Ch.12 - SolutionsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Problem

An aqueous CsCl solution is 8.00 wt% CsCl and has a density of 1.0643 g/mL at 20°C. What is the boiling point of this solution? Kb = 0.51°C/m for water. Enter your answer with 2 decimal places and no units.

a. 101.72°C

b. 100.30°C

c. 100.53°C

d. 103.91°C

e. 107.45°C


Solution

We’re being asked to calculate for the boiling point of an aqueous solution containing 8% (wt/wt) CsCl

Recall that the boiling point of a solution is higher than that of the pure solvent and the change in boiling point (ΔT­b) is given by:


ΔTb=ΔTb, solution-ΔTb, pure solvent



The change in boiling point is also related to the molality of the solution:


ΔTb=iKbm


where: 

i = van’t Hoff factor

m = molality of the solution (in m or mol/kg)

Kb = boiling point elevation constant (in ˚C/m)



We need to convert the 8% wt of CsCl to molality. Recall that the molality of a solution is given by:


Molality (m)=moles of soluteKilograms of solvent


We will calculate the boiling point of the solution using the following steps:

Step 1. Determine the composition of the solution.
Step 2. Calculate the moles of the solute.
Step 3. Calculate the mass of the solvent (in kg).
Step 4. Calculate the molality of the solution.
Step 5. Calculate the boiling point of the solution


Step 1. Determine the composition of the solution.

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