First Law of Thermodynamics in Chemical Reactions
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Questions and Answers

Which equation represents the behavior of an ideal gas?

  • PV = nRT (correct)
  • V = nRT
  • P = nRT
  • PV ≠ nRT
  • What is the value of the gas constant R in units of L atm K-1 mol-1?

  • 0.082 (correct)
  • 1.98722
  • 8.314
  • 0.083
  • Which type of variables are independent of the size of the system?

  • Density
  • Intensive variables (correct)
  • Pressure
  • Extensive variables
  • What kind of gas does not obey the PV = nRT equation?

    <p>Real gas</p> Signup and view all the answers

    If a variable x is a state function, what remains the same when going from State I to State II?

    <p>$\Delta x(a)$</p> Signup and view all the answers

    For any cyclic process, what is the value of $\Delta x$?

    <p>$0$</p> Signup and view all the answers

    Which region is characterized by properties such as Temperature, Pressure, and Volume?

    <p>System</p> Signup and view all the answers

    In which type of system can both energy and matter be exchanged between the system and its surroundings?

    <p>Open system</p> Signup and view all the answers

    What is the region outside the system and separated from the system by a boundary called?

    <p>Surroundings</p> Signup and view all the answers

    Which type of system allows only energy transfer, either as work or by heat transfer?

    <p>Isolated system</p> Signup and view all the answers

    Which type of system does not allow for the exchange of energy or matter?

    <p>Isolated system</p> Signup and view all the answers

    What is the term used for the organized form of energy transfer in thermodynamics?

    <p>Work</p> Signup and view all the answers

    Which method involves a 2-step reaction for the formation of CO2?

    <p>Method 2</p> Signup and view all the answers

    What is the standard enthalpy of formation of H2O (l) at 298 K?

    <p>-285.83 kJ mol-1</p> Signup and view all the answers

    What is the reference state of an element in standard enthalpies of formation?

    <p>Its most stable state at specified temperature and pressure</p> Signup and view all the answers

    What does Hess's law state about the enthalpy of formation of compounds?

    <p>It is additive and independent of the reaction path</p> Signup and view all the answers

    Which law is used to calculate the enthalpy change when substances are formed from their elements?

    <p>Hess's Law</p> Signup and view all the answers

    What is the relationship between enthalpy change (∆H) and internal energy change (∆U) in a chemical reaction according to the First Law of Thermodynamics?

    <p>∆H is always less than ∆U</p> Signup and view all the answers

    What does the equation qP = qV + RT(∆n) represent in the context of gas phase reactions?

    <p>The enthalpy change due to a change in the number of moles of gas reactants</p> Signup and view all the answers

    What is the purpose of a constant-volume bomb calorimeter in thermodynamic experiments?

    <p>To ensure no heat enters or leaves the system during a reaction</p> Signup and view all the answers

    What does the equation qcal =Ccal ∆t represent in the context of calorimetry?

    <p>The heat exchange during the reaction in a bomb calorimeter</p> Signup and view all the answers

    In a constant-pressure bomb calorimeter, what principle is used to relate the heat changes of the compound and water?

    <p>The law of conservation of energy</p> Signup and view all the answers

    For a combustion reaction in a constant-volume calorimeter, if q = 1364.34 kJ mol-1 at 298 K, what is the value being measured?

    <p>Enthalpy change of combustion</p> Signup and view all the answers

    What is the relationship between enthalpy change (∆H) and internal energy change (∆U) according to Hess's Law?

    <p>They are independent</p> Signup and view all the answers

    In a chemical reaction, if the enthalpy changes for the individual steps are known, what can be said about the overall enthalpy change according to Hess's Law?

    <p>It is equal to the sum of enthalpy changes for individual steps</p> Signup and view all the answers

    If a reaction takes place in a series of steps, what does the stoichiometric coefficients of product and reactant represent?

    <p>The smallest integers consistent with the reaction</p> Signup and view all the answers

    What role do enthalpy and internal energy play in chemical reactions according to the First Law of Thermodynamics?

    <p>They provide information about heat changes in reactions</p> Signup and view all the answers

    If a reaction has ∆n = -1, what can be concluded about the enthalpy change (∆H) based on the formula ∆H = ∆U + RT(∆n)?

    <p>∆H is negative</p> Signup and view all the answers

    Why is it important to consider enthalpy changes in chemical reactions?

    <p>To predict if a reaction is exothermic or endothermic</p> Signup and view all the answers

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