MCQ Chemistry Unit 6: Equilibrium, HS 1st Year

 

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1. Which of the following is true about a system at equilibrium?
A. The rates of the forward and reverse reactions are equal.
B. The concentrations of reactants and products are equal.
C. The reaction has stopped.
D. Only the forward reaction occurs.

Answer: A

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2. What is the equilibrium constant expression for the reaction $H_2(g) + I_2(g) \leftrightarrow 2HI(g)$?
A. $K_c = \frac{[H_2][I_2]}{[HI]^2}$
B. $K_c = \frac{[HI]^2}{[H_2][I_2]}$
C. $K_c = [H_2][I_2][HI]$
D. $K_c = \frac{[HI]}{[H_2][I_2]}$

Answer: B

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3. What does Le Chatelier's principle state about a system at equilibrium when a stress is applied?
A. The system shifts to oppose the stress and restore equilibrium.
B. The system remains unaffected by the stress.
C. The forward reaction stops entirely.
D. The reverse reaction stops entirely.

Answer: A

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4. What happens to the equilibrium position when the concentration of a reactant is increased?
A. Equilibrium shifts to the right to form more products.
B. Equilibrium shifts to the left to form more reactants.
C. Equilibrium remains unchanged.
D. The system decomposes completely.

Answer: A

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5. In the equilibrium $CaCO_3(s) \leftrightarrow CaO(s) + CO_2(g)$, what happens if the pressure is increased?
A. More $CO_2$ is produced.
B. The equilibrium shifts to the left, favoring $CaCO_3$.
C. The equilibrium shifts to the right, favoring $CaO$ and $CO_2$.
D. The equilibrium remains unaffected.

Answer: B

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6. Which statement is correct regarding dynamic equilibrium?
A. No reactions occur in either direction.
B. The system must be open to the environment.
C. The concentrations of reactants and products do not change with time.
D. The forward reaction rate decreases over time while the reverse rate increases.

Answer: C

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7. According to Henry's law, the solubility of a gas in a liquid is directly proportional to:
A. Temperature of the liquid.
B. Pressure of the gas above the liquid.
C. Volume of the liquid.
D. Nature of the gas.

Answer: B

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8. For a reaction $A + B \leftrightarrow C + D$, if the equilibrium constant $K_c$ is very large, which of the following is true?
A. Reactants dominate in the equilibrium mixture.
B. Products dominate in the equilibrium mixture.
C. The reaction does not proceed significantly.
D. The reaction is at dynamic equilibrium.

Answer: B

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9. What is the equilibrium constant expression for the reaction $2SO_2(g) + O_2(g) \leftrightarrow 2SO_3(g)$?
A. $K_c = \frac{[SO_3]^2}{[SO_2]^2[O_2]}$
B. $K_c = \frac{[SO_2]^2[O_2]}{[SO_3]^2}$
C. $K_c = [SO_3]^2[SO_2]^2$
D. $K_c = [SO_3]/[SO_2][O_2]$

Answer: A

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10. Which of the following factors does NOT affect the equilibrium constant?
A. Concentration of reactants
B. Temperature
C. Nature of the reaction
D. Catalyst

Answer: D

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11. The equilibrium constant for the reaction $N_2(g) + 3H_2(g) \leftrightarrow 2NH_3(g)$ is $K_p$. What happens to $K_p$ if the reaction is reversed?
A. $K_p$ remains unchanged.
B. $K_p$ is squared.
C. $K_p$ is halved.
D. $K_p$ becomes $\frac{1}{K_p}$.

Answer: D

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12. Which of the following is true for a saturated solution of sugar in water?
A. No dynamic equilibrium exists.
B. Rate of dissolution equals rate of crystallization.
C. Only dissolution occurs.
D. Rate of crystallization is higher than the rate of dissolution.

Answer: B

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13. Which process represents a solid-vapour equilibrium?
A. Ice melting to water
B. Iodine subliming to vapour
C. Water evaporating to vapour
D. Salt dissolving in water

Answer: B

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14. The equilibrium constant $K_p$ and $K_c$ are related by the equation $K_p = K_c(RT)^{\Delta n}$. What does $\Delta n$ represent?
A. Number of moles of products
B. Number of moles of reactants
C. Change in the number of moles of gas
D. Total number of moles at equilibrium

Answer: C

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15. In a chemical equilibrium, which of the following is true for Gibbs free energy ($\Delta G$)?
A. $\Delta G > 0$
B. $\Delta G < 0$
C. $\Delta G = 0$
D. $\Delta G$ keeps changing

Answer: C

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16. According to Le Chatelier’s principle, what happens if the temperature is increased for an exothermic reaction?
A. Equilibrium shifts to the right.
B. Equilibrium shifts to the left.
C. No change in equilibrium.
D. Both directions are equally favored.

Answer: B

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17. What happens when a catalyst is added to a reaction at equilibrium?
A. Increases the equilibrium constant
B. Decreases the equilibrium constant
C. Speeds up both the forward and reverse reactions equally
D. Shifts the equilibrium position

Answer: C

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18. In the reaction $H_2(g) + I_2(g) \leftrightarrow 2HI(g)$, what happens if iodine is removed?
A. The equilibrium shifts to the left.
B. The equilibrium shifts to the right.
C. No effect on the equilibrium.
D. Reaction stops completely.

Answer: B

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19. Henry’s law relates the solubility of a gas to:
A. Its molar mass
B. The pressure of the gas
C. The temperature of the solution
D. The volume of the gas

Answer: B

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20. For the equilibrium $CO(g) + H_2O(g) \leftrightarrow CO_2(g) + H_2(g)$, the value of $K_c$ is 4.24 at 800 K. What does this imply?
A. Products are favored at equilibrium.
B. Reactants are favored at equilibrium.
C. The reaction does not proceed significantly.
D. The system is at static equilibrium.

Answer: A

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21. In a closed system at equilibrium, which of the following changes can alter the equilibrium position?
A. Addition of a catalyst
B. Change in temperature
C. Increasing the volume of the system for a gaseous reaction
D. Both B and C

Answer: D

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22. For the equilibrium $H_2O(l) \leftrightarrow H_2O(vap)$, which factor increases the equilibrium vapor pressure?
A. Adding more liquid water
B. Increasing the temperature
C. Decreasing the temperature
D. Increasing the volume of the container

Answer: B

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23. The law of chemical equilibrium states that at a given temperature:
A. All reactions proceed to completion.
B. The ratio of the product of concentrations of products to reactants raised to their stoichiometric coefficients is constant.
C. The concentration of reactants equals that of products.
D. Reactants and products have equal moles.

Answer: B

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24. For the equilibrium $2NO(g) + Cl_2(g) \leftrightarrow 2NOCl(g)$, what happens if the pressure is decreased?
A. Equilibrium shifts to the right.
B. Equilibrium shifts to the left.
C. Equilibrium is unchanged.
D. Reaction rate decreases.

Answer: B

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25. What is the effect of increasing temperature on the solubility of a gas in a liquid?
A. Solubility increases.
B. Solubility decreases.
C. Solubility remains unchanged.
D. It depends on the gas.

Answer: B

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26. In a dynamic equilibrium, the forward and reverse reactions:
A. Occur at the same rate.
B. Stop completely.
C. Are unequal in rate.
D. Favor reactants over products.

Answer: A

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27. What is the relationship between the equilibrium constant $K_c$ and the rate constants $k_f$ (forward reaction) and $k_r$ (reverse reaction)?
A. $K_c = k_f \times k_r$
B. $K_c = k_r / k_f$
C. $K_c = k_f / k_r$
D. $K_c = k_f + k_r$

Answer: C

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28. For the reaction $CaCO_3(s) \leftrightarrow CaO(s) + CO_2(g)$, what does $K_p$ represent?
A. Total pressure in the system
B. Pressure of $CO_2$ at equilibrium
C. Concentration of $CaCO_3$
D. Partial pressure of $CaO$

Answer: B

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29. In the equilibrium $H_2(g) + I_2(g) \leftrightarrow 2HI(g)$, which condition favors the formation of HI?
A. Increasing the concentration of $H_2$
B. Removing $HI$ as it forms
C. Increasing pressure
D. All of the above

Answer: D

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30. Which type of equilibrium is characterized by the coexistence of different phases?
A. Homogeneous equilibrium
B. Heterogeneous equilibrium
C. Static equilibrium
D. None of the above

Answer: B

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31. The equilibrium constant $K_c$ for the reaction $2HI \leftrightarrow H_2 + I_2$ is 0.04 at a certain temperature. What does this imply?
A. Products are favored at equilibrium.
B. Reactants are favored at equilibrium.
C. The reaction proceeds to completion.
D. Both reactants and products are present in equal amounts.

Answer: B

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32. Which of the following processes is an example of physical equilibrium?
A. Sublimation of iodine in a closed container
B. Dissolution of salt in water
C. Formation of $NH_3$ from $N_2$ and $H_2$
D. Decomposition of $CaCO_3$

Answer: A

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33. For the reaction $N_2 + 3H_2 \leftrightarrow 2NH_3$, if the temperature is increased, the equilibrium constant $K_c$:
A. Increases
B. Decreases
C. Remains constant
D. Cannot be determined

Answer: B

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34. What is the unit of $K_c$ for the reaction $2A \leftrightarrow B$?
A. No unit
B. $\text{mol/L}$
C. $(\text{mol/L})^{-1}$
D. $(\text{mol/L})^2$

Answer: C

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35. Which of the following does Henry’s law fail to apply to?
A. Oxygen in water
B. Carbon dioxide in soda
C. Hydrogen in organic solvents
D. Ammonia in water

Answer: D

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36. In a chemical equilibrium, if $Q_c < K_c$, the reaction proceeds:
A. In the forward direction
B. In the reverse direction
C. Equilibrium is already achieved
D. Reaction stops

Answer: A

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37. For the reaction $2NOCl(g) \leftrightarrow 2NO(g) + Cl_2(g)$, increasing pressure will:
A. Shift equilibrium to the right
B. Shift equilibrium to the left
C. Have no effect
D. Increase reaction rate

Answer: B

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38. At equilibrium, the concentrations of $H_2, I_2,$ and $HI$ in a reaction vessel are 0.2 M, 0.2 M, and 0.6 M, respectively. Calculate $K_c$ for the reaction $H_2 + I_2 \leftrightarrow 2HI$.
A. 9
B. 3
C. 6
D. 1

Answer: A
(Solution: $K_c = [HI]^2 / [H_2][I_2] = (0.6)^2 / (0.2)(0.2) = 9$)

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39. The addition of an inert gas to a gaseous equilibrium mixture at constant volume:
A. Shifts the equilibrium to the right
B. Shifts the equilibrium to the left
C. Has no effect on the equilibrium
D. Decreases the equilibrium constant

Answer: C

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40. The pH scale is used to measure:
A. Concentration of hydroxide ions
B. Concentration of hydrogen ions
C. Concentration of both $H^+$ and $OH^-$ ions
D. Ionic product of water

Answer: B

১. ভারসাম্য (Equilibrium) পরিচিতি

• ভারসাম্যের ধারণা পদার্থবিজ্ঞানের বিভিন্ন প্রক্রিয়া ও রাসায়নিক বিক্রিয়ায় ব্যবহৃত হয়।
• ভারসাম্য একটি গতিশীল অবস্থার পরিচায়ক, যেখানে ফরওয়ার্ড ও ব্যাকওয়ার্ড বিক্রিয়ার হার সমান।

২. পদার্থগত ভারসাম্য (Physical Equilibrium)

ক. কঠিন-তরল ভারসাম্য

• নির্দিষ্ট তাপমাত্রায় বরফ এবং পানি একটি নির্দিষ্ট স্থানে ভারসাম্য অবস্থায় থাকে।
• তাপমাত্রা ও চাপে নির্ভর করে।

খ. তরল-বাষ্প ভারসাম্য

• নির্দিষ্ট তাপমাত্রায় তরলের বাষ্প চাপ নির্দিষ্ট হয়।
• বিভিন্ন তরলের জন্য বাষ্প চাপ আলাদা হয়, যা তাদের অস্থিরতার উপর নির্ভর করে।

গ. কঠিন-বাষ্প ভারসাম্য

• কঠিন পদার্থ যেমন আয়োডিনের বাষ্পে রূপান্তর এবং পুনঃগঠনের মাধ্যমে ভারসাম্য স্থাপিত হয়।

ঘ. কঠিন বা গ্যাসের দ্রবণীয়তা

• নির্দিষ্ট তাপমাত্রায় একটি দ্রবণে দ্রাবক ও দ্রব্যের মধ্যে ভারসাম্য থাকে।
• হেনরি'স সূত্র অনুযায়ী গ্যাসের দ্রবণীয়তা চাপের সাথে আনুপাতিক।

৩. রাসায়নিক ভারসাম্য (Chemical Equilibrium)

ক. গতি এবং প্রকৃতি

• রাসায়নিক বিক্রিয়া ফরওয়ার্ড এবং ব্যাকওয়ার্ড দুটি দিকেই ঘটে।
• উদাহরণ: Haber’s প্রক্রিয়ায় অ্যামোনিয়া সংশ্লেষণ।

খ. রাসায়নিক ভারসাম্যের সূত্র

• Guldberg এবং Waage এর সূত্র অনুযায়ী, ভারসাম্য স্থিতিতে বিক্রিয়ক ও পণ্যের ঘনত্বের অনুপাত নির্দিষ্ট থাকে: $$K_c = \frac{[পণ্য]}{[বিক্রিয়ক]}$$

গ. প্রভাবিতকারী বিষয়

• তাপমাত্রা, চাপ, এবং ঘনত্ব পরিবর্তন ভারসাম্যের উপর প্রভাব ফেলে।
• Le Chatelier’s নীতিমালা এই পরিবর্তনগুলো ব্যাখ্যা করে।

৪. ব্যবহার এবং গণনা

ক. ভারসাম্যের স্থিতি নির্ণয়

• $K_c$ এর মান বড় হলে পণ্য প্রধান হয়, আর ছোট হলে বিক্রিয়ক প্রধান হয়।

খ. রাসায়নিক প্রতিক্রিয়া প্রবাহ অনুমান

• বিক্রিয়ার প্রবাহ $Q_c$ এবং $K_c$ এর তুলনা করে নির্ধারণ করা হয়।

গ. ভারসাম্যের ঘনত্ব গণনা

• প্রাথমিক ঘনত্ব থেকে ভারসাম্যের ঘনত্ব গণনা করা হয় স্টোকিওমেট্রি ব্যবহার করে।

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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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MCQ Chemistry Unit 4: Chemical Bonding and Molecular Structure, HS 1st Year

 

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1. According to the Kössel-Lewis approach, what is the primary force that holds atoms together in a molecule?
A) Magnetic force
B) Electrostatic attraction
C) Gravitational pull
D) Nuclear binding force
Answer: B) Electrostatic attraction

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2. What does the octet rule state about chemical bonding?
A) Atoms share electrons to form a pair.
B) Atoms lose or gain electrons to achieve eight electrons in their valence shell.
C) Atoms share or transfer electrons to have a total of eight valence shells.
D) Atoms form bonds to minimize their energy.
Answer: B) Atoms lose or gain electrons to achieve eight electrons in their valence shell.

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3. Which type of bond is formed when electrons are shared equally between two atoms?
A) Polar covalent bond
B) Nonpolar covalent bond
C) Ionic bond
D) Metallic bond
Answer: B) Nonpolar covalent bond

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4. What is the shape of the CH4 molecule according to the VSEPR theory?
A) Trigonal planar
B) Linear
C) Tetrahedral
D) Pyramidal
Answer: C) Tetrahedral

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5. What is the primary reason for deviations in bond angles in molecules like NH3 and H2O?
A) Lone pair-lone pair repulsion
B) Lone pair-bond pair repulsion
C) Bond pair-bond pair repulsion
D) None of the above
Answer: B) Lone pair-bond pair repulsion

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6. Which of the following elements typically exhibits an incomplete octet in its compounds?
A) Carbon
B) Boron
C) Nitrogen
D) Oxygen
Answer: B) Boron

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7. In molecular orbital theory, what is the bond order of the N2 molecule?
A) 1
B) 2
C) 3
D) 4
Answer: C) 3

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8. How is the dipole moment mathematically defined?
A) µ = charge (Q) × distance (r)
B) µ = Q / r
C) µ = Q × 2πr
D) µ = Q² / r
Answer: A) µ = charge (Q) × distance (r)

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9. What is the type of bond formed by the sideways overlap of p-orbitals?
A) Sigma bond
B) Pi bond
C) Ionic bond
D) Hydrogen bond
Answer: B) Pi bond

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10. In resonance structures, what do formal charges help determine?
A) The total number of electrons in a molecule
B) The stability of the molecule
C) The molecular geometry
D) The number of bonds in a molecule
Answer: B) The stability of the molecule

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11. Which type of bond is formed when there is a transfer of electrons between two atoms?
A) Ionic bond
B) Covalent bond
C) Metallic bond
D) Hydrogen bond
Answer: A) Ionic bond

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12. The formation of NaCl involves which of the following processes?
A) Sharing of electrons
B) Transfer of electrons from Na to Cl
C) Sharing of protons between Na and Cl
D) Formation of hydrogen bonds
Answer: B) Transfer of electrons from Na to Cl

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13. In which molecule does the octet rule fail due to an odd number of electrons?
A) H2O
B) NH3
C) NO
D) CH4
Answer: C) NO

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14. What is the primary concept behind VSEPR theory?
A) Atoms repel one another equally in molecules.
B) Electron pairs in the valence shell repel one another to minimize repulsion.
C) Protons in the nucleus dictate molecular geometry.
D) Bonds form solely to stabilize energy levels.
Answer: B) Electron pairs in the valence shell repel one another to minimize repulsion.

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15. Which of the following is an example of a molecule with a linear shape?
A) CH4
B) CO2
C) NH3
D) H2O
Answer: B) CO2

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16. What type of hybridization is present in methane (CH4)?
A) sp
B) sp2
C) sp3
D) sp3d
Answer: C) sp3

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17. In which compound is the central atom surrounded by more than eight electrons (expanded octet)?
A) NH3
B) H2O
C) SF6
D) CH4
Answer: C) SF6

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18. What is the bond angle in a perfect tetrahedral molecule?
A) 90°
B) 104.5°
C) 109.5°
D) 120°
Answer: C) 109.5°

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19. What is the shape of a molecule with the molecular formula AB2E2?
A) Linear
B) Trigonal planar
C) Bent
D) Tetrahedral
Answer: C) Bent

---

20. What kind of bond is formed by the head-on overlap of orbitals?
A) Sigma bond
B) Pi bond
C) Ionic bond
D) Metallic bond
Answer: A) Sigma bond

---

21. Which theory explains the geometry of a molecule by considering the repulsion between electron pairs?
A) Valence Bond Theory
B) Molecular Orbital Theory
C) VSEPR Theory
D) Octet Theory
Answer: C) VSEPR Theory

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22. What is the formal charge of oxygen in the ozone molecule (O3)?
A) 0
B) -1
C) +1
D) Depends on the structure
Answer: D) Depends on the structure

---

23. How many valence electrons are there in the CO3²⁻ ion?
A) 20
B) 24
C) 28
D) 30
Answer: B) 24

---

24. What kind of bond is formed in a diatomic nitrogen molecule (N2)?
A) Single bond
B) Double bond
C) Triple bond
D) Ionic bond
Answer: C) Triple bond

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25. Which of the following is true about resonance structures?
A) They are separate molecules that interconvert rapidly.
B) The real structure is a hybrid of all canonical forms.
C) They only apply to ionic compounds.
D) Resonance structures have real physical existence.
Answer: B) The real structure is a hybrid of all canonical forms.

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26. Which molecule has zero dipole moment?
A) H2O
B) NH3
C) CH4
D) CHCl3
Answer: C) CH4

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27. The dipole moment of water (H2O) is due to which of the following?
A) Linear molecular geometry
B) Bent molecular geometry
C) Presence of double bonds
D) Presence of triple bonds
Answer: B) Bent molecular geometry

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28. Which statement is true about bond length?
A) It decreases as bond order increases.
B) It increases as bond order increases.
C) It is always the same for single, double, and triple bonds.
D) It is independent of bond strength.
Answer: A) It decreases as bond order increases.

---

29. Which molecule exhibits sp2 hybridization?
A) BF3
B) NH3
C) H2O
D) C2H6
Answer: A) BF3

---

30. Which of the following has the shortest bond length?
A) C-C
B) C=C
C) C≡C
D) C-H
Answer: C) C≡C

---

31. What is the bond order of O2 in its ground state?
A) 1
B) 2
C) 3
D) 4
Answer: B) 2

---

32. Which of the following does NOT obey the octet rule?
A) CH4
B) H2O
C) BeH2
D) NH3
Answer: C) BeH2

---

33. What is the geometry of SF6?
A) Tetrahedral
B) Trigonal planar
C) Octahedral
D) Square planar
Answer: C) Octahedral

---

34. What is the hybridization of the central atom in PCl5?
A) sp3
B) sp2
C) sp3d
D) sp3d2
Answer: C) sp3d

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35. Which of the following bonds is the strongest?
A) Single bond
B) Double bond
C) Triple bond
D) Hydrogen bond
Answer: C) Triple bond

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36. What is the molecular shape of NH3?
A) Linear
B) Trigonal planar
C) Trigonal pyramidal
D) Tetrahedral
Answer: C) Trigonal pyramidal

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37. What is the geometry of the carbonate ion (CO3²⁻)?
A) Linear
B) Trigonal planar
C) Tetrahedral
D) Bent
Answer: B) Trigonal planar

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38. Which of the following has the largest bond angle?
A) NH3
B) H2O
C) CH4
D) CO2
Answer: D) CO2

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39. What is the reason for the lower dipole moment in NF3 compared to NH3?
A) Lone pair orientation
B) Higher electronegativity of fluorine
C) Absence of hydrogen bonds
D) Non-linear structure of NF3
Answer: A) Lone pair orientation

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40. Which type of orbital overlap leads to the formation of a pi bond?
A) Axial overlap
B) Sidewise overlap
C) Spherical overlap
D) Radial overlap
Answer: B) Sidewise overlap

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১. রাসায়নিক বন্ধন ও অণুর গঠন

• রাসায়নিক বন্ধন সংজ্ঞা ও গুরুত্ব: বিভিন্ন পরমাণুর মধ্যে আকর্ষণ শক্তি রাসায়নিক বন্ধন নামে পরিচিত। রাসায়নিক বন্ধনের মাধ্যমে স্থিতিশীল অণু তৈরি হয়।
• কোসেল-লুইস পদ্ধতি: ১৯১৬ সালে রাসায়নিক বন্ধনের ইলেকট্রনিক তত্ত্বটি ব্যাখ্যা করে। এটি অক্টেট নিয়ম প্রতিষ্ঠা করে, যেখানে একটি পরমাণুর বহিঃস্তরে ৮টি ইলেকট্রন থাকলে সেটি স্থিতিশীল হয়।
• অক্টেট নিয়ম: ইলেকট্রন স্থানান্তর বা ভাগাভাগির মাধ্যমে অক্টেট গঠন।
• কোভ্যালেন্ট বন্ধন: ইলেকট্রনের শেয়ারিং এর মাধ্যমে গঠিত বন্ধন।

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২. রাসায়নিক বন্ধনের ধরণ

• আয়নিক বন্ধন: ইলেকট্রনের সম্পূর্ণ স্থানান্তরের মাধ্যমে ধনাত্মক ও ঋণাত্মক আয়নের মধ্যে তৈরি বন্ধন।
• কোভ্যালেন্ট বন্ধন: ইলেকট্রনের শেয়ারিং এর মাধ্যমে তৈরি। এটি সিগমা (σ) এবং পাই (π) বন্ধন হতে পারে।

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৩. অণুর আকৃতি ও বন্ধনের বৈশিষ্ট্য

• VSEPR তত্ত্ব: পরমাণুর ভ্যালেন্স শেলে ইলেকট্রন জোড়ের মধ্যে পারস্পরিক বিকর্ষণ অণুর আকৃতি নির্ধারণ করে।
• বন্ধনের দৈর্ঘ্য ও কোণ: বন্ধন দৈর্ঘ্য হলো দুটি বন্ধনযুক্ত পরমাণুর কেন্দ্রের মধ্যে দূরত্ব। বন্ধন কোণ ইলেকট্রন জোড়ের বিন্যাস নির্ধারণ করে।
• ডিপোল মোমেন্ট: বন্ধনের মেরুকরণ পরিমাপ করার উপায়।

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৪. ভ্যালেন্স বন্ড তত্ত্ব

• অরবিটাল ওভারল্যাপ ধারণা: পরমাণুর ভ্যালেন্স অরবিটালগুলি একে অপরের সাথে ওভারল্যাপ করে বন্ধন গঠন করে।
• অরবিটালের সংমিশ্রণ: হাইব্রিডাইজেশনের মাধ্যমে নতুন অরবিটাল তৈরি হয় যা বন্ধনের আকৃতি এবং দিকনির্দেশনা নির্ধারণ করে।

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৫. অণুর অস্বাভাবিক গঠন ও সীমাবদ্ধতা

• অক্টেট নিয়মের ব্যতিক্রম: অসম্পূর্ণ অক্টেট, বর্ধিত অক্টেট এবং বিজোড় ইলেকট্রন বিশিষ্ট অণু।
• রেজোনেন্স: একাধিক লুইস স্ট্রাকচার ব্যবহার করে অণুর প্রকৃত গঠন নির্ধারণ।

MCQs for NEET, JEE, IIT, NIT, CUET, CTET, and SSC Entrance Exams: Your Ultimate Preparation Guide

Are you preparing for competitive exams like NEET, JEE, IIT, NIT, CUET, CTET, or SSC? Multiple Choice Questions (MCQs) are a proven way to enhance your preparation strategy. These MCQs are designed to strengthen your concepts, boost problem-solving skills, and improve time management—key elements to ace any entrance exam.

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Exams These MCQs Help With:

• NEET: For aspiring medical students.
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1. Regular Practice: Dedicate time daily to solve topic-wise MCQs.
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