This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
• In your study of chemistry, you will analyze the composition of samples of matter and perform chemical calculations that relate quantities of the reactants in a chemical reaction to quantities of the products.
• To solve these and other problems, you will have to be able to measure the amount of matter you have.
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
Knowing how the count, mass, and volume of an item relate to a common unit allows you to convert among these units.
• For example, based on the unit relationship, you could calculate the mass of a bushel of apples or the mass of 90 average-sized apples using conversion factors such as the following:
12 apples
1 dozen apples
1 dozen apples
2.0 kg apples
0.20 bushel apples
1 dozen apples
Measuring MatterMeasuring Matter
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
A dozen apples has a mass of 2.0 kg, and 90 apples is less than 10 dozen apples, so the mass should be less than 20 kg of apples (10 dozen x 2.0 kg/dozen).
Sample Problem 10.1Sample Problem 10.1
Evaluate Does the result make sense?3
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
If you know the mass of a bushel of apples and the mass of a single apple, what other information can you calculate?
You can calculate the number of apples in a bushel by setting up the information you have as units with a common unit. “kg apples” will be the common unit.
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
What are the different ways you can measure the amount of sand in a sand sculpture?
You can measure the amount of sand in a sand sculpture by count (for example, number of buckets of sand in the sculpture), by mass (which can be calculated by multiplying the number of buckets of sand by how much each bucket weighs), or by volume (which can be calculated by multiplying the number of buckets by the volume the bucket holds).
CHEMISTRY & YOUCHEMISTRY & YOU
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
The relationship 1 mol = 6.02 × 1023 representative particles is the basis for the following conversion factors that you can use to convert numbers of representative particles to moles and moles to number of representative particles.
What Is a Mole?What Is a Mole?
Converting Between Number of Particles and Moles
1 mol
6.02 × 1023 representative particles
6.02 × 1023 representative particles
1 mol
and
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
Magnesium is a light metal used in the manufacture of aircraft, automobile wheels, and tools. How many moles of magnesium is 1.25 × 1023 atoms of magnesium?
Sample Problem 10.2Sample Problem 10.2
Converting Number of Atoms to Moles
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
• The given number of atoms (1.25 × 1023) is less than one-fourth of Avogadro’s number (6.02 × 1023), so the answer should be less than one-fourth (0.25) mol of atoms.
• The answer should have three significant figures.
Sample Problem 10.2Sample Problem 10.2
Evaluate Does the result make sense?3
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
In the formula for carbon dioxide (CO2), the subscripts show that one molecule of carbon dioxide is composed of three atoms: one carbon atom and two oxygen atoms.
• A mole of carbon dioxide contains Avogadro’s number of CO2 molecules.
• Each molecule contains three atoms, so a mole of carbon dioxide contains three times Avogadro’s number of atoms.
What Is a Mole?What Is a Mole?
Converting Between Number of Particles and Moles
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
To find the number of atoms in a given number of moles of a compound, you must first determine the number of representative particles.
• To convert the number of moles of a compound to the number of representative particles (molecules or formula units), multiply the number of moles by 6.02 × 1023 representative particles/1 mol.
• Then multiply the number of representative particles by the number of atoms in each molecule or formula unit.
What Is a Mole?What Is a Mole?
Converting Between Number of Particles and Moles
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
• There are 11 atoms in each molecule of propane and more than 2 mol of propane, so the answer should be more than 20 times Avogadro’s number of propane molecules.
• The answer has three significant figures, based on the three significant figures in the given measurement.
Sample Problem 10.3Sample Problem 10.3
Evaluate Does the result make sense?3
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
Both “mole” and “dozen” are quantities made of a specified number of “representative particles.” They both refer to multiple objects or particles that are now being thought of as a single object or particle with multiple parts.
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
The mole can now be further defined as the amount of substance that contains the same number of representative particles as the number of atoms in 12.0 g of carbon-12.
• You know that 12.0 g is the molar mass of carbon-12, so 12.0 g of carbon is 1 mol of carbon atoms.
• Similarly, 24.3 g is the molar mass of magnesium, so 1 mol (or 6.02 × 1023 atoms of magnesium) has a mass of 24.3 g.
• Molar mass is the mass of 1 mol of atoms of any element.
Molar MassMolar Mass
The Mass of a Mole of an Element
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound.
Molar MassMolar Mass
The Mass of a Mole of a Compound
• This method for calculating molar mass applies to any compound, molecular or ionic.
• The molar masses in the following slide were obtained in this way.
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
mass of 1 mol H = 1.0 g Hmass of 1 mol O = 16.0 g O
UNKNOWNmolar mass = ? g/mol
Convert moles of atoms to grams by using conversion factors (g/mol) based on the molar mass of each element. The sum of the masses of the elements is the molar mass.
Sample Problem 10.4Sample Problem 10.4
Analyze List the knowns and the unknown.1
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
The atomic mass of an element expressed in grams is the mass of a mole of the element.
To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound.
Key ConceptsKey Concepts
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter
• mole (mol): the amount of a substance that contains 6.02 × 1023 representative particles of that substance
• Avogadro’s number: the number of representative particles contained in one mole of a substance; equal to 6.02 × 1023 particles
• representative particle: the smallest unit into which a substance can be broken down without a change in composition, usually atoms, molecules, or ions
• molar mass: a term used to refer to the mass of a mole of any substance
Glossary TermsGlossary Terms
10.1 The Mole: A Measure-10.1 The Mole: A Measure-ment of Matterment of Matter