71. In the Freundlich adsorption isotherm, what does the value of 1/n1/n between 0 and 1 represent?
- a) The process is endothermic.
- b) Adsorption is favored at high pressure.
- c) The adsorption is physisorption.
- d) The adsorption intensity.
Answer: d) The adsorption intensity
Explanation: In the Freundlich adsorption isotherm, the value of 1/n1/n provides a measure of the adsorption intensity. When 1/n1/n is between 0 and 1, adsorption is favorable.
72. Which one of the following statements is incorrect for chemisorption?
- a) It is highly specific.
- b) It involves weak forces.
- c) It forms a monolayer.
- d) It is irreversible.
Answer: b) It involves weak forces
Explanation: Chemisorption involves the formation of strong chemical bonds between the adsorbate and the adsorbent, not weak forces like in physisorption.
73. Which of the following gases will be adsorbed to the greatest extent on activated charcoal at 25°C?
- a) Nitrogen
- b) Oxygen
- c) Carbon dioxide
- d) Hydrogen
Answer: c) Carbon dioxide
Explanation: Carbon dioxide is adsorbed more readily than other gases like nitrogen, oxygen, or hydrogen due to its higher polarizability and greater tendency to interact with the surface of the adsorbent.
74. Which statement is incorrect for adsorption?
- a) Adsorption is an exothermic process.
- b) The extent of adsorption increases with increasing temperature for physisorption.
- c) The extent of adsorption increases with increasing pressure.
- d) Adsorption is spontaneous.
Answer: b) The extent of adsorption increases with increasing temperature for physisorption
Explanation: Physisorption decreases with increasing temperature because higher thermal energy counteracts the weak Van der Waals forces responsible for adsorption.
75. In the context of adsorption, what is an “adsorbate”?
- a) The substance onto which adsorption occurs
- b) The substance being adsorbed
- c) A catalyst used in adsorption
- d) The surface area of the adsorbent
Answer: b) The substance being adsorbed
Explanation: The adsorbate is the substance that is being adsorbed onto the surface of the adsorbent during the adsorption process.
76. The BET equation for adsorption is primarily used to determine:
- a) The volume of adsorbed gas
- b) The specific surface area of a solid
- c) The temperature of adsorption
- d) The thickness of the adsorbed layer
Answer: b) The specific surface area of a solid
Explanation: The BET equation is used to calculate the specific surface area of porous materials by analyzing multilayer adsorption data.
77. Which of the following is correct for the enthalpy change during chemisorption?
- a) It is positive.
- b) It is highly positive.
- c) It is negative.
- d) It is zero.
Answer: c) It is negative
Explanation: Chemisorption is an exothermic process, meaning the enthalpy change (ΔH) is negative as energy is released when chemical bonds are formed between the adsorbate and the adsorbent.
78. Which of the following can be used as an adsorbent for the removal of moisture from air?
- a) Activated charcoal
- b) Silica gel
- c) Fuller’s earth
- d) Graphite
Answer: b) Silica gel
Explanation: Silica gel is a commonly used desiccant that can efficiently adsorb moisture from the air due to its high surface area and porosity.
79. The adsorption of hydrogen on the surface of a transition metal like nickel at high temperature is an example of:
- a) Physisorption
- b) Chemisorption
- c) Both physisorption and chemisorption
- d) Multilayer adsorption
Answer: b) Chemisorption
Explanation: The adsorption of hydrogen on transition metals such as nickel at high temperatures involves chemical bond formation, which is characteristic of chemisorption.
80. In adsorption chromatography, the substance adsorbed is known as:
- a) Adsorbent
- b) Mobile phase
- c) Adsorbate
- d) Eluent
Answer: c) Adsorbate
Explanation: In adsorption chromatography, the substance that is adsorbed on the stationary phase is referred to as the adsorbate.
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