Non‑aqueous solvents, molten salts, ionic liquids and supercritical fluids - Question Bank

1. When comparing supercritical fluids to their gaseous state at the same temperature, supercritical fluids generally have:
A) Lower density
B) Higher viscosity
C) Higher solvating power
D) Lower diffusion rates
2. The term 'ionic liquid' refers to a substance that is liquid below 100°C and consists entirely of:
A) Neutral molecules
B) Covalent compounds
C) Ions
D) Atoms
3. Which factor is LEAST important in classifying non-aqueous solvents?
A) Protic or aprotic nature
B) Polarity
C) Chemical reactivity
D) Viscosity
4. Supercritical water can be used for:
A) Dry cleaning
B) Decaffeination of coffee
C) Waste treatment and oxidation
D) Extraction of essential oils
5. Which property of ionic liquids allows them to dissolve a wide range of organic and inorganic compounds?
A) High viscosity
B) Low polarity
C) Tunable solvating power
D) Inertness
6. The use of molten salts in nuclear reactors is primarily for:
A) Coolant and fuel carrier
B) Moderating neutron speed
C) Shielding radiation
D) Controlling fission rate
7. Which of the following is a disadvantage of using protogenic solvents?
A) They can cause degradation of acid-sensitive compounds
B) They have very low dielectric constants
C) They do not readily donate protons
D) They are highly volatile
8. Aprotic polar solvents are characterized by:
A) High dielectric constants and the ability to form hydrogen bonds
B) Low dielectric constants and the absence of hydrogen bonding
C) High dielectric constants and the absence of hydrogen bonding
D) Low dielectric constants and the ability to form hydrogen bonds
9. Which property of molten salts makes them suitable for high-temperature reactions?
A) Low boiling point
B) High vapor pressure
C) High thermal stability
D) Low melting point
10. Supercritical fluid chromatography (SFC) uses a supercritical fluid as the mobile phase. This offers advantages such as:
A) High viscosity
B) Low diffusion coefficients
C) Fast separation speeds
D) Limited range of compounds that can be separated
11. The 'green' aspect of ionic liquids is primarily due to their:
A) Biodegradability
B) Low toxicity
C) Negligible vapor pressure
D) Renewable sources
12. Ionic liquids can be synthesized from a combination of:
A) A weak acid and a weak base
B) A strong acid and a strong base
C) An organic cation and an inorganic anion
D) An organic cation and an organic anion
13. Which solvent system is often used for dissolving metal oxides?
A) Liquid ammonia
B) Molten salts
C) Supercritical CO2
D) Aprotic organic solvents
14. Consider the autoionization of a solvent: 2SH <=> SH2+ + S-. The solvent is:
A) Protogenic
B) Protophilic
C) Aprotic
D) Amphiprotic
15. The ability of a solvent to undergo autoionization is important for:
A) Increasing its viscosity
B) Determining its dielectric constant
C) Its behavior in acid-base chemistry
D) Reducing its vapor pressure
16. Which of the following is a good example of an amphiprotic solvent?
A) Methanol
B) Ethanol
C) Sulfuric acid
D) All of the above
17. Amphiprotic solvents are those that:
A) Only donate protons
B) Only accept protons
C) Can both donate and accept protons
D) Cannot donate or accept protons
18. Which of the following is a disadvantage of using supercritical fluids?
A) High operating pressures required
B) Low solubility of most compounds
C) Limited tunability of solvent properties
D) Inability to dissolve non-polar compounds
19. The critical point of a substance is:
A) The temperature at which it boils at 1 atm
B) The pressure at which it freezes
C) The unique temperature and pressure above which it cannot be liquefied
D) The temperature at which it sublimes
20. Which property of supercritical fluids allows for easy separation from extracted solutes?
A) High viscosity
B) Low diffusion rate
C) Reducing pressure to gas phase
D) Inability to dissolve anything
21. Which of the following is NOT a typical application of supercritical fluids?
A) Extraction of natural products
B) Chemical synthesis
C) Drying of sensitive materials
D) Use as a lubricant in high-temperature engines
22. Supercritical fluids exhibit properties intermediate between:
A) Solids and liquids
B) Liquids and gases
C) Gases and plasma
D) Solids and gases
23. The solvating power of a supercritical fluid can be altered by changing:
A) Its chemical formula
B) The ambient temperature
C) Pressure and temperature
D) Its color
24. Supercritical carbon dioxide (scCO2) is often favored for extraction processes due to its:
A) High flammability
B) Low toxicity and non-flammability
C) High polarity
D) Low solvating power
25. What is the most common supercritical fluid used in industrial applications?
A) Supercritical water
B) Supercritical carbon dioxide
C) Supercritical ammonia
D) Supercritical methane
26. Supercritical fluids are substances that exist at a temperature and pressure above their:
A) Boiling point
B) Melting point
C) Triple point
D) Critical point
27. Which property makes ionic liquids suitable for use as electrolytes?
A) Poor electrical conductivity
B) High viscosity
C) Good ionic conductivity
D) Low thermal stability
28. The tunability of ionic liquids refers to their ability to:
A) Change color with temperature
B) Be synthesized with specific properties
C) Evaporate at room temperature
D) React with atmospheric oxygen
29. Anions commonly found in ionic liquids include:
A) Sulfate (SO4^2-)
B) Phosphate (PO4^3-)
C) Hexafluorophosphate ([PF6]-)
D) Nitrate (NO3-)
30. Which of the following is a typical cation found in ionic liquids?
A) Sodium ion (Na+)
B) Potassium ion (K+)
C) Imidazolium ion
D) Chloride ion (Cl-)
31. What is a key characteristic of ionic liquids that makes them 'green' solvents?
A) High flammability
B) Low vapor pressure
C) Toxicity
D) High volatility
32. Ionic liquids (ILs) are defined as salts that are liquid at temperatures below:
A) 100°C
B) 50°C
C) 25°C
D) 0°C
33. The high temperatures required for molten salts can be a disadvantage due to:
A) Increased solvent evaporation
B) Material compatibility issues
C) Decreased reaction rates
D) Reduced solubility of reactants
34. Which molten salt system is widely studied for its use in solar thermal energy storage?
A) NaCl-KCl
B) NaNO3-KNO3
C) LiCl-KCl
D) CaCl2-NaCl
35. Molten salts typically exhibit:
A) Low electrical conductivity
B) High electrical conductivity
C) Non-ionic behavior
D) Poor thermal stability
36. Which of the following is a common application of molten salt solvents?
A) Organic synthesis requiring mild conditions
B) Electrochemistry and energy storage
C) Catalysis in aqueous systems
D) Chromatographic separations
37. What is a major advantage of using molten salts as solvents?
A) Low operating temperatures
B) High vapor pressure
C) Wide liquid range
D) Low conductivity
38. Molten salts are ionic compounds that are liquid at temperatures:
A) Below their melting point
B) At or above their melting point
C) Below room temperature
D) Above their boiling point
39. Which property of a solvent is crucial for its ability to dissolve ionic compounds?
A) Low viscosity
B) High dielectric constant
C) Low boiling point
D) High surface tension
40. Aprotic solvents lack:
A) Polarity
B) Hydrogen bonding capability
C) Ability to dissolve ionic compounds
D) Chemical reactivity
41. Which of the following solvents is considered aprotic?
A) Sulfuric acid
B) Formic acid
C) Dimethylformamide (DMF)
D) Hydrofluoric acid
42. Water is an example of which type of non-aqueous solvent?
A) Protogenic
B) Protophilic
C) Aprotic
D) Amphiprotic
43. Which solvent class can both donate and accept protons?
A) Protogenic
B) Protophilic
C) Aprotic
D) Amphiprotic
44. Liquid ammonia (NH3) is an example of which type of non-aqueous solvent?
A) Protogenic
B) Protophilic
C) Aprotic
D) Amphiprotic
45. Protophilic solvents are characterized by their ability to:
A) Donate protons
B) Accept protons
C) Neither donate nor accept protons
D) Both donate and accept protons
46. Which of the following is an example of a protogenic solvent?
A) Liquid ammonia
B) Acetic acid
C) Dimethyl sulfoxide
D) Benzene
47. Which type of non-aqueous solvent is characterized by its ability to accept protons?
A) Protogenic solvents
B) Protophilic solvents
C) Aprotic solvents
D) Amphiprotic solvents
48. What is the primary reason for using non-aqueous solvents in chemical reactions?
A) To increase reaction rate by increasing temperature
B) To achieve solubility of specific reactants or products
C) To provide a more environmentally friendly reaction medium
D) To simplify product isolation and purification
49. Which of the following is NOT a characteristic of a non-aqueous solvent?
A) Does not contain water
B) Can act as a proton donor or acceptor
C) Often exhibits a high dielectric constant
D) Used when water interferes with a reaction
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