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Science 10H

Science 10H. Chem Extra #2: Mole Conversions. Objectives. By the end of the lesson you should be able to: Relate moles to the volume of a gas Convert between moles, mass, # of particles and volume of a gas Convert using densities not at STP. Avogadro’s Hypothesis.

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Science 10H

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  1. Science 10H Chem Extra #2: Mole Conversions

  2. Objectives By the end of the lesson you should be able to: • Relate moles to the volume of a gas • Convert between moles, mass, # of particlesand volume of a gas • Convert using densities not at STP

  3. Avogadro’s Hypothesis Equal volumes of different gases, at the same temperature and pressure, contain the same number of particles • All gas samples with the same pressure, temperature and # of particles will occupy the same volume • STP: standard temperature and pressure (0oC and 101.3 kPa)

  4. STP • 1 mol of ANY GAS at STP has a volume of 22.4L • CONVERSION FACTOR: 1 mol or 22.4L 22.4L 1 mol

  5. Practice • What is the volume occupied by the following gases at STP: • 0.350 mol of SO2(g) • 12.5 mol of NH3 (g) • 0.350 mol of O2 (g) • 4.25 mol of HCl (g)

  6. Practice 2. Calculate the number of moles of the following gases at STP: • 10.0 L • 85.9 L of H2(g) • 375 mL of SO3 (g) • 5.00 mL of OCl2 (g)

  7. Recall… • CONVERSION FACTOR: 1mol or 6.02 X 1023molecules 6.02 X 1023molecules 1 mol Using the above conversion factor could we figure out how many molecules are in 0.125 mol of molecules? YEP we can!!! Let’s figure it out!! 

  8. More Practice….. • How many moles of N atoms are there in 5.00 x 1017 N atoms? • A light source emits 8.50 X 1017 photons per second. How many moles of photons are emitted by the light source in one minute? • A particular variety of C atom has a mass of 2.16 X 10-23 g/atom. What is the mass of a mole of this variety of C atom? Worksheet time!!

  9. Atoms and Molecules… • Before we can jump into more complex conversions we need to understand how to calculate how many atoms are in a molecule i.e. how many atoms are there in 5 molecules of CuSO4∙5H2O? Step 1: how many in one molecule? 21 Step 2: multiple it up! # of atoms = 5 molecules X 21 atoms = 105 atoms molecule

  10. Atoms and Molecules CONVERSION FACTOR: # atoms or 1 molecule. 1 Molecule # atoms

  11. Practice 1. Calculate how many atoms are contained in 3 molecules of each of the following: • CH3CO2H • NH4Cl • (CH3)2CO • (NH4)2SO4 • Ni(H2O)4(NH3)2Cl2

  12. Toughies!! • Up until now we have only done single stepper conversions (1 step conversions)….. • We must always convert from our given units into moles and then into our final units. • The MOLE is central to all conversions!! • Let’s use an overview to help!

  13. OVERVIEW! MASS OF A SUBSTANCE MOLAR MASS OF SUBSTANCE MOLES (of a substance) AVOGADRO’S NUMBER PARTICLES OF A SUBSTANCE MOLAR VOLUME VOLUME OF A SUBSTANCE

  14. Practice… • What is the volume occupied by 50.0 g of NH3 (g) at STP? • What is the mass of 1.00 X 1012 atoms of Cl? • How many oxygen atoms are contained in 75.0 L of SO3(g) at STP? Toughie Practice Time!

  15. DENSITY ISSUES! • So far we have only looked at gases at STP….but sometimes they aren’t going to be! • They will indicate this by including the density! • RECALL: d = m v

  16. Density examples: • What is the volume occupied by 3.00 mol of CH3CH2OH(l)? (d = 0.790 g/ml) • How many moles of Hg(l) are contained in 100 mL of Hg(l)? (d = 13.6 g/ml) • What is the density of O2 at STP? • A 2.50 L bulb contains 4.01g of a gas at STP. What is the molar mass of the gas? • Al2O3(s) has a density of 3.97 g/ml. How many atoms of Al are in 100 mL of Al2O3?

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