Open Question
What is the vapor pressure in mm Hg of a solution of 16.0 g of glucose (C6H12O6) in 80.0 g of methanol (CH3OH) at 27 °C? The vapor pressure of pure methanol at 27 °C is 140 mm Hg.
Ch.13 - Solutions & Their Properties
Chapter 13, Problem 107
The van’t Hoff factor for KCl is i = 1.85. What is the boiling point of a 0.75 m solution of KCl in water? For water, Kb = 0.511°C kg/mol.
Verified step by step guidance1
Identify the formula for boiling point elevation: \( \Delta T_b = i \cdot K_b \cdot m \), where \( \Delta T_b \) is the boiling point elevation, \( i \) is the van’t Hoff factor, \( K_b \) is the ebullioscopic constant, and \( m \) is the molality of the solution.
Substitute the given values into the formula: \( i = 1.85 \), \( K_b = 0.511 \text{°C kg/mol} \), and \( m = 0.75 \text{ m} \).
Calculate \( \Delta T_b \) by multiplying the values: \( \Delta T_b = 1.85 \times 0.511 \times 0.75 \).
Determine the new boiling point of the solution by adding the boiling point elevation \( \Delta T_b \) to the normal boiling point of water, which is 100°C.
Conclude by stating that the boiling point of the solution is the sum of 100°C and \( \Delta T_b \).
Related Practice
Open Question
What is the freezing point in °C of each of the solutions in Problem 13.102? For water, Kf = 1.86 °C·kg/mol.
Open Question
A 1.0 m solution of K2SO4 in water has a freezing point of -4.3 °C. What is the value of the van’t Hoff factor i for K2SO4?
Open Question
Heptane (C₇H₁₆) and octane (C₈H₁₈) are constituents of gasoline. At 80.0 °C, the vapor pressure of heptane is 428 mm Hg, and the vapor pressure of octane is 175 mm Hg. What is the mole fraction of heptane (Xheptane) in a mixture of heptane and octane that has a vapor pressure of 305 mm Hg at 80.0 °C?
Textbook Question
Cyclopentane 1C5H102 and cyclohexane 1C6H122 are vola- tile, nonpolar hydrocarbons. At 30.0 °C, the vapor pres- sure of cyclopentane is 385 mm Hg, and the vapor pressure of cyclohexane is 122 mm Hg. What is Xpentane in a mixture of C5H10 and C6H12 that has a vapor pressure of 212 mm Hg at 30.0 °C?
332
views
Open Question
The industrial solvents chloroform (CHCl₃) and dichloromethane (CH₂Cl₂) are prepared commercially by the reaction of methane with chlorine, followed by fractional distillation of the product mixture. At 25 °C, the vapor pressure of CHCl₃ is 205 mm Hg, and the vapor pressure of CH₂Cl₂ is 415 mm Hg. What is the vapor pressure in mm Hg at 25 °C of a mixture of 15.0 g of CHCl₃ and 37.5 g of CH₂Cl₂?