Vapor Pressure and Boiling

Key Questions

• What is vapor pressure?

  Answer:

  The equilibrium vapour pressure is typically the pressure exerted by a liquid .... it is A FUNCTION of temperature...

  Explanation:

  By way of example, chemists and physicists habitually use #P_"saturated vapour pressure"#...where #P_"SVP"# is the vapour pressure exerted by liquid water. At #100# #""^@C#, #P_"SVP"=1*atm#. Why?

  Well, because this is the normal boiling point of water: i.e. the conditions of pressure (i.e. here #1*atm#) and temperature, here #100# #""^@C#, at which the VAPOUR PRESSURE of the liquid is ONE ATMOSPHERE...and bubbles of vapour form directly in the liquid. As an undergraduate you should commit this definition, or your text definition, to memory...

  At lower temperatures, water exerts a much lower vapour pressure...but these should often be used in calculations...especially when a gas is collected by water displacement. Tables of #"saturated vapour pressure"# are available.

  anor277 · 3 · Jun 21 2018

• How are vapor pressure and boiling point related?
• How do you find vapor pressure given boiling point and heat of vaporization?
• How do atmospheric pressure and elevation affect boiling point?
• Why is vapor pressure reduced in a solution?
• Why is vapor pressure lowering a colligative property?
• Why does vapor pressure increase with temperature?
• Why is vapor pressure independent of volume?
• What is the boiling point of milk?
• Why does vapor pressure decrease when a solute is added?
• How is the boiling point relate to vapor pressure?
• How does vapor pressure relate to intermolecular forces?
• How does vapor pressure relate to the boiling point?
• How does vapor pressure affect the volume?
• How does the boiling point change across the periodic table?
• How does the boiling point affect polarity?
• How do intermolecular forces affect the boiling point?
• How does the boiling point affect evaporation?
• How does the boiling point affect gas chromatography?
• How do you calculate the vapor pressure of ethanol?
• How do you calculate the vapor pressure of a solution?
• How do you calculate the boiling point of a solution?
• How do I calculate vapor pressure of water?
• How do boiling points relate to polar bonds?
• How do boiling points change at high altitudes?
• How can vapor pressure be lowered?
• How can boiling points be determined?
• How can boiling points be changed?
• Is boiling point a cooling process?
• What are some common mistakes students make with vapor pressure?
• What are some examples of vapor pressure?
• What is vapor pressure?
• Question #d5d1d
• Question #671ba
• Question #04e6f
• Question #385d0
• Question #a036b
• Question #50327
• Question #2bedc
• Question #ff3bb
• Question #e3d6d
• Question #3b50b
• What is the enthalpy of vaporization for a compound that has a vapor pressure of #"135 torr"# at #52^@ "C"# and #"24.3 torr"# at #0^@ "C"#?
• Question #66c6e
• Question #054d9
• Question #431cd
• Question #ea892
• When chlorobenzene is steam distilled at 100kPa,the boiling point of the mixture is 91°C. At this temperature,the vapor pressure of chlorobenzene is 29kPa.What is the mass of the distillate that contains 100g of chlorobenzene?
• When compound Q with a relative molecular mass of 120 is steam distilled,the mixture boils at 98°C. The vapor pressure of water is 94300Nm^-2 at this temperature. It the atm pressure is 100900Nm^-2,calculate the composition by mass of the distillate?
• How does intermolecular force vary with the size of the molecule?
• What causes vapor pressure?
• How would you rank the following compounds from highest to lowest vapor pressure: CH3CH2CH2OH, CH3OH, CH4, and CH3CH2OH?
• What occurs when the vapor pressure of a liquid is equal to the atmospheric pressure?
• What factors affect the vapor pressure of a liquid?
• What happens to the vapor pressure as the surface area of a liquid decreases?
• Does atmospheric pressure affect the vapor pressure of a liquid?
• The vapor pressure of dichloromethane, #"CH"_2"Cl"_2# at #0^@"C"# is 134 mmHg. The normal boiling point of dichloromethane is #40^@"C"#. How would you calculate its molar heat of vaporization?
• What is the vapor pressure of water at 100 degrees Celsius?
• A 2.01-L sample of O2(g) was collected over water at a total pressure of 785 torr and 25°C. When the O2(g) was dried (water vapor removed), the gas has a volume of 1.92 L at 25°C and 785 torr. How would you calculate the vapor pressure of water at 25°C?
• Why does the temperature of a substance increase as vapor pressure increases?
• As the temperature of a liquid increases, what happens to its vapor pressure?
• At 20°C the vapor pressure of benzene (C6H6) is 75 torr, and that of toluene (C7H8) is 22 torr. Assume that benzene and toluene form an ideal solution. What is the composition in mole fractions of a solution that has a vapor pressure of 40. torr at 20°C?
• When does vaporization take place?
• What is the relationship between the #"normal boiling point"# and #"atmospheric pressure"#?
• When three phases are in equilibrium, what is it called?
• What is the #"flash point"#?
• What causes water's low vapor pressure?
• What is the difference in the boiling points of #O_2# and #O_3# at standard pressure in terms of intermolecular forces?
• Why does water have an unusually low vapor pressure for a liquid?
• Question #d29a9
• Why do boiling points differ between materials?
• Why is the vapour pressure of a boiling liquid the same as the ambient pressure?
• What is the ester formed by #"acetic acid"# and #"n-butanol"#?
• Which solution has the higher vapor pressure? #(A)# A solution that boils at #100^@ "C"# #(B)# A solution that boils at #-33^@ "C"#
• How are the volatilities of the Group 16, and Group 17 hydrides rationalized?
• Question #7bb22
• Question #2438c
• Question #877df
• What would happen to the boiling point of a substance if the elevation were to rise?
• Question #da0c9
• How do you calculate boiling point?
• How do you calculate boiling point at different pressures?
• How do you calculate boiling point of a solution?
• How do you calculate the boiling point of a compound?
• How do you calculate the boiling point of a substance?
• How do you calculate boiling point change?
• How do you calculate boiling point of a mixture?
• How do you calculate boiling point of water at different pressures?
• How do you find vapor pressure?
• How do you find vapor pressure of water?
• If given a boiling point, how do you find vapor pressure?
• How can you find the vapor pressure of a liquid?
• How do you find vapor pressure of water at given temperature?
• Equal quantities of different liquids are placed in closed manometers at 20°C. Which liquid has the highest vapor pressure?
• Question #4402a
• How does the boiling point of a liquid evolve if a non-volatile solute is added?
• What is the boiling point of methanol at 25 mmHg if its normal boiling point is 64.70 °C and #Δ_text(vap)H = "35.21 kJ·mol"^"-1"#?
• How do you calculate the vapor pressure of water above a solution prepared by adding 22.5 g of lactose [#C_12H_22O_11# ]tp 200 grams of water at 338 K?
• A solution of sodium chloride in water has a vapor pressure of 19.6 torr at 25 degrees Celsius. What is the mole fraction of NaCl solute particles in this solution?
• How do you calculate the vapor pressure of water above a solution prepared by dissolving 39.5 g in glycerin (#C_3H_8O_3#) to 149 g of water at 343 K?
• What is water vapor pressure at 90 degrees Celsius?
• The vapor pressure of water at 20 C is 17.5mmHg. What is the vapor pressure of water over a solution prepared from 200g of sucrose (#C_12H_22O_11#) and 112.3 g of water?
• What distinguishes #HF#, #H_2O#, and #CH_4# in terms of intermolecular force?
• Air at 30 degrees Fahrenheit is saturated when it has 20 g/kg water vapor. What is the relative humidity when the air is at 10 g/kg of water vapor?
• Suppose 0.50 g of pure water is sealed in an evacuated 5.0-L flask and the whole assembly is heated to 60 degrees C. Will any liquid water be left in the flask or does all of the water evaporate?
• How would the vapor pressure of a solution that contains .5 mol of #CaCl_2# in 1.0 kg of water compare with the vapor pressure of a solution that contains 1.5 mol of glucose in 1.0 kg of water?
• Would the boiling point of water be higher or lower on the top of a mountain peak? How would the boiling point be affected in a pressurized boiler system?
• What is the boiling point of a 0.321m aqueous solution of #NaCl#?
• What is the boiling point of a 0.527 m aqueous solution of LiBr?
• Question #186e8
• From the series, #"butane"#; #"methylbutane"#; #"neopentane"#; #"pentane"#, why does pentane have the highest boiling point?
• Question #b39e8
• How does boiling point evolve with decreasing pressure?
• Question #4e240
• What is #"steam distillation"#?
• At what temperature would 250 mL water boil? 1000 mL? Is the boiling point an intensive or extensive property?
• How does boiling point depend on pressure and temperature?
• Why is the boiling point of #NH_3# higher than the boiling point of #PH_3# and #AsH_3#?
• What is #"steam-distillation"#?
• Question #b3399
• How is the boiling point of water altered at pressure LESS than #1*atm#?
• #ICl# has a higher boiling point than #Br_2#. What is the best explanation for this?
• What will increasing the amount of liquid in a closed container cause the vapor pressure of the liquid to do?
• What is the direct vaporization of a solid without passing through its liquid state called?
• Is it true that the stronger the intermolecular interactions the higher the vapor pressure?
• Increasing the total pressure above a liquid will cause the boiling point of the liquid to do what?
• A sample of ethanoic acid is at 85°C. At a pressure of 50 kPa, what increase in temperature is needed to reach the boiling point of ethanoic acid?
• How do you determine highest boiling point?
• Given the following, what is the pressure of dry hydrogen gas if the vapor pressure of water at 25°C is 3.8 mm Hg?
• Question #b9d73
• Why does boiling water in a pot on a stove have a temperature of 100°C even if it has been boiling an hour?
• What would happen to the boiling point of water at 8,000 m above sea level, where air pressure is lower?
• Would water occur as a gas on the moon, because there is a vacuum?
• Why is it incorrect to say that the boiling point of a substance is 100 C?
• On a mountaintop, it is observed that water boils at 90°C, not at 100°C as at sea level. Why does this phenomenon occur on the mountaintop?
• The vapor pressure of ethanol is 100 mmHg at 34.9°C. What is its vapor pressure at 55.5°C?
• The Henry's law constant for methylamine (#CH_3NH_2#) is 36M/bar. What is the equilibrium vapor pressure of methylamine over a solution that is 2.23 mM #CH_3NH_2#?
• If a liquid exerts a vapour pressure at a given temperature is it boiling?
• Question #c71ad
• Question #4310f
• What is the vapor pressure of water at 105°C?
• Which of the following best represents the molecules in a pot of boiling water?
• How would you predict the boiling point of a 0.200 m solution of potassium iodide in water?
• In terms of intermolecular forces, what are the difference in the boiling points of #O_2# and #O_3# at standard pressure?
• At standard pressure, #CH_4# boils at 112 K and #H_2O# boils at 373 K. What accounts for the higher boiling point of #H_2O# at standard pressure?
• The value of #DeltaH_(vap)# of substance X is 45.7 kJ/mol and its normal boiling point is 72.5 degrees C. How do you calculate #DeltaS_(vap)#, #DeltaS_(surr)# and #DeltaG_(vap)# for the vaporization of one mole of this substance at 72.5°C and 1 atm?
• What is the new boiling temperature for bromine, if the pressure changes from atmospheric pressure to #"76000 Pa"#?
• What is the new vapor pressure for water that now boils at #90^@ "C"# instead of #100^@ "C"#?
• How do you determine which of a group of molecules has the highest boiling point?
• Question #b7786
• Octane has a molar mass of 114 grams per mole. What is the boiling point of octane at standard pressure?
• In what state is ethanol at #25# #""^@C#, and #1*atm#?
• For the hydrogen halide series, #HBr, HI, HCl, HF# can you give the order of boiling points?
• What is the boiling point of #"octocrylene"#?
• Question #ea75e
• Question #8d65e
• Question #7551d
• Of the given the following solvents, which should give rise to the greatest vapour pressure at laboratory temperature?
• What is the mol fraction of benzene in the vapour phase if equal mols of benzene and toluene are dissolved in the same solution? The pure vapor pressures of benzene and toluene are #"22 torr"# and #"75 torr"# respectively, at this temperature.
• Given acids, alkanes, alkyl halides, amines, and alcohols, of comparable molecular mass, what is the probably order of volatility?
• What is the pressure when a liquid is boiling at its normal boilinq point?
• What are bubbles in boiling water made of?
• If the normal boiling point of acetone is #56^@ "C"# and it has a #DeltaH_(vap)^@# of #"32.1 kJ/mol"#, estimate the boiling point at #"5 bar"#?
• When a system has constant vapor pressure, what exists between the liquid and its vapor?
• Question #d570d
• Acetic acid has a boiling point of 118.5 deg C and a #K_b# of 3.08 C/m. What is the boiling point of a 3.20 m solution of #Ca(NO_3)_2# in acetic acid?
• Acetic acid has a boiling point of #118.5^@ "C"# and a #K_b# of #3.08^@ "C/m"#. What is the boiling point of a #"3.20 m"# solution of #Ca(NO_3)_2# in acetic acid?
• What is the normal boiling point of a liquid defined as?
• What is the relationship between boiling point and pressure?
• Is the bubbling of a liquid caused by the rapid escape of a gas rather than by boiling?
• What term describes the rising of cold water from deeper layers to replace warmer surface water?
• How do the chemical potentials compare for the vapour and liquid phases at, below, and above the boiling point in a phase diagram?
• If you heat a liquid and measure its boiling point, what are you measuring?
• What is the boiling point of a solution that contains 3 moles of #KBr# in 2000 g of water? (#K_b# = 0.512 C/m; molar mass of water = 18 g)?
• What is the boiling point of #CO_2#?
• How do you find the boiling point of #O_2#?
• Why isn't the volume decreasing?
• Why does antifreeze also raise the boiling point of water?
• Question #af560
• What is the vapor pressure of a liquid at its normal boiling temperature?
• How many grams of fluorine gas will exert a pressure of 1.54 atm in a 3.2-liter container at 40 °C?
• How many kilojoules of heat are required to vaporize 50.0 g of ethanol, #C_2H_6O#? The boiling point of ethanol is 78.3°C. Its molar heat of vaporization is 38.6 kJ/mol.
• What is the temperature difference between a solution's boiling point and a pure solvent's boiling point called?
• How do you calculate the freezing point and the boiling point of the solution formed when 0.150 g of glycerol (#C_3H_8O_3#) is added to 20.0 g of water? #K_(er) (H_2O)# = 1.86°C, #K_b (H_2O)# = 0.52 C?
• Why does vinegar NOT have a constant boiling point?
• Question #31f33
• How does the boiling point of water change as altitude increases?
• When benzene vaporizes into a vacuum at #60^@ "C"# and #"1 atm"#, is it reversible or irreversible?
• Question #4d87c
• How does water boil in a pot without a lid?
• Account for the volatilities of #HF#, and #"carbon dioxide"#. Why should #CO_2# be MORE volatile than the lighter #HF# molecule?
• Which of the following can hydrogen-bond with itself?
• Does adding a nonvolatile solute to a liquid tend to increase or to decrease its vapor pressure?
• If benzene and toluene have pure vapor pressures of #"700 torr"# and #"600 torr"# respectively at a certain temperature, then upon mixing equal mols of both together, what is the mol fraction of benzene above the solution phase?
• How many mols are there of methanol and ethanol above the solution if the partial vapor pressures of methanol and ethanol are #"2.619 kPa"# and #"4.556 kPa"# respectively?
• When the nonvolatile solute #B# is added into volatile solvent #A# in a #2:5# mol ratio, the vapor pressure of #A# drops to #"250 torr"#. What will the vapor pressure of #A# above the solution be if #B# is added to #A# at a #3:5# mol ratio instead?
• How do we account for the volatility of the hydrogen halide series?
• What is boiling? When does a substance boil?
• What would happen to the boiling point if the atmospheric pressure would begin to rise?
• The vapor pressure of solid iodine at 25 °C is 42 mmHg. What is the vapor pressure in atm and torr?
• What can be said about the vapor pressure of a solution of 10g of sucrose in 100 g of water?
• How is vapor pressure related to decreasing boiling point and the ease of boiling?
• At pressures greater than 1 atm, what will water boil at?
• The liquid boils at 82°C. It is clear and colorless so it is suggested that it is just water. Do you think it might be?
• Question #b1bd7
• How is water vapour a component of air?
• If #"6.5 g"# of solute #X# is dissolved in #"50 g"# of ether solvent (#"74 g/mol"#) whose vapor pressure dropped from #"445 mm Hg"# to #"410 mm Hg"#, what is the molar mass of #X#?
• Question #13275
• Prove that the freezing point of water is 0 and the boiling point of water is 100?
• Do solids and liquids exert a vapour pressure?
• Given the enthalpy and entropy change of a natural phase transition, derive an expression for the normal boiling point of any substance? Hint: consider that the change in Gibbs' free energy is zero for two phases in equilibrium.
• How does boiling point relate to molecular mass?
• Question #e4ab2
• Is evaporation a good means of isolating a solid from a solution?
• When a certain amount of benzene and toluene are mixed, the total vapor pressure above the solution is #"760 torr"#. Assuming an ideal solution is formed, and knowing the pure vapor pressures, what is the mol fraction of benzene in the solution phase?
• What is the main difference between evaporation and vaporization?
• How do vapour pressures of substances like dry ice, and water, and mercury, relate to boiling point?
• Question #a9c80
• Question #07e2d
• How does the boiling point of water evolve with ambient pressure?
• How does pumice help while finding the boiling point of water?
• The vapor pressure of 10 mL of ethanol at 20°C is 5.85 kPa. What is the vapor pressure of 20 ml of ethanol at the same temperature?