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Defining the Mole & Mole Practice Problems

Defining the Mole & Mole Practice Problems. Kelsey Flynn B Block May 2010. The Mole. Using a unit called mole ( also written as mol) Particles such as atoms, molecules and ions, can be counted three ways by the: the mole gives the number of particles mass of particles, or

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Defining the Mole & Mole Practice Problems

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  1. Defining the Mole & Mole Practice Problems Kelsey Flynn B Block May 2010

  2. The Mole • Using a unit called mole ( also written as mol) • Particles such as atoms, molecules and ions, can be counted three ways by the: • the mole gives the number of particles • mass of particles, or • the volume of the gas particles

  3. Avogadro’s Number 23 • A mole of a substance, an element or a compound, contains the same number of particles, 6.02 x 1023. 6.02 x 10 Particles One mole =

  4. Practice Questions! 1. How many moles are in 6.5 x 1021 molecules of CO Answer: 6.5 x 1021 molecules of CO x 1 mol of CO = 0.012 mol CO 6.02 x 1023 molecules of CO 2. How many molecules of H2O is needed to make 0.95 mole of it. Answer: 0.95 mole of H2O x 6.02 x 1023 molecules H2O= 5.72 x 1023 molecules H2O 1 mole H2O 3. How many atoms are present in 2.25 mole of Fluorine. Answer: 2.25 mole of Fluorine x 6.02 x 1023 atoms F= 1.35 x 1024 atoms F 1 mole F

  5. Molar Mass • The atomic mass of an atom is found on a periodic table, it is measured in a.m.u. The molar mass of an element, is measured in grams, is the same as the atomic mass. • Ex: Oxygen atomic mass =16 a.m.u molar mass = 16 g

  6. Molar Mass • The molar mass of a compound is the sum of the masses of all the elements in the compound. • A mole is measured in grams. • Ex: Nitrous Acid, HNO2 Molecular mass Molar Mass H= 1 a.m.u H= 1 g N= 14 a.m.u N= 14 g O2= 32 a.m.uO2= 32 g 47 a.m.u 47g molecular mass of molar mass of HNO2is 47 g HNO2is 47 a.m.u

  7. Practice Questions! How many grams of each element do you need to get one mol? 1. Xenon Answer: 131.29g 2. Silver Answer: 107.87g 3. Tin Answer: 118.71g

  8. Molar Volume • The volume of gases can be measured at SATP, standard ambient temperature and pressure. • At SATP, one mole of a gas occupies a volume of 24.8 L. That is the molar volume. • The unit for molar volume is L/mol.

  9. Molar Volume One mol of gas = 24.8 L at SATP SATP = 25º C = 298.15K or 100 kPa

  10. Practice Questions! 1. Find the volume of 0.5 moles of CO2 at SATP. Answer: 0.5 moles of CO2 x 24. 8 L of CO2 = 12.4 L CO2 1 mole CO2 2. How many moles are there in 4.75 L of a gas at SATP? Answer: 4.75 L of a gas x 1 mole of a gas = 0.2 mole of a gas 24.8 L of a gas 3. What is the density (g/L) of NH4 at SATP? Answer: NH4 density (g/L) = 18 g NH4 = 0.73 NH4 g/L 24.8 L NH4

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