Answer :
Sure! Let's go through each question one by one:
Question 13: The thermodynamic state function that describes the heat absorbed by a system at constant pressure is called:
- A. Entropy: This is a measure of disorder or randomness in a system, not directly related to heat at constant pressure.
- B. Enthalpy: This is the correct answer. Enthalpy is a measure of the total energy of a thermodynamic system, and it's specifically related to heat changes at constant pressure.
- C. Calorimetry: This is a method of measuring heat, but it is not a thermodynamic state function.
- D. Work: This refers to energy transfer in the form of mechanical energy, not a state function related to heat at constant pressure.
Thus, the correct answer is B. Enthalpy.
Question 14: The mathematical expression for a reaction occurring at a constant pressure is:
- A. [tex]\(\Delta U = q_p - P \Delta V\)[/tex]: This is an expression related to internal energy, not directly associating enthalpy change.
- B. [tex]\(\Delta U = \Delta H\)[/tex]: Not true in general; this holds only under specific conditions.
- C. [tex]\(\Delta U = \Delta H + p \Delta V\)[/tex]: This relates to changes in internal energy, not directly to heat at constant pressure.
- D. [tex]\(\Delta H = q_p\)[/tex]: This is the correct answer, as it represents the enthalpy change ([tex]\(\Delta H\)[/tex]) being equal to the heat exchanged ([tex]\(q_p\)[/tex]) at constant pressure.
Thus, the correct answer is D. [tex]\(\Delta H = q_p\)[/tex].
Question 15: The enthalpy change of a reaction involving solids or liquids only can be expressed as:
- A. [tex]\(\Delta H = \Delta U\)[/tex]: This is often true for reactions involving only solids and liquids because the volume change is negligible, making pressure-volume work negligible.
- B. [tex]\(\Delta U = q_p\)[/tex]: Incorrect, as this relates to heat at constant pressure rather than directly describing enthalpy change when volume work is negligible.
- C. [tex]\(\Delta U = q_v\)[/tex]: Incorrect, this expression describes internal energy change at constant volume, not enthalpy at constant pressure.
- D. [tex]\(\Delta U = q_p-P \Delta V\)[/tex]: This equation typically accounts for overall internal energy changes, not directly applicable here to describe enthalpy.
Thus, the correct answer is A. [tex]\(\Delta H = \Delta U\)[/tex], as this often applies when only solids and liquids are involved in a reaction.
I hope this explanation helps you understand each question and its correct answer!
Question 13: The thermodynamic state function that describes the heat absorbed by a system at constant pressure is called:
- A. Entropy: This is a measure of disorder or randomness in a system, not directly related to heat at constant pressure.
- B. Enthalpy: This is the correct answer. Enthalpy is a measure of the total energy of a thermodynamic system, and it's specifically related to heat changes at constant pressure.
- C. Calorimetry: This is a method of measuring heat, but it is not a thermodynamic state function.
- D. Work: This refers to energy transfer in the form of mechanical energy, not a state function related to heat at constant pressure.
Thus, the correct answer is B. Enthalpy.
Question 14: The mathematical expression for a reaction occurring at a constant pressure is:
- A. [tex]\(\Delta U = q_p - P \Delta V\)[/tex]: This is an expression related to internal energy, not directly associating enthalpy change.
- B. [tex]\(\Delta U = \Delta H\)[/tex]: Not true in general; this holds only under specific conditions.
- C. [tex]\(\Delta U = \Delta H + p \Delta V\)[/tex]: This relates to changes in internal energy, not directly to heat at constant pressure.
- D. [tex]\(\Delta H = q_p\)[/tex]: This is the correct answer, as it represents the enthalpy change ([tex]\(\Delta H\)[/tex]) being equal to the heat exchanged ([tex]\(q_p\)[/tex]) at constant pressure.
Thus, the correct answer is D. [tex]\(\Delta H = q_p\)[/tex].
Question 15: The enthalpy change of a reaction involving solids or liquids only can be expressed as:
- A. [tex]\(\Delta H = \Delta U\)[/tex]: This is often true for reactions involving only solids and liquids because the volume change is negligible, making pressure-volume work negligible.
- B. [tex]\(\Delta U = q_p\)[/tex]: Incorrect, as this relates to heat at constant pressure rather than directly describing enthalpy change when volume work is negligible.
- C. [tex]\(\Delta U = q_v\)[/tex]: Incorrect, this expression describes internal energy change at constant volume, not enthalpy at constant pressure.
- D. [tex]\(\Delta U = q_p-P \Delta V\)[/tex]: This equation typically accounts for overall internal energy changes, not directly applicable here to describe enthalpy.
Thus, the correct answer is A. [tex]\(\Delta H = \Delta U\)[/tex], as this often applies when only solids and liquids are involved in a reaction.
I hope this explanation helps you understand each question and its correct answer!
