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The Mole: A Measurement of Matter

Understand the concept of a mole and Avogadro's number, and learn how to solve problems involving mass, moles, and the number of atoms. Also, explore the calculation of molar mass.

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The Mole: A Measurement of Matter

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  1. The Mole: A Measurement of Matter Describe how Avogadro’s number is related to a mole of any substance Solve problems involving mass in grams, amount in moles, and number of atoms of an element

  2. The Mole and Avogadro’s Number • SI unit that measures the amount of substance • 1 mole = 6.022 x 1023 representative particles • Representative particles are usually atoms, molecules, or formula units (ions)

  3. Examples

  4. Solve • How many atoms are in one mole of 1. Mercury (Hg) 2. Gold (Au) 3. Silver (Ag) 4. Iron (Fe)

  5. How many moles of magnesium are in 1.25 x 1023 atoms of magnesium? • Divide the number of atoms or molecules given in the example by 6.022 x 1023 • Divide (1.25 x 1023) by (6.022 x 1023) • Express in scientific notation • Answer = 2.08 x 10-1 mol Mg

  6. How many moles of silver, Ag, are in 3.01 x 1023 atoms of silver?

  7. Answer 0.500 mol Ag

  8. Molar mass • Mass (in grams) of one mole of a substance • Broad term (can be substituted) for gram atomic mass, gram formula mass, and gram molecular mass • Can be unclear: What is the molar mass of oxygen? O or O2 ? - element O or molecular compound O2 ?

  9. Molar Mass • The mass of one mole of atomic hydrogen is 1.01 grams. • The mass of one mole of aluminum is 26.98. • What is the mass of one mole of barium? Zinc? Neon?

  10. Calculating the Molar Mass • What is the mass in grams of 3.50 mol of the element copper? 1. Look up the mass on the periodic table. Round it to two decimal places. (63.55 g) 2. Multiply 63.55 g by 3.50 moles. • Answer is 222 g Cu (Three significant figures because three figs in 3.50)

  11. Solve • What is the mass in grams of 2.00 mol of nitrogen?

  12. Solve • What is the mass in grams of 1.20 x 108 atoms of copper, Cu? 1. Convert the given amount of atoms to the amount of moles by dividing by Avogadro’s number. Answer: 1.99 x 10-16 2. The amount in moles is then multiplied by molar mass (63.55) • Answer: 1.27 x 10-14 g Cu

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