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Vapor Pressure Lowering (Raoult's Law) quiz #1

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  • Which of the following substances would have the highest vapor pressure at 298 K: pure water, 1 M NaCl(aq), or 1 M glucose(aq)?
    Pure water would have the highest vapor pressure at 298 K because adding solute (NaCl or glucose) lowers the vapor pressure compared to the pure solvent.
  • Which of the following will increase the vapor pressure of a liquid: increasing temperature, adding a nonvolatile solute, or decreasing surface area?
    Increasing temperature will increase the vapor pressure of a liquid. Adding a nonvolatile solute lowers vapor pressure, and surface area does not affect vapor pressure in a closed system.
  • Which of the following aqueous solutions would have the highest vapor pressure: 1 M NaCl(aq), 1 M glucose(aq), or pure water?
    Pure water has the highest vapor pressure because the addition of any solute (NaCl or glucose) lowers the vapor pressure.
  • Which 1 M solution would have the highest vapor pressure at a given temperature: 1 M NaCl(aq), 1 M K2SO4(aq), or 1 M glucose(aq)?
    1 M glucose(aq) would have the highest vapor pressure because glucose does not dissociate, resulting in fewer particles and less vapor pressure lowering compared to ionic compounds like NaCl or K2SO4.
  • Which aqueous solution has the lowest vapor pressure: 1 M NaCl(aq), 1 M K2SO4(aq), or 1 M glucose(aq)?
    1 M K2SO4(aq) has the lowest vapor pressure because it dissociates into more ions, increasing the number of particles and lowering the vapor pressure more than NaCl or glucose.
  • A 0.100 m solution of which one of the following solutes will have the highest vapor pressure: NaCl, K2SO4, or urea?
    A 0.100 m solution of urea will have the highest vapor pressure because urea does not dissociate into ions, resulting in less vapor pressure lowering compared to NaCl or K2SO4.
  • Which of the following compounds has the highest vapor pressure at 25°C: ethanol, water, or glycerol?
    Ethanol has the highest vapor pressure at 25°C because it has weaker intermolecular forces compared to water and glycerol.
  • What is the pressure exerted by a vapor over a liquid in a closed system called?
    The pressure exerted by a vapor over a liquid in a closed system is called vapor pressure.
  • Which of the following pairs of substances has the higher vapor pressure at 298 K given first: pure water vs. 1 M NaCl(aq)?
    Pure water has the higher vapor pressure at 298 K compared to 1 M NaCl(aq).
  • What is ΔHvap for a particular organic compound if its vapor pressures at two temperatures are given?
    ΔHvap (enthalpy of vaporization) can be calculated using the Clausius-Clapeyron equation, which relates vapor pressures at two temperatures to ΔHvap.
  • Which of the following substances would you predict to have the highest ΔHvap: water, ethanol, or acetone?
    Water would have the highest ΔHvap because it has strong hydrogen bonding, requiring more energy to vaporize.
  • Which of the following statements are true about vapor pressure? Check all that apply: (a) Adding a nonvolatile solute lowers vapor pressure; (b) Vapor pressure increases with temperature; (c) Vapor pressure of a solution is always less than that of the pure solvent.
    All statements are true: (a) Adding a nonvolatile solute lowers vapor pressure; (b) Vapor pressure increases with temperature; (c) Vapor pressure of a solution is always less than that of the pure solvent.