MCQ Chemistry Unit 5: Chemical Thermodynamics, HS 1st year

 

MCQs on Thermodynamics

1. Which of the following systems allows the exchange of both energy and matter with its surroundings?

   • A) Closed system
   • B) Isolated system
   • C) Open system
   • D) Adiabatic system
   • Answer: C) Open system

2. What is the term for the heat change at constant pressure?

   • A) Internal energy
   • B) Enthalpy
   • C) Entropy
   • D) Work
   • Answer: B) Enthalpy

3. What does the first law of thermodynamics state?

   • A) Energy can be created or destroyed.
   • B) The energy of an isolated system is constant.
   • C) Entropy of the universe always increases.
   • D) Energy is dependent on the path taken.
   • Answer: B) The energy of an isolated system is constant.

4. Which property of a system does NOT depend on the size or amount of material?

   • A) Volume
   • B) Mass
   • C) Temperature
   • D) Enthalpy
   • Answer: C) Temperature

5. In an adiabatic process, which of the following remains constant?

   • A) Temperature
   • B) Pressure
   • C) Heat exchange
   • D) Volume
   • Answer: C) Heat exchange

6. The enthalpy change when one mole of a substance is formed from its elements in their standard states is called:

   • A) Heat of combustion
   • B) Standard enthalpy of formation
   • C) Lattice energy
   • D) Bond enthalpy
   • Answer: B) Standard enthalpy of formation

7. Which of the following is a state function?

   • A) Work
   • B) Heat
   • C) Enthalpy
   • D) Distance
   • Answer: C) Enthalpy

8. What is the correct expression for the first law of thermodynamics?

   • A) ∆U = q + w
   • B) ∆U = q - w
   • C) ∆U = -q + w
   • D) ∆U = -q - w
   • Answer: A) ∆U = q + w

9. The heat required to raise the temperature of one mole of a substance by one degree is called:

   • A) Specific heat capacity
   • B) Molar heat capacity
   • C) Heat of reaction
   • D) Latent heat
   • Answer: B) Molar heat capacity

10. Which of the following equations is used to calculate work done in an isothermal reversible expansion of an ideal gas?

• A) $w = -P \Delta V$
• B) $w = -nRT \ln \frac{V_f}{V_i}$
• C) $w = P \Delta V$
• D) $w = q + \Delta U$
• Answer: B) $w = -nRT \ln \frac{V_f}{V_i}$

11. What type of wall does an adiabatic system have?

    • A) Thermally conducting
    • B) Thermally insulating
    • C) Permeable
    • D) Rigid
    • Answer: B) Thermally insulating

12. Which property represents the total energy of a system, including all forms such as chemical, electrical, and mechanical?

    • A) Enthalpy
    • B) Internal energy
    • C) Gibbs energy
    • D) Work
    • Answer: B) Internal energy

13. For which type of process is $\Delta U = 0$?

    • A) Isothermal process
    • B) Adiabatic process
    • C) Isobaric process
    • D) Isochoric process
    • Answer: A) Isothermal process

14. What does the term $\Delta G$ (Gibbs free energy) indicate for a process?

    • A) Energy conservation
    • B) Spontaneity of the process
    • C) Reaction rate
    • D) Heat transfer
    • Answer: B) Spontaneity of the process

15. What happens to entropy in a reversible process?

    • A) It decreases.
    • B) It increases.
    • C) It remains constant.
    • D) It depends on pressure.
    • Answer: C) It remains constant.

16. Which of the following is a path function?

    • A) Enthalpy
    • B) Entropy
    • C) Work
    • D) Pressure
    • Answer: C) Work

17. Which law of thermodynamics states that energy cannot be created or destroyed?

    • A) First law
    • B) Second law
    • C) Third law
    • D) Zeroth law
    • Answer: A) First law

18. If $\Delta G < 0$, what can be said about the process?

    • A) It is non-spontaneous.
    • B) It is at equilibrium.
    • C) It is spontaneous.
    • D) It violates thermodynamic laws.
    • Answer: C) It is spontaneous.

19. In the reaction $C(s) + O_2(g) \rightarrow CO_2(g)$, the enthalpy change is negative. What type of reaction is this?

    • A) Endothermic
    • B) Exothermic
    • C) Spontaneous
    • D) Isothermal
    • Answer: B) Exothermic

20. Which of the following quantities depends on the path taken during a process?

    • A) Internal energy
    • B) Work
    • C) Enthalpy
    • D) Entropy
    • Answer: B) Work

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Advanced Thermodynamic Questions

21. What does Hess's Law help to calculate?

    • A) Pressure changes
    • B) Reaction enthalpy
    • C) Entropy changes
    • D) Gibbs energy
    • Answer: B) Reaction enthalpy

22. Which process occurs infinitely slowly, maintaining the system in equilibrium at all times?

    • A) Irreversible process
    • B) Reversible process
    • C) Adiabatic process
    • D) Spontaneous process
    • Answer: B) Reversible process

23. Which system type has no exchange of energy or matter with its surroundings?

    • A) Closed
    • B) Open
    • C) Isolated
    • D) Adiabatic
    • Answer: C) Isolated

24. What is the mathematical expression for the first law of thermodynamics in an isochoric process?

    • A) $\Delta U = q_V$
    • B) $\Delta U = q - w$
    • C) $\Delta U = q + w$
    • D) $\Delta U = -q$
    • Answer: A) $\Delta U = q_V$

25. Which of the following is NOT an extensive property?

    • A) Volume
    • B) Mass
    • C) Density
    • D) Internal energy
    • Answer: C) Density

26. What does the equation $\Delta H = \Delta U + p \Delta V$ represent?

    • A) The relationship between heat and work
    • B) The relationship between enthalpy and internal energy
    • C) The conservation of energy
    • D) The second law of thermodynamics
    • Answer: B) The relationship between enthalpy and internal energy

27. Which process has $\Delta q = 0$?

    • A) Adiabatic
    • B) Isothermal
    • C) Isochoric
    • D) Isobaric
    • Answer: A) Adiabatic

28. The heat capacity at constant pressure is denoted by which symbol?

    • A) $C_v$
    • B) $C_p$
    • C) $q$
    • D) $H$
    • Answer: B) $C_p$

29. Which quantity determines the extent of disorder in a system?

    • A) Enthalpy
    • B) Entropy
    • C) Internal energy
    • D) Gibbs energy
    • Answer: B) Entropy

30. What is the standard state of a substance?

    • A) Pure form at 0°C
    • B) Pure form at 25°C and 1 atm pressure
    • C) Pure form at 100°C and 1 atm pressure
    • D) Pure form at any pressure
    • Answer: B) Pure form at 25°C and 1 atm pressure

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Numerical and Conceptual Questions

31. The heat absorbed at constant volume is equivalent to:

    • A) $\Delta H$
    • B) $q_p$
    • C) $\Delta U$
    • D) Work
    • Answer: C) $\Delta U$

32. For an ideal gas, what is the relationship between $C_p$ and $C_v$?

    • A) $C_p > C_v$
    • B) $C_p < C_v$
    • C) $C_p = C_v$
    • D) $C_p + C_v = R$
    • Answer: A) $C_p > C_v$

33. Which type of calorimeter is used to measure $q_v$?

    • A) Bomb calorimeter
    • B) Coffee cup calorimeter
    • C) Adiabatic calorimeter
    • D) Isothermal calorimeter
    • Answer: A) Bomb calorimeter

34. The number of moles of gaseous products minus the number of moles of gaseous reactants is denoted by:

    • A) $\Delta n_g$
    • B) $\Delta G$
    • C) $\Delta U$
    • D) $\Delta H$
    • Answer: A) $\Delta n_g$

35. What is the heat required to raise the temperature of 1g of a substance by 1°C?

    • A) Heat capacity
    • B) Molar heat capacity
    • C) Specific heat capacity
    • D) Thermal conductivity
    • Answer: C) Specific heat capacity

36. What is the enthalpy change when 1 mole of a solid turns into its vapor without passing through the liquid phase?

    • A) $\Delta H_{\text{fusion}}$
    • B) $\Delta H_{\text{vaporization}}$
    • C) $\Delta H_{\text{sublimation}}$
    • D) $\Delta H_{\text{combustion}}$
    • Answer: C) $\Delta H_{\text{sublimation}}$

37. What is the bond enthalpy of $O = O$?

    • A) 498 kJ/mol
    • B) 418 kJ/mol
    • C) 436 kJ/mol
    • D) 946 kJ/mol
    • Answer: A) 498 kJ/mol

38. In free expansion of an ideal gas, the work done is:

    • A) Positive
    • B) Negative
    • C) Zero
    • D) Infinity
    • Answer: C) Zero

39. What is the molar enthalpy of vaporization for water at 298 K?

    • A) 40.79 kJ/mol
    • B) 44.01 kJ/mol
    • C) 25.2 kJ/mol
    • D) 37.9 kJ/mol
    • Answer: B) 44.01 kJ/mol

40. What is the unit of Gibbs free energy?

• A) Joule
• B) Joule per mole
• C) Calorie
• D) Kilogram
• Answer: B) Joule per mole

১. তাপগতিবিদ্যা (Thermodynamics)

• পরিভাষা এবং গুরুত্ব:
  • বিভিন্ন শক্তি রূপান্তর ও তাদের প্রক্রিয়া বিশ্লেষণ তাপগতিবিদ্যার মূল বিষয়বস্তু।
  • এটি কোনো প্রক্রিয়া কি স্বতঃস্ফূর্ত হবে কিনা এবং তার পরিমাণগত পরিবর্তন নির্ধারণ করতে ব্যবহৃত হয়।
• তাপগতিবিদ্যার মৌলিক আইন:
  • প্রথম আইন শক্তি সংরক্ষণকে নির্দেশ করে: শক্তি তৈরি বা ধ্বংস হয় না, কেবল স্থানান্তর হয়।
  • সিস্টেমের অন্তর্গত শক্তির পরিবর্তন নির্ধারণের সূত্র: ΔU = q + w।

২. সিস্টেম এবং পরিবেশ (System and Surroundings)

• সিস্টেম প্রকারভেদ:
  • খোলা সিস্টেম (Open System): শক্তি এবং পদার্থ পরিবেশের সাথে বিনিময় করে।
  • বন্ধ সিস্টেম (Closed System): কেবল শক্তি বিনিময় করতে পারে, পদার্থ নয়।
  • বিচ্ছিন্ন সিস্টেম (Isolated System): শক্তি বা পদার্থ বিনিময় করে না।

৩. অন্তর্গত শক্তি এবং কাজ (Internal Energy and Work)

• অন্তর্গত শক্তি:
  • সিস্টেমের সমস্ত শক্তির যোগফল।
  • তাপ এবং কাজের মাধ্যমে শক্তি পরিবর্তন হয়।
• কাজের সংজ্ঞা:
  • চাপ ও ভলিউমের উপর ভিত্তি করে কাজ নির্ধারণ: $w = -P_{ext} \Delta V$।

৪. এন্টালপি ও তাপ ধারণ ক্ষমতা (Enthalpy and Heat Capacity)

• এন্টালপি (H):
  • সিস্টেমের চাপ-স্থির অবস্থায় তাপ শোষণ বা নির্গমনের পরিমাপ।
  • এন্টালপি পরিবর্তন: $\Delta H = \Delta U + P\Delta V$।
• তাপ ধারণ ক্ষমতা:
  • নির্দিষ্ট তাপ ধারণ ক্ষমতা: একটি বস্তু প্রতি ইউনিট ভরের তাপমাত্রা ১ ডিগ্রি বাড়াতে যত শক্তি লাগে।

৫. রিঅ্যাকশন এন্টালপি এবং হেস-এর সূত্র (Reaction Enthalpy and Hess's Law)

• প্রতিক্রিয়া এন্টালপি:
  • $\Delta_r H = \Sigma H_{\text{প্রোডাক্ট}} - \Sigma H_{\text{রিঅ্যাক্ট্যান্ট}}$।
• হেস-এর সূত্র:
  • কোনো রাসায়নিক পরিবর্তনের এন্টালপি পরিবর্তন তার সরাসরি বা ধাপে ধাপে সম্পাদিত প্রক্রিয়ার উপর নির্ভর করে না।

৬. বিভিন্ন ধরণের এন্টালপি পরিবর্তন

• গলন, বাষ্পীকরণ ও উপসাগরিত এন্টালপি:
  • গলনের জন্য তাপ: $\Delta_{\text{fus}}H$।
  • বাষ্পীকরণের জন্য তাপ: $\Delta_{\text{vap}}H$।
  • স্ফটিকের গ্যাসে পরিবর্তনের জন্য তাপ: $\Delta_{\text{sub}}H$।

৭. বন্ধন এন্টালপি (Bond Enthalpy)

• সংজ্ঞা:
  • এক মোল গ্যাসীয় বন্ধন ভাঙার জন্য প্রয়োজনীয় তাপ।
• গড় বন্ধন এন্টালপি: বহুপারমাণবিক অণুর ক্ষেত্রে ব্যবহৃত হয়।

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