Exam 2 - Chemistry 1202
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Questions and Answers

What is the significance of using a scientific calculator during the exam?

  • It allows for complex calculations beyond basic arithmetic. (correct)
  • It helps to visualize chemical reactions.
  • It is necessary for creating diagrams.
  • It is required for graphing functions.

    • Which statement about the scantron instructions is correct?

  • Students may leave a question blank if unsure of the answer.
  • Only the answers should be recorded on side one of the scantron. (correct)
  • Personal scratch paper can be used during the exam.
  • Answers must be marked using a pen for clarity.

    • What does the formula ΔGrxn = ΔHrxn − TΔSrxn represent?

  • The relationship between pressure and volume in gases.
  • The calculation of enthalpy change in a reaction.
  • The calculation of free energy change for a chemical reaction. (correct)
  • The relationship between heat and work done during a reaction.

    • What is the appropriate action if a student creates an answer sheet on the back of the exam?

    <p>The answer sheet will not be considered during grading.</p> Signup and view all the answers

    Which reaction is most likely to result in a decrease in the entropy of the system?

    <p>A gas condensing into a liquid.</p> Signup and view all the answers

    What should a student do if they require a formula reference during the exam?

    <p>Refer to the periodic table located at the back of the exam booklet.</p> Signup and view all the answers

    What does the equation K_eq = exp(-ΔG°/RT) signify in chemical thermodynamics?

    <p>The relationship between Gibbs free energy and temperature.</p> Signup and view all the answers

    Which of the following is NOT allowed during the exam according to the guidelines?

    <p>Using personal scratch paper.</p> Signup and view all the answers

    What is the Ksp of BaSO4 at the given temperature?

    <p>1.10 × 10–10</p> Signup and view all the answers

    Calculate the value of ΔGrxn at a temperature of 700 K given ΔHorxn = 114.44 kJ/mol and ΔSorxn = 128.18 J/mol-K.

    <p>140.6 kJ/mol</p> Signup and view all the answers

    Given the partial pressures, what is the ∆G for the reaction P2 (g) + 3 Cl2 (g) ⇋ 2 PCl3 (g) at 298 K?

    <p>–663.3 kJ/mol</p> Signup and view all the answers

    What is the heat of reaction, ΔHorxn, for the combustion of a mole of phenol when the temperature of the calorimeter increases from 23.54°C to 37.86°C?

    <p>1.05 x 10⁴ kJ/mol</p> Signup and view all the answers

    Which of the following salts will be least soluble in water, resulting in the lowest concentration of [Ag+]?

    <p>AgI with Ksp = 8.3 x 10⁻¹⁹</p> Signup and view all the answers

    If the molar mass of phenol is 94.11 g/mol, what is the heat released upon combustion by burning 3 moles in the calorimeter?

    <p>9.15 x 10⁴ kJ/mol</p> Signup and view all the answers

    What is the enthalpy change ΔHorxn for the reaction if ΔGrxn is known to be –200 kJ/mol and ΔSorxn is 50 J/mol-K at 298 K?

    <p>–350 kJ/mol</p> Signup and view all the answers

    What will be the effect on ΔGrxn if the temperature is increased for a reaction that is endothermic?

    <p>ΔGrxn will decrease</p> Signup and view all the answers

    Which compound will NOT have ∆Hof = 0 kJ/mol?

    <p>H2O (l)</p> Signup and view all the answers

    Calculate ΔH in kJ/mol of NaOH when 8.00 g of NaOH is dissolved in 150.0 g of water, raising the temperature from 25.00°C to 85.00°C. The specific heat of water is 4.184 J/g·°C and the molar mass of NaOH is 40.00 g/mol.

    <p>ΔH = 20.4 kJ/mol</p> Signup and view all the answers

    How much work (in kJ) is done when a gas expands from a volume of 20.0 L to 50.0 L against a constant pressure of 3.00 atm?

    <p>–7.82 kJ</p> Signup and view all the answers

    If 10.0 g of CaC2 reacts with water and releases heat at ΔHof of –150.0 kJ/mol, how much heat is released by the reaction?

    <p>–23.1 kJ</p> Signup and view all the answers

    Which process describes a change that is dependent on the path taken?

    <p>The total distance traveled by a car.</p> Signup and view all the answers

    How much heat is needed to raise the temperature of 6.00 kg of aluminum from 200.0°C to 700.0°C? The specific heat of aluminum is 0.90 J/g·°C.

    <p>403.2 kJ</p> Signup and view all the answers

    What is the enthalpy of fusion for mercury (Hg), given that its normal freezing point is –38.9°C?

    <p>4.83 kJ/mol</p> Signup and view all the answers

    Which of the following reactions depicts standard enthalpy of formation values of zero?

    <p>S (s) ⟶ S (s)</p> Signup and view all the answers

    Study Notes

    Exam 2 - Chemistry 1202

    • Exam format: Closed notes, closed book, only a scientific calculator is allowed.
    • Content: Includes questions that require understanding of entropy, enthalpy, Gibbs free energy, calorimetry, and solubility.
    • Useful info:
      • The periodic table is provided.
      • Relevant equations:
        • ΔGrxn = ΔHrxn − TΔSrxn
        • ΔE = q + w
        • ΔS = q / T
        • ΔG = ΔG° + RT(ln Q)
        • K eq = exp(−ΔG° / RT)
        • Cs = q / (m × ΔT)
        • q = −Ccal × ΔT
    • Question 1:
      • Understand which reaction leads to an increase in the entropy of the system.
      • Entropy typically increases if products have more moles of gas than reactants.
    • Question 2:
      • Know that standard enthalpy of formation (∆Hof) is zero for elements in their standard state.
      • Standard state: the most stable form of the element under standard conditions (298 K, 1 atm).
    • Question 3:
      • Calculate the enthalpy change (ΔH) for dissolving NaOH in water.
      • Use the provided information: mass of NaOH, mass of water, initial and final temperatures, and specific heat of water.
      • Remember that ΔH is negative for an exothermic reaction and positive for an endothermic reaction.
    • Question 4:
      • Calculate the work done in a compression process using the formula w = -PΔV.
      • Note that work is negative for compression (volume decreases).
      • Convert L-atm to J using 1 L-atm = 101.3 J.
    • Question 5:
      • Calculate the heat released in a reaction using the enthalpy of formation and the mass of the reactant.
      • Use the stoichiometry of the balanced reaction to relate moles of reactant to moles of product.
    • Question 6:
      • Understand which processes depend on the path taken, meaning the work or heat involved changes depending on how the change occurs.
    • Question 7:
      • Calculate the heat required to raise the temperature of an aluminum cube using the formula q = mCΔT.
      • Note that the specific heat of aluminum is given in J/g-C, so convert kg to g.
    • Question 8:
      • Understand the relationship between enthalpy of fusion and the heat required to melt a substance.
      • Use the enthalpy of fusion and the molar mass of mercury to calculate the heat needed to melt a certain amount of mercury.
    • Question 23:
      • Calculate ΔGrxn at a specific temperature.
      • Understand the relationship between ΔH, ΔS, and ΔG.
      • The equation ΔGrxn = ΔHrxn − TΔSrxn is important for this calculation.
    • Question 24:
      • Calculate ΔG for a reaction at non-standard conditions and understand the relationship between ΔG°, partial pressures, and Kp.
      • Utilize the equation ΔG = ΔG° + RT(ln Q), where Q is the reaction quotient.
    • Question 25:
      • Calculate the heat of reaction (ΔHorxn) for the combustion of phenol using calorimetry data.
      • Remember ΔHorxn = q / moles of phenol.
      • Ensure consistent units between the heat capacity of the calorimeter (kJ/°C) and the temperature change (°C).
    • Question 26:
      • Understand solubility and the relationship between Ksp and the concentration of ions in solution.
      • The lower the Ksp, the less soluble the salt.
      • The concentration of [Ag+] will be lowest in the salt with the smallest Ksp.

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    Description

    Prepare for Exam 2 in Chemistry 1202 with this quiz that covers critical topics such as entropy, enthalpy, Gibbs free energy, and calorimetry. You will need to apply various relevant equations and concepts to demonstrate your understanding in a closed note format. Test your knowledge and ensure a solid grasp of thermodynamics principles essential for success.

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