Textbook Question
The diagram to the right shows plots of vapor pressure versus temperature for a solvent and a solution.
b. What is the approximate boiling-point elevation for the solution?
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Ch.9 Solutions
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
Chapter 9, Problem 22c
The diagram to the right shows plots of vapor pressure versus temperature for a solvent and a solution.
c. What is the approximate concentration of the solution in mol/kg, if 1 mol of solute particles raises the boiling point of 1 kg of solvent by 3.63 °C?
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Verified step by step guidance1
Step 1: Analyze the graph provided. The blue curve represents the vapor pressure of the pure solvent, while the orange curve represents the vapor pressure of the solution. The boiling point is determined by the temperature at which the vapor pressure equals 760 mmHg (the dashed horizontal line). Identify the boiling points for both the solvent and the solution from the graph.
Step 2: Calculate the boiling point elevation (ΔT_b) by subtracting the boiling point of the pure solvent from the boiling point of the solution. This value represents the increase in boiling point due to the presence of solute particles.
Step 3: Use the boiling point elevation formula: ΔT_b = i × K_b × m, where ΔT_b is the boiling point elevation, i is the van't Hoff factor (number of particles the solute dissociates into), K_b is the boiling point elevation constant (given as 3.63 °C·kg/mol), and m is the molality (mol/kg). Rearrange the formula to solve for molality (m): m = ΔT_b / (i × K_b).
Step 4: Assume the solute does not dissociate (i = 1) unless otherwise specified. Substitute the values for ΔT_b (calculated in Step 2) and K_b (3.63 °C·kg/mol) into the formula to calculate the molality of the solution.
Step 5: Interpret the calculated molality (m) as the concentration of the solution in mol/kg. This value represents the approximate concentration of solute particles in the solution.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Vapor Pressure
Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. It indicates how readily a substance will evaporate; higher vapor pressure means a higher tendency to vaporize. In the context of the diagram, the vapor pressure of the solvent and solution changes with temperature, affecting boiling point elevation.
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Pressure Units Concept 1
Boiling Point Elevation
Boiling point elevation is a colligative property that describes how the boiling point of a solvent increases when a solute is added. This phenomenon occurs because the presence of solute particles disrupts the solvent's ability to vaporize, requiring a higher temperature to reach the boiling point. The relationship can be quantified using the formula ΔT_b = i * K_b * m, where ΔT_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.
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Molality
Molality is a measure of concentration defined as the number of moles of solute per kilogram of solvent. It is expressed in mol/kg and is particularly useful in colligative property calculations, such as boiling point elevation. In this question, determining the molality of the solution is essential to find out how much the boiling point has increased due to the addition of solute particles.
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Related Practice
Textbook Question
What is the osmolarity of the following solutions?
a. 0.35 M KBr
b. 0.15 M glucose + 0.05 M K2SO4
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Textbook Question
A typical oral rehydration solution (ORS) for infants contains 90 mEq/L Na+, 20 mEq/L K+, 110 mEq/L Cl– and 2.0% (m/v) glucose (MW = 180g/mol).
b. What is the osmolarity of the solution, and how does it compare with the osmolarity of blood plasma?
Textbook Question
When 1.0 mol of HF is dissolved in 1.0 kg of water, the boiling point of the resulting solution is 100.5 °C. Is HF a strong or weak electrolyte? Explain.
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Textbook Question
A typical oral rehydration solution (ORS) for infants contains 90 mEq/L Na+ , 20 mEq/L K+ , 110 mEq/L Cl- , and 2.0% (m/v) glucose (MW = 180g/mol)
a. Calculate the concentration of each ORS component in units of molarity.
Textbook Question
The typical concentration of Mg2+ in blood is 3 mEq/L. How many milligrams of Mg2+ are in 250 mL of blood?