) + CO(g) → 3FeO(s) + CO2(g).

19 kJ Signup and view all the answers

Calculate the standard enthalpy change for the reaction C(graphite) + 4HNO3 → CO2(g) + 4NO2(g) + 2H2O.

−135.9 kJ Signup and view all the answers

Calculate the standard enthalpy change for the reaction 12NH3(g) + 21O2(g) → 8HNO3 + 4NO(g) + 14H2O(g).

−3,540 kJ Signup and view all the answers

Evaluate ΔH0 for the reaction SiO2(s) + 4HF(aq) → SiF4(g) + 2H2O.

7.5 kJ Signup and view all the answers

Use the provided data to calculate for benzene, C6H6, at 25°C and 1 atm.

49.1 kJ/mol Signup and view all the answers

Given the following data, calculate for HCN(g) at 25°C: 2NH3(g) + 3O2(g) + 2CH4(g) → 2HCN(g) + 6H2O.

+135 kJ/mol Signup and view all the answers

Given that ΔH0 for the oxidation of sucrose, C12H22O11(s), is −5648 kJ per mole at 25°C, evaluate for sucrose.

−2218 kJ/mol Signup and view all the answers

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).

−110.5 kJ/mol Signup and view all the answers

How much heat is evolved in the formation of 35.0 grams of Fe2O3(s) at 25°C and 1.00 atm pressure?

180.7 kJ Signup and view all the answers

How much heat is released when 6.38 grams of Ag(s) reacts according to the equation at standard state conditions?

8.80 kJ Signup and view all the answers

How much heat is released or absorbed during the reaction of 10.0 grams of SiO2 with excess hydrofluoric acid?

1.25 kJ absorbed Signup and view all the answers

How much heat would be released or absorbed if 575 g of H2 is produced from the reaction?

1.97 × 10^4 kJ Signup and view all the answers

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?

668 kJ Signup and view all the answers

Calculate the standard heat of vaporization for tin(IV) chloride, SnCl4, in kJ per mole.

39.8 Signup and view all the answers

Which of the following techniques cannot be used to calculate ΔHrxn?

Using melting points of reactants and products Signup and view all the answers

The heat of reaction of one of the following reactions is the average bond energy for the N-H bond in NH3. Which one?

1/3NH3(g) → 1/3N(g) + H(g) Signup and view all the answers

Evaluate ΔH0 for the following reaction from the given bond energies: 2HBr(g) → H2(g) + Br2(g).

+103 kJ Signup and view all the answers

Estimate the enthalpy change for the reaction given the average bond energies below: CH4(g) + 2Cl2(g) → CH2Cl2(g) + 2HCl(g).

−232 kJ/mol Signup and view all the answers

Estimate the heat of reaction at 298 K for the reaction given: Br2(g) + 3F2(g) → 2BrF3(g).

−836 kJ Signup and view all the answers

Calculate the average N−H bond energy in NH3(g).

−390.9 kJ Signup and view all the answers

Calculate the average S−F bond energy in SF6.

327.0 kJ Signup and view all the answers

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.

431 kJ Signup and view all the answers

Calculate the average bond energy in kJ per mol of bonds for the C−H bond.

415.9 kJ/mol Signup and view all the answers

The heat of gaseous acetylene, H−C≡C−H, is 227 kJ/mol. What is the C≡C bond energy?

817 kJ/mol Signup and view all the answers

Which of the following statements about internal energy, E, is false?

ΔE is positive in exothermic reactions. Signup and view all the answers

Consider the following reaction at constant pressure. Which response is true? N2(g) + O2(g) → 2NO(g)

No work is done as the reaction occurs. Signup and view all the answers

Which statement concerning sign conventions for ΔE = q + w is false?

For heat absorbed by the system, q is positive. Signup and view all the answers

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

Each reaction can liberate or absorb significant amounts of energy, influencing reaction drive and practicality.
Understanding these principles lays the groundwork for further studies in chemistry and related fields.### Thermodynamic Changes and Reactions
Formation of Nickel Carbonyl:
- Reaction: Ni(s) + 4CO(g) → Ni(CO)4(g)
- ΔH value: +8.68 × 10^3 J
NO2 to N2O4 Reaction:
- Reaction: 2NO2(g) → N2O4(g)
- Work done calculated: +3,300 J at 125°C
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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Test your knowledge with these flashcards focused on concepts from Chapter 7 of Physics. Explore energy types, laws of thermodynamics, and other related definitions. Determine which statements about energy and processes are correct or incorrect.