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## The Mole Concept

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**How can words be used to represent numbers?**• One example is the word “gross”. If you have a gross of something, you have 12 dozen or 144 items. • Can you think of any other words that are used to represent specific numbers?**What is a mole?**• Chemists must work with large groups of atoms due to their small size just as bakers work with groups of 12. • Chemists called their group a mole (just as bakers call their group a dozen). • How many objects make up a mole? • A mole = 602,000,000,000,000,000,000,000 or 6.02 x 1023**How large is 6.02 x 1023?**• A mole of paperclips hooked together in a chain would circle the earth 50 trillion times. • A mole of marshmallows would make a 12 mile thick layer covering the entire face of the earth. • A mole of popcorn kernels could cover the USA and be 5 miles deep. • If you could spend 1 billion dollars a second, it would take you 19 million years to spend a mole of dollar bills. • If you could count atoms at a rate of 1 million a second, it would take 20 billion years to count a mole of them.**Moles of Substances**• Count the number of beans in your bag. Compare with the person sitting next to you. • What do your samples have in common? • What is different about your samples? • How many dozen beans are in your bag? • Observe the samples of zinc, aluminum, copper, carbon, and sulfur. • What do the samples have in common? • What is different about the samples? • How is the volume different if the number of particles in each is the same?**12 atoms of carbon is one**10 • pair • dozen • mole • ream**If I have 1 mole of apples, I have how many?**10 • 12 • 500 • 1 x 106 • 6.02 x 10 23**2 dozen eggs is equal to how many?**10 • 2 • 24 • 100 • 12.04 x 1023**½ a mole of aluminum atoms is how many?**10 • 0.5 • 6 • 3.01 x 10 23 • 3.01 x 10 12**18.06 x 1023 molecules of water is how many moles?**10 • 18 • 23 • 1.5 • 3**Why is a mole = 6.02 x 1023?**• What is the mass of 1 carbon atom? • 12 amu (12 atomic mass units) • The atomic mass scale is a relative scale based on the carbon atom. • The masses of all other atoms are based on how their masses compare to carbon’s. • For example, magnesium is twice as heavy as a carbon atom. What is its mass? • 24 amu • Hydrogen was discovered to be 1/12 the mass of carbon, so its mass is 1 amu. • A chlorine atom is approximately 3 times as heavy as a carbon atom so its mass is approximately 36 amu.**Why is a mole = 6.02 x 1023?**• In the lab, scientists measure the amount of matter in terms of grams. • Therefore, chemists wanted to know how many atoms of carbon would be needed to have a mass of 12 g. • A professor by the name of Amadeo Avogadro determined this number to be 6.02 x 1023. • This number is now referred to as Avogadro’s number.**How can the concept of a mole be used to count atoms?**• 1 mole of carbon = 6.02 x 1023 atoms of carbon = 12 grams of carbon • 1 mole of hydrogen = 6.02 x 1023 atoms of hydrogen= 1 gram of hydrogen • 1 mole of aluminum = 6.02 x 1023 atoms = 27 grams**How can the concept of a mole be used to count atoms?**• 2 moles of carbon = 12.04 x 1023 atoms of carbon = 24 grams of carbon • ½ a mole of carbon = 3.01 x 1023 atoms of carbon= 6 grams of carbon • 3 moles of carbon = 18.06 x 1023 atoms = 36 grams • 1.5 moles of carbon = 9.03 x 1023 atoms = 18 grams**1 mole of sodium = ___ grams.**10 • 11 • 23 • 6.02 x 10 23 • 1**2 moles of oxygen = ___ atoms.**10 • 2 • 16 • 32 • 12.04 x 1023**If I have 2 grams of hydrogen, I have ___ atoms.**10 • 2 • 3.01 x 1023 • 6.02 x 1023 • 12.04 x 1023**The mole concept and compounds**• 1 dozen of water molecules is how many? • 12 • How many molecules are in 1 mole of water (H20)? • 6.02 x 1023 • What is the mass of 1 molecule of water? • 18 amu • What is the mass of 1 mole of water? • 18 grams • How many molecules are in 2 moles of water? • 12.04 x 10 23 • What is the mass of 2 moles of water? • 36 grams**1 molecule of carbon dioxide has a mass of**10 • 28 amu • 28 grams • 44 amu • 44 grams**1 mole of carbon dioxide is**10 • 28 amu • 28 grams • 44 amu • 44 grams**2 moles of carbon dioxide is ___ molecules.**10 • 44 • 88 • 6.02 x 10 23 • 12.04 x 1023**0.5 moles of carbon dioxide is ___ grams.**10 • 22 • 44 • 3.01 x 10 23 • 6.02 x 1023