14. Solutions

Vapor Pressure Lowering (Raoult's Law)

13.3 Vapor Pressure Depression and Raoult's Law

A solution contains a mixture of pentane and hexane at room 
temperature. The solution has a vapor pressure of 258 torr. 
Pure pentane and hexane have vapor pressures of 425 torr 
and 151 torr, respectively, at room temperature. What is the 
mole fraction composition of the mixture? (Assume ideal 
behavior.)

The vapor pressure of pure water at 60 °C is 149 torr. The 
vapor pressure of water over a solution at 60 °C containing 
equal numbers of moles of water and ethylene glycol (a 
nonvolatile solute) is 67 torr. Is the solution ideal according to Raoult’s law?

A solution of LiCl in a mixture of water and methanol 1CH3OH2 has a vapor pressure of 39.4 mm Hg at 17 °C and 68.2 mm Hg at 27 °C. The vapor pressure of pure water is 14.5 mm Hg at 17 °C and 26.8 mm Hg at 27 °C, and the vapor pressure of pure methanol is 82.5 mm Hg at 17 °C and 140.3 mm Hg at 27 °C. What is the composition of the solution in mass percent?

The vapor pressure of water at 100.0ºC is 0.720 atm. Determine the mass percent of iron (II) chloride, FeCl2, needed to reduce its vapor pressure to 0.655 atm. (MW of FeCl2 is 126.756 g/mol)

12. A solution contains 4.08 g of chloroform 1CHCl32 and 
9.29 g of acetone 1CH3COCH32. The vapor pressures at 35 
°C of pure chloroform and pure acetone are 295 torr and 332 torr, respectively. Assuming ideal behavior, calculate the vapor pressure above the solution. (LO 13.12) 
(a) 256 torr (b) 314 torr 
(c) 325 torr (d) 462 torr

At 60 °C, compound X has a vapor pressure of 96 mm Hg, benzene 1C6H62 has a vapor pressure of 395 mm Hg, and a 50:50 mixture by mass of benzene and X has a vapor pres- sure of 299 mm Hg. What is the molar mass of X?

Raoult's Law With Example Problem

A “canned heat” product used to warm buffet dishes consists of a homogeneous mixture of ethanol 1C2H5OH2 and
paraffin, which has an average formula of C24H50. What
mass of C2H5OH should be added to 620 kg of the paraffin
to produce 8 torr of ethanol vapor pressure at 35 °C? The
vapor pressure of pure ethanol at 35 °C is 100 torr.

At 63.5 °C, the vapor pressure of H2O is 175 torr, and that of
ethanol 1C2H5OH2 is 400 torr. A solution is made by mixing equal masses of H2O and C2H5OH. (a) What is the mole
fraction of ethanol in the solution?

Understanding Raoult's Law & Vapor Pressure Lowering

Vapor Pressure Lowering Concept 1

An aqueous CaCl2 solution has a vapor pressure of 81.6 mmHg
at 50 °C. The vapor pressure of pure water at this temperature is
92.6 mmHg. What is the concentration of CaCl2 in mass
percent? (Assume complete dissociation of the solute.)

What is the vapor pressure in mm Hg of the following solu-tions, each of which contains a nonvolatile solute? The vapor pressure of water at 45.0 °C is 71.93 mm Hg.
(b) A solution of 10.0 g of LiCl in 150.0 g of water at 45.0 °C, assuming complete dissociation

At 63.5 °C, the vapor pressure of H2O is 175 torr, and that of
ethanol 1C2H5OH2 is 400 torr. (b) Assuming idealsolution behavior, what is the vapor pressure of the solution at 63.5 °C?

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?

Bromine is sometimes used as a solution in tetrachloro- methane, CCl4. What is the vapor pressure in mm Hg of a solution of 1.50 g of Br2 in 145.0 g of CCl4 at 300 K? The vapor pressure of pure bromine at 300 K is 30.5 kPa, and the vapor pressure of CCl4 is 16.5 kPa.

Calculate the vapor pressure at 25 °C of an aqueous solution 
that is 5.50% NaCl by mass. (Assume complete dissociation of 
the solute.)

Vapor Pressure Lowering Example 1

A solution of a nonvolatile solute in water has a boiling point of 
375.3 K. Calculate the vapor pressure of water above this solution 
at 338 K. The vapor pressure of pure water at this temperature 
is 0.2467 atm.

The vapor pressure of carbon tetrachloride, CCl4, is 0.354 atm, and 
the vapor pressure of chloroform, CHCl3, is 0.526 atm at 316 K. A 
solution is prepared from equal masses of these two compounds at 
this temperature. Calculate the mole fraction of the chloroform in 
the vapor above the solution. If the vapor above the original solution 
is condensed and isolated into a separate flask, what will the 
vapor pressure of chloroform be above this new solution?

Determine the vapor pressure lowering associated with 1.32 m C6H12O6 solution (MW:180.156 g/mol) at 25°C. The vapor pressure of pure water at 25°C is 23.8 torr.

How many grams of glucose, C6H12O6, must be added to 515.0 g of water to give a solution with a vapor pressure of 13.2 torr at 20.0ºC? The vapor pressure of pure water at 20.0ºC is 17.5 torr.

13 - Solutions and Colligative Properties

At 20 °C, the vapor pressure of benzene 1C6H62 is 75 torr,
and that of toluene 1C7H82 is 22 torr. Assume that benzene and toluene form an ideal solution. (b) What is the mole fraction of benzene in the vapor above the solution described 
in part (a)?

Two beakers are placed in a sealed box at 25 °C. One beaker
contains 30.0 mL of a 0.050 M aqueous solution of a nonvolatile nonelectrolyte. The other beaker contains 30.0 mL
of a 0.035 M aqueous solution of NaCl. The water vapor
from the two solutions reaches equilibrium. (b) What are the volumes in the two beakers when
equilibrium is attained, assuming ideal behavior?

Calculate the vapor pressure of a solution containing 24.5 g of 
glycerin (C3H8O3) in 135 mL of water at 30.0 °C. The vapor pressure 
of pure water at this temperature is 31.8 torr. Assume that 
glycerin is not volatile and dissolves molecularly (i.e., it is not 
ionic), and use a density of 1.00 g>mL for the water.

The density of a 0.438 M solution of potassium chromate
(K2CrO4) at 298 K is 1.063 g>mL. Calculate the vapor pressure of
water above the solution. The vapor pressure of pure water at
this temperature is 0.0313 atm. (Assume complete dissociation
of the solute.)

42: Using Raoult's Law

Colligative Properties - Boiling Point Elevation, Freezing Point Depression & Osmotic Pressure

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[BOOK CHEM] Clutch Version

Types of Aqueous Solutions

When an ionic solid dissolves, ions leave the solid and become dispersed in the solvent. Three possible aqueous solutions can be formed:saturated, unsaturated and supersaturated.

Boiling Point Elevation

Boiling Point Elevation is the phenomenon when adding a solute to a pure solvent results in increased boiling point of the solvent.

Intro to Henry's Law

According to&nbsp;Henry's Law, at a constant temperature the amount of a gas dissolved in a solvent is directly proportional to its partial pressure when it is in equilibrium with its liquid phase.&nbsp;

Osmotic Pressure

Osmotic Pressure is the force that drives Osmosis from higher concentration to lower concentration.

Mole Fraction

Mole Fraction (X) relates the moles of solute and solvent within a solution.&nbsp;

The Colligative Properties

The&nbsp;Colligative Properties&nbsp;explain what happens to a pure solvent as it transitions to a solution.

Molality

Molality (m)&nbsp;represents the number of moles of solute dissolved per kilogram of solvent.&nbsp;

Freezing Point Depression

Freezing Point Depression is the phenomenon when adding a solute to a pure solvent results in decreased freezing point of the solvent.

Solutions: Solubility and Intermolecular Forces

Solutions are homogeneous mixtures that result from the dissolving of a solute by a solvent.

Vapor Pressure is the pressure exerted by a gas at equilibrium with its liquid phase at a specific temperature in a closed system.

Henry's Law Calculations

To calculate solubility of a dissolves gas, Henry's Law Constant and partial pressure are used.

Solutions: Mass Percent

Mass Percent represents grams of solute per grams of solution, multiplied by 100.

Osmosis

Osmosis is the net movement of solvent across a semipermeable membrane.

Parts per Million (ppm)

<div dir="auto"><div contenteditable="true"dir="auto"spellcheck="true">Parts per Million (ppm) and Parts per Billion (ppb) are used to express extremely dilute solution concentrations.</div></div>

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