ICH 104 Past Questions and Answers

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1. In a reversible chemical reaction, the point at which the rate of the forward reaction equals the rate of the reverse reaction is called:
   A. Dynamic equilibrium
   B. Static equilibrium
   C. Rate constant
   D. Reaction quotient
   E. Le Chatelier’s principle
   Answer: A
2. Which of the following is NOT a characteristic of a reaction at equilibrium?
   A. The concentration of reactants and products remains constant
   B. The forward and reverse reactions stop
   C. The rates of the forward and reverse reactions are equal
   D. The system is closed
   E. The macroscopic properties remain unchanged
   Answer: B
3. What does the equilibrium constant (Kc) represent?
   A. The ratio of the forward and reverse reaction rates
   B. The ratio of product concentrations to reactant concentrations at equilibrium
   C. The temperature dependence of the reaction
   D. The energy change in the reaction
   E. The reaction mechanism
   Answer: B
4. Le Chatelier’s principle states that if a system at equilibrium is disturbed, it will shift to:
   A. Minimize the disturbance
   B. Increase the disturbance
   C. Stop the reaction
   D. Favor the side with more molecules
   E. Increase the reaction rate
   Answer: A
5. For the equilibrium reaction: N₂(g) + 3H₂(g) ⇌ 2NH₃(g), what happens when the pressure is increased?
   A. The reaction shifts to the right (towards NH₃)
   B. The reaction shifts to the left (towards N₂ and H₂)
   C. No change
   D. The reaction stops
   E. The reaction becomes faster
   Answer: A
6. If the concentration of a reactant is increased in a system at equilibrium, the system will:
   A. Shift to the left
   B. Shift to the right
   C. Remain unchanged
   D. Stop reacting
   E. Increase both forward and reverse reactions equally
   Answer: B
7. What effect does a catalyst have on a reaction at equilibrium?
   A. Shifts the equilibrium position
   B. Increases the equilibrium constant
   C. Speeds up both forward and reverse reactions
   D. Increases only the forward reaction
   E. Increases only the reverse reaction
   Answer: C
8. The value of the equilibrium constant (Kc) for a reaction changes with:
   A. Concentration
   B. Pressure
   C. Temperature
   D. Volume
   E. Catalyst
   Answer: C
9. For an exothermic reaction at equilibrium, increasing the temperature will:
   A. Shift the equilibrium to the right
   B. Shift the equilibrium to the left
   C. Have no effect on the equilibrium
   D. Stop the reaction
   E. Increase the value of the equilibrium constant
   Answer: B
10. Which of the following conditions will favor the production of ammonia in the Haber process (N₂ + 3H₂ ⇌ 2NH₃)?
    A. Low pressure, low temperature
    B. High pressure, low temperature
    C. Low pressure, high temperature
    D. High pressure, high temperature
    E. Low pressure, moderate temperature
    Answer: B
11. The study of the energy changes that accompany chemical and physical processes is called:
    A. Chemical kinetics
    B. Chemical thermodynamics
    C. Electrochemistry
    D. Quantum mechanics
    E. Photochemistry
    Answer: B
12. The first law of thermodynamics states that:
    A. Energy cannot be created or destroyed
    B. Entropy always increases
    C. The rate of reaction is proportional to the concentration of reactants
    D. Free energy is conserved
    E. The universe is expanding
    Answer: A
13. Which of the following is a state function in thermodynamics?
    A. Work
    B. Heat
    C. Enthalpy
    D. Reaction rate
    E. Activation energy
    Answer: C
14. In an exothermic reaction:
    A. Heat is absorbed from the surroundings
    B. Heat is released into the surroundings
    C. The reaction becomes cold
    D. There is no energy change
    E. The system loses pressure
    Answer: B
15. The entropy (S) of a system is a measure of:
    A. The heat content of the system
    B. The randomness or disorder in the system
    C. The work done by the system
    D. The temperature of the system
    E. The pressure of the system
    Answer: B
16. According to the second law of thermodynamics, spontaneous processes always result in:
    A. A decrease in entropy
    B. An increase in entropy
    C. Constant entropy
    D. An increase in enthalpy
    E. A decrease in temperature
    Answer: B
17. What is the standard Gibbs free energy change (ΔG°) at equilibrium?
    A. Positive
    B. Negative
    C. Zero
    D. Dependent on pressure
    E. Dependent on temperature
    Answer: C
18. The relationship between Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) is given by:
    A. ΔG = ΔH + TΔS
    B. ΔG = ΔH – TΔS
    C. ΔG = TΔS – ΔH
    D. ΔG = ΔH * TΔS
    E. ΔG = ΔS – ΔH
    Answer: B
19. A process is spontaneous at all temperatures when:
    A. ΔH > 0 and ΔS > 0
    B. ΔH < 0 and ΔS < 0 C. ΔH < 0 and ΔS > 0
    D. ΔH > 0 and ΔS < 0
    E. ΔH = 0 and ΔS = 0
    Answer: C
20. In an endothermic process, the system:
    A. Releases heat to the surroundings
    B. Absorbs heat from the surroundings
    C. Increases pressure
    D. Decreases entropy
    E. Does no work
    Answer: B

21. The change from solid to gas without passing through the liquid phase is called:
    A. Condensation
    B. Sublimation
    C. Melting
    D. Deposition
    E. Freezing
    Answer: B
22. At the melting point of a solid:
    A. The temperature increases
    B. The temperature decreases
    C. The temperature remains constant
    D. The pressure decreases
    E. The system becomes gaseous
    Answer: C
23. The temperature at which the vapor pressure of a liquid equals the external pressure is called:
    A. Freezing point
    B. Boiling point
    C. Melting point
    D. Condensation point
    E. Critical point
    Answer: B
24. What happens to the boiling point of water when atmospheric pressure decreases?
    A. Increases
    B. Decreases
    C. Remains the same
    D. Doubles
    E. Becomes negative
    Answer: B
25. The phase transition from gas to liquid is called:
    A. Freezing
    B. Melting
    C. Condensation
    D. Vaporization
    E. Deposition
    Answer: C
26. Which of the following processes is endothermic?
    A. Freezing of water
    B. Condensation of steam
    C. Melting of ice
    D. Deposition of gas
    E. Combustion of fuel
    Answer: C
27. The critical point is the temperature and pressure at which:
    A. A substance exists only as a gas
    B. A substance can exist as a solid, liquid, and gas
    C. A liquid becomes a solid
    D. The liquid and gas phases become indistinguishable
    E. The substance sublimes
    Answer: D
28. Which of these factors affects the vapor pressure of a liquid?
    A. Pressure
    B. Volume
    C. Surface area
    D. Temperature
    E. Mass
    Answer: D
29. The triple point of a substance is the temperature and pressure at which:
    A. The solid and liquid phases coexist
    B. The solid, liquid, and gas phases coexist
    C. The liquid and gas phases coexist
    D. The gas and solid phases coexist
    E. The gas phase is dominant
    Answer: B
30. When a substance undergoes deposition, it changes from:
    A. Solid to liquid
    B. Gas to liquid
    C. Liquid to gas
    D. Gas to solid
    E. Solid to gas
    Answer: D
31. What is the normal boiling point of water at sea level?
    A. 50°C
    B. 75°C
    C. 100°C
    D. 120°C
    E. 0°C
    Answer: C
32. During which phase change does a substance absorb energy?
    A. Freezing
    B. Condensation
    C. Deposition
    D. Vaporization
    E. Crystallization
    Answer: D
33. What happens to the kinetic energy of particles during melting?
    A. Increases
    B. Decreases
    C. Remains constant
    D. Is transferred to the surroundings
    E. Converts to potential energy
    Answer: A
34. A supercooled liquid is a liquid that:
    A. Has a temperature below its freezing point but remains liquid
    B. Is above its boiling point
    C. Is in equilibrium with its solid form
    D. Has evaporated completely
    E. Is in the critical phase
    Answer: A
35. In a phase diagram, the line separating the liquid and gas phases is called the:
    A. Freezing curve
    B. Sublimation curve
    C. Vaporization curve

D. Melting curve
E. Deposition curve
Answer: C

36. At the boiling point, a substance:
    A. Freezes
    B. Gains energy and changes from liquid to gas
    C. Loses energy and changes from gas to liquid
    D. Gains energy and changes from gas to liquid
    E. Loses energy and changes from liquid to solid
    Answer: B
37. The process of changing directly from a gas to a solid without passing through the liquid phase is known as:
    A. Sublimation
    B. Deposition
    C. Condensation
    D. Freezing
    E. Melting
    Answer: B
38. Which phase transition occurs when water vapor condenses on a cold surface?
    A. Sublimation
    B. Deposition
    C. Melting
    D. Condensation
    E. Evaporation
    Answer: D
39. A phase diagram provides information about:
    A. Energy levels of atoms
    B. The equilibrium between different phases of a substance
    C. The solubility of gases in liquids
    D. The boiling point of a solution
    E. The color of a substance
    Answer: B
40. What happens to the boiling point of water when salt is added?
    A. It increases
    B. It decreases
    C. It remains constant
    D. It becomes unpredictable
    E. It reaches absolute zero
    Answer: A
41. Which of the following is an exothermic phase transition?
    A. Melting
    B. Vaporization
    C. Sublimation
    D. Freezing
    E. Evaporation
    Answer: D
42. What is the effect of increasing temperature on the solubility of gases in liquids?
    A. Increases solubility
    B. Decreases solubility
    C. No effect
    D. Depends on the gas
    E. Solubility becomes infinite
    Answer: B
43. During the freezing process, the potential energy of the molecules:
    A. Increases
    B. Decreases
    C. Remains the same
    D. Converts to kinetic energy
    E. Converts to heat
    Answer: B
44. A heating curve shows the relationship between:
    A. Heat added and temperature during phase changes
    B. Pressure and temperature at constant volume
    C. Volume and pressure during heating
    D. Mass and heat capacity
    E. Time and rate of reaction
    Answer: A
45. What happens to the entropy of a system during the melting of ice?
    A. Decreases
    B. Increases
    C. Remains the same
    D. Becomes zero
    E. Converts to enthalpy
    Answer: B
46. Which of the following processes does NOT involve a phase change?
    A. Boiling
    B. Freezing
    C. Dissolving
    D. Sublimation
    E. Melting
    Answer: C
47. The enthalpy change when one mole of a substance changes from liquid to gas at constant pressure is called:
    A. Heat of fusion
    B. Heat of vaporization
    C. Heat of combustion
    D. Heat of formation
    E. Heat capacity
    Answer: B
48. In a closed system, when the rate of evaporation equals the rate of condensation, the system has reached:
    A. Chemical equilibrium
    B. Phase equilibrium
    C. Static equilibrium
    D. Thermal equilibrium
    E. Dynamic equilibrium
    Answer: B
49. Which of the following does NOT affect the phase of a substance?
    A. Pressure
    B. Temperature
    C. Volume
    D. Concentration
    E. Intermolecular forces
    Answer: D
50. What is the relationship between vapor pressure and boiling point?
    A. When vapor pressure equals atmospheric pressure, the substance boils
    B. Vapor pressure is always lower than boiling point
    C. Vapor pressure and boiling point are inversely proportional
    D. Boiling point decreases as vapor pressure decreases
    E. Vapor pressure remains constant as boiling point changes
    Answer: A