Textbook Question
The density of acetonitrile (CH3CN) is 0.786 g/mL and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by dissolving 22.5 mL of CH3OH in 98.7 mL of CH3CN. (b) What is the molality of the solution?
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Ch.13 - Properties of Solutions
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970
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Table of contents
- Ch.1 - Introduction: Matter, Energy, and Measurement111
- Ch.2 - Atoms, Molecules, and Ions166
- Ch.3 - Chemical Reactions and Reaction Stoichiometry138
- Ch.4 - Reactions in Aqueous Solution127
- Ch.5 - Thermochemistry104
- Ch.6 - Electronic Structure of Atoms109
- Ch.7 - Periodic Properties of the Elements107
- Ch.8 - Basic Concepts of Chemical Bonding102
- Ch.9 - Molecular Geometry and Bonding Theories120
- Ch.10 - Gases122
- Ch.11 - Liquids and Intermolecular Forces79
- Ch.12 - Solids and Modern Materials102
- Ch.13 - Properties of Solutions99
- Ch.14 - Chemical Kinetics153
- Ch.15 - Chemical Equilibrium83
- Ch.16 - Acid-Base Equilibria109
- Ch.17 - Additional Aspects of Aqueous Equilibria117
- Ch.18 - Chemistry of the Environment60
- Ch.19 - Chemical Thermodynamics109
- Ch.20 - Electrochemistry113
- Ch.21 - Nuclear Chemistry79
- Ch.22 - Chemistry of the Nonmetals52
- Ch.23 - Transition Metals and Coordination Chemistry57
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry7
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
Chapter 13, Problem 50a
The density of toluene (C7H8) is 0.867 g/mL, and the density of thiophene (C4H4S) is 1.065 g/mL. A solution is made by dissolving 8.10 g of thiophene in 250.0 mL of toluene. (a) Calculate the mole fraction of thiophene in the solution.
Verified step by step guidance1
Step 1: Calculate the number of moles of each component. The number of moles is given by the formula: n = mass / molar mass. The molar mass of thiophene (C4H4S) is approximately 84.14 g/mol and the molar mass of toluene (C7H8) is approximately 92.14 g/mol.
Step 2: Use the given mass of thiophene (8.10 g) and the molar mass from step 1 to calculate the number of moles of thiophene.
Step 3: Use the given volume of toluene (250.0 mL), the density of toluene (0.867 g/mL), and the molar mass from step 1 to calculate the number of moles of toluene.
Step 4: The mole fraction of a component in a solution is given by the formula: X = n_component / n_total. Calculate the total number of moles (n_total) by adding the number of moles of thiophene and toluene.
Step 5: Substitute the number of moles of thiophene and the total number of moles into the formula from step 4 to calculate the mole fraction of thiophene in the solution.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mole Fraction
Mole fraction is a way of expressing the concentration of a component in a mixture. It is defined as the ratio of the number of moles of a specific component to the total number of moles of all components in the mixture. This concept is crucial for understanding the composition of solutions and is often used in calculations involving colligative properties.
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Mole Fraction Formula
Density and Volume Relationship
Density is defined as mass per unit volume and is a key property of substances. In this context, knowing the density of toluene allows us to convert the volume of toluene (250.0 mL) into mass, which is necessary for calculating the total number of moles in the solution. Understanding this relationship is essential for solving problems involving solutions and mixtures.
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Molar Mass Calculation
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To calculate the mole fraction of thiophene, we need to determine the number of moles of thiophene and toluene. This requires knowing the molar masses of both compounds, which can be calculated from their chemical formulas by summing the atomic masses of their constituent elements.
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Related Practice
Textbook Question
Calculate the number of moles of solute present in each of the following aqueous solutions: (b) 86.4 g of 0.180 m KCl,
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Textbook Question
The density of acetonitrile (CH3CN) is 0.786 g/mL and the density of methanol (CH3OH) is 0.791 g/mL. A solution is made by dissolving 22.5 mL of CH3OH in 98.7 mL of CH3CN. (c) Assuming that the volumes are additive, what is the molarity of CH3OH in the solution?
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Textbook Question
Calculate the number of moles of solute present in each of the following solutions: (a) 255 mL of 1.50 M HNO3(aq),
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Textbook Question
Ascorbic acid (vitamin C, C6H8O6) is a water-soluble vitamin. A solution containing 80.5 g of ascorbic acid dissolved in 210 g of water has a density of 1.22 g/mL at 55 °C. Calculate (c) the molality,
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Textbook Question
Calculate the number of moles of solute present in each of the following aqueous solutions: (c) 124.0 g of a solution that is 6.45% glucose (C6H12O6) by mass.
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