Textbook Question
Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. a. potassium chromate b. lead(II) phosphate
Ch.3 - Molecules and Compounds
Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217
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Table of contents
- Ch.1 - Matter, Measurement & Problem Solving118
- Ch.2 - Atoms & Elements106
- Ch.3 - Molecules and Compounds131
- Ch.4 - Chemical Reactions and Chemical Quantities56
- Ch.5 - Introduction to Solutions and Aqueous Solutions82
- Ch.6 - Gases114
- Ch.7 - Thermochemistry96
- Ch.8 - The Quantum-Mechanical Model of the Atom60
- Ch.9 - Periodic Properties of the Elements90
- Ch.10 - Chemical Bonding I: The Lewis Model89
- Ch.11 - Chemical Bonding II: Molecular Shapes, VSEPR & MO Theory85
- Ch.12 - Liquids, Solids & Intermolecular Forces51
- Ch.13 - Solids & Modern Materials47
- Ch.14 - Solutions90
- Ch.15 - Chemical Kinetics115
- Ch.16 - Chemical Equilibrium68
- Ch.17 - Acids and Bases136
- Ch.18 - Aqueous Ionic Equilibrium153
- Ch.19 - Free Energy & Thermodynamics93
- Ch.20 - Electrochemistry106
- Ch.21 - Radioactivity & Nuclear Chemistry74
- Ch.22 - Organic Chemistry140
Chapter 3, Problem 118
A drop of water has a volume of approximately 0.05 mL. How many water molecules does it contain? The density of water is 1.0 g/cm3.
Verified step by step guidance1
First, convert the volume of the water drop from milliliters to cubic centimeters (cm3) since the density of water is given in g/cm3. Remember that 1 mL is equivalent to 1 cm3.
Next, use the density of water to convert the volume of the water drop to mass. Density is defined as mass per unit volume, so you can multiply the volume of the water drop by the density of water to find the mass of the water drop in grams.
Then, convert the mass of the water drop to moles using the molar mass of water. The molar mass of water (H2O) is approximately 18.015 g/mol. You can do this by dividing the mass of the water drop by the molar mass of water.
After that, use Avogadro's number to convert the number of moles of water to the number of water molecules. Avogadro's number (6.022 x 10^23) is the number of particles (atoms, molecules, ions, etc.) in one mole of a substance.
Finally, calculate the number of water molecules in the drop of water by multiplying the number of moles of water by Avogadro's number.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Molar Mass of Water
The molar mass of water (H2O) is approximately 18.02 g/mol. This value is essential for converting grams of water to moles, which allows us to relate the mass of water to the number of molecules it contains. Since one mole of any substance contains Avogadro's number of entities (approximately 6.022 x 10^23), knowing the molar mass is crucial for calculating the total number of water molecules in a given volume.
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Molar Mass Concept
Density and Volume Relationship
Density is defined as mass per unit volume, and for water, it is approximately 1.0 g/cm³. This means that 1 mL of water has a mass of about 1 gram. Understanding this relationship allows us to convert the volume of water (0.05 mL) into mass, which is necessary for further calculations involving the number of molecules.
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Avogadro's Number
Avogadro's number (6.022 x 10^23) is the number of atoms, ions, or molecules in one mole of a substance. This constant is fundamental in chemistry for converting between moles and the number of individual particles. Once we determine the number of moles of water from its mass, we can use Avogadro's number to find the total number of water molecules present in the drop.
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Related Practice
Textbook Question
Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. c. nitrogen triiodide
Textbook Question
Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. c. sulfurous acid
Textbook Question
How many molecules of ethanol (C2H5OH) (the alcohol in alcoholic beverages) are present in 145 mL of ethanol? The density of ethanol is 0.789 g/cm3.
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