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Lesson 2: The Molar Relationships

Lesson 2: The Molar Relationships. Unit 8 – Moles and Stoichiometry. Molar Relationships. We can convert between moles, N A , molar mass and volume using molar relationships and dimensional analysis . Relationships: grams and moles grams and representative particles

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Lesson 2: The Molar Relationships

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  1. Lesson 2:The Molar Relationships Unit 8 – Moles and Stoichiometry

  2. Molar Relationships • We can convert between moles, NA, molar mass and volume using molar relationships and dimensional analysis. • Relationships: grams and moles grams and representative particles moles and representative particles moles and liters

  3. “Two-Step” Conversion Problem? • Molar conversions require a two-step conversion. • One to convert from given unit to moles • One to convert from moles to wanted unit

  4. Molar RelationshipsGrams and Moles molar mass Mass in Grams Moles (g/mol)

  5. The Four Steps to Solving Mole Problems • Step 1: Figure out how many parts your calculation will have by using the mole map diagram. • Step 2: Make a T-chart, and put whatever information the problem gave you in the top left. After that, put the units of whatever you were given in the bottom right of the T, and the units of what you want to find in the top right.

  6. The Four Steps to Solving Mole Problems • Step 3: Put the conversion factors into the T-chart in front of the units on the right. Use your mole map diagram. • Step 4: Cancel out the units from the top left and bottom right, then find the answer by multiplying all the stuff on the top together and dividing it by the stuff on the bottom.

  7. Converting Moles to Grams How many grams of lithium are in 3.50 moles of lithium? 3.50 mol Li 1 6.94 g Li = g Li 24.29 1 mol Li

  8. Converting grams to moles How many moles of lithium are in 18.2 grams of lithium? 18.2 g Li 1 1 mol Li = mol Li 2.62 6.94 g Li

  9. Converting Moles to Mass in a Compound • How many grams of calcium chloride are in 0.98moles of calcium chloride? .98mole CaCl2 110.98g CaCl2 1mole CaCl2 = 108.76 g CaCl2 1

  10. MOLES Molar RelationshipRepresentative Particles and Moles 6.02  1023 NUMBER OF PARTICLES NUMBER OF PARTICLES (particles/mol)

  11. Converting Moles to Number of representative particles 1. How many molecules are in 2.50 moles of C12H22O11? 6.02  1023 molecules 1 mol 2.50 mol = 1.51  1024 molecules C12H22O11

  12. How many atoms of lithium are in 3.50 moles of lithium? 3.50 mol Li 6.02 x 1023 atoms Li = atoms Li 2.11 x 1024 1 mol Li

  13. Converting Number of Representative Particles to mole Calculate the moles of Aluminum Oxide in 2.0 x1024 molecules 2.0 x 1024 molecules 1 mole = 3.32 mole of Aluminum Oxide 6.02  1023 molecules

  14. MASS IN GRAMS MOLES NUMBER OF PARTICLES Molar RelationshipGrams and Representative Particles molar mass 6.02  1023 (g/mol) (particles/mol)

  15. Molecules to Grams • Find the mass of 2.1  1024 molecules of NaHCO3. 1 mol NaHCO3. 6.02  1023 molecules 2.1  1024 Molecules 1 84.01 g 1 mol = 293.06 g NaHCO3 2.9x102

  16. Grams to Molecules • Find the number of molecules in 5 grams of MgSO4. 1 mol MgSO4 120.37g 5 grams MgSO4 1 6.02  1023 molecules 1 mol = 2.50  1022 molecules MgSO4

  17. Molar RelationshipsVolume and Moles Molar volume Molar volume Moles (22.4 L/mol)

  18. Avogadro’s Law Molar Volume of Gases • equal volumes of gases at the same Temperature and Pressure contain equal numbers of molecules • at same T and P, volumes varies directly with number of moles (n)

  19. Molar Volume of Gases • like molar mass • mass of one mole of substance • but with volume • volume of one mole of substance • because of Avogadro’s law, one mole of any gas has the same volume as any other gas at the same T and P

  20. Molar Volume of Gases • Standard Temperature and Pressure • STP • 1 atm and 0°C • Standard Molar Volume of Gas • volume of one mole of gas at 1 atm and 0°C is 22.4L • 22.4 L of any gas has one mole of particles but has different masses

  21. Moles to Volume • A chemical reaction produces 0.0680 mol of oxygen gas. What volume in liters is occupied by this gas sample at STP? • 1 mol : 22.4 L

  22. Molar Volume Problems • How many liters of Oxygen gas are in 5.0 moles Oxygen at STP? 5.0 mol 1 22.4L = 112.00L 1 mol

  23. Volume to Mass • A chemical reaction produced 98.0 mL of sulfur dioxide gas at STP. What was the mass of gas made?

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