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Chapter 7

Chapter 7. What is a mole? In chemistry one way to count substances is by something called a mole. Like a dozen, a mole is a certain number of atoms and a certain mass of atoms. A mole represents 6.02 x 10 23 particles of a substance. Just like a dozen = 12 of something.

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Chapter 7

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  1. Chapter 7 • What is a mole? • In chemistry one way to count substances is by something called a mole. • Like a dozen, a mole is a certain number of atoms and a certain mass of atoms. • A mole represents 6.02 x 10 23 particles of a substance. • Just like a dozen = 12 of something. • A mole of something contains 6.02 x 10 23 atoms, ions, particles or molecules or whatever. This is referred to as Avagadro’s number.

  2. What is a mole • Movie

  3. A mole of anything is a huge number of things. 602 with 21 zeroes after it. • 1 mole of a substance = atomic mass of an element in grams. • a mole of carbon atoms = 12 grams of carbon • a mole of oxygen atoms = 16 grams of oxygen

  4. However oxygen doesn’t run around as O it is diatomic remember. O2. • 1 mole of O2 = 2(16) grams = 6.02 x 10 23 molecules of O2 = 2(6.02 x 10 23) atoms of O

  5. What would the mass of 1 mole of the following be? • Carbon dioxide • Bromine • hydrogen • SO3

  6. What would the mass of 1 mole of the following be? • Nitrogen •  Sodium hydroxide • Aluminum sulfate • Barium nitrate

  7. What we just found is also called the gram molecular mass for molecular compounds and the gram formula mass for ionic compounds. • All the terms for mass we have been using can be combined to be called molar mass.

  8. What is the mass in grams of 1.72 mole of calcium chloride? • How many moles is 24.6 g of water?

  9. Volumes of gases change with temperature and pressure. So when we talk about the volume of a gas we talk about it at Standard Temperature and Pressure. STP • Standard Temperature = 0 C or 273 K • Standard Pressure = 101.3 kpascal or 1 atmosphere (atm) • 1 mole of gas at STP = 22.4 liters = 6.02 x 10 23 particles

  10. Since density is measured in mass /volume we can use density to find the mass of a substance.

  11. % Composition and Chemical formulas • Knowing the relative amounts of the components of a mixture or compound is often useful or important. • The relative amount of each element in a compound are expressed as % composition. • % of an element = # of grams of the element/ mass of compound X 100

  12. movie

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