Exam 11: Solutions: Properties and Behavior

The molal concentration of ions in seawater is 1.17 m, and the molar concentration is 1.15 M. What is the minimum pressure that must be applied to produce pure water from seawater through reverse osmosis at 25°C?

Which of the following is needed to calculate the lattice energy of an ionic compound?

A petroleum company separates benzene (78 g/mol) and n-octane (114 g/mol) by distillation. In one run, the starting solution was 15% benzene and 85% n-octane by mass at 25°C. In the liquid, the mole ratio of benzene to n-octane was ________, and in the vapor it was ________. The vapor pressures for benzene and n-octane at this temperature are 11 torr and 95 torr, respectively.

Indicate which aqueous solution has the lowest vapor pressure.

Ethylene glycol is used commonly as an antifreeze in automobile radiators. Automobile temperatures in the U.S. are commonly measured in degrees Fahrenheit. What is the freezing point in °F of a 50:50 mixture of ethylene glycol and water by volume? (C₂H₆O₂, 62.07 g/mol, 1.1132 g/mL, K_f = 3.35°F/m).

A solution is prepared by mixing 75 g of methanol (CH₃OH) with 25 g of ethanol (CH₃CH₂OH). Use the following data to determine the vapor pressure of this solution at 20°C. Substance Vapor Pressure at (torr) Methanol 92 Ethanol 45

A solution is prepared by adding 0.300 mol glucose, which is not volatile, to 4.50 mol water. What is the vapor pressure of this solution at 25°C given that the vapor pressure of pure water is 23)8 torr?

You like boiled eggs for breakfast, but they take too long to cook, and you are always late to your early morning class. Lucky you! You have learned that adding table salt, NaCl (58.4 g/mol, 2)16 g/cm³), to water (K_b = 0.52°C/m) increases the temperature at which it boils. You figure that you can cook eggs faster at a higher temperature in boiling salty water! What increase in the boiling point do you expect if you add 4 tablespoons (1 tbsp = 14.8 cm³) of salt to 16 oz of water (474 mL)?

Given the same number of moles of each of the following substances, which one would be most effective in melting ice on a sidewalk?

A mixture of salt and ice is used to chill the contents of old-fashioned, hand-operated ice cream makers. What is the melting point of a mixture of 1.00 lb of sodium chloride and 16.00 lb of ice if exactly half the ice melts? Assume ideal behavior and that all the sodium chloride dissolves in the melted ice water. K_f (water) = 1.86°C/m

What is the molarity of a sucrose (C₁₂H₂₂O₁₁) solution that produces an osmotic pressure of 2)65 atm at 25°C?

Coulomb's law states that the interaction energy between ions depends ________

Which statement regarding osmotic pressure is not correct? Osmotic pressure ________

Ethylene glycol is used in automobile radiators as an antifreeze. What will the freezing point of an antifreeze solution be if 2.5 L of ethylene glycol are mixed together with 2.5 L of water? The following information may be helpful to you. Ethylene glycol has a very low vapor pressure and is essentially nonvolatile. Molar mass of ethylene glycol =62.1 g/mol Van 't Hoff factor = 1 Density of ethylene glycol =1.11 g/mL Density of water=1.00 g/mL K_f for water =1.86°C kg/mol

A 75 mg sample of a natural product isolated from alfalfa hay was dissolved in water to make 100.0 mL of solution. The solution did not conduct electricity and had an osmotic pressure of 0.246 atm at 27°C. What is the molar mass of this compound?

A solution is prepared by mixing 50 g of methanol (CH₃OH) with 50 g of ethanol (CH₃CH₂OH). Use the following data to determine the vapor pressure of this solution at 20°C. Substance Vapor Pressure at (torr) Methanol 92 Ethanol 45

Use the following data to calculate the enthalpy change for the following reaction: 2()+(g) \rightarrow(s) Quantity Magnitude (/) Ionization energy of (g) 495 Electron affinity of (g) for 2 603 Vaporization energy of (s) 109 Bond energy of (g) 499 Lattice energy for (s) -2,477

Does the temperature of the vapors in a still head increase or decrease as a fractional distillation progresses? Explain.

Which of the following would be most effective in melting ice on a sidewalk?

Which one of the ionic compounds below would you expect to have the smallest (least negative) lattice energy?