CH8_6_Volume_and_Moles_Avogadros_Laws_GOB_Structures_5th_ed.pptx
- 1. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. 8.6 Volume and Moles, Avogadro’s Law The molar volume of a gas at STP is about the same as the volume of three basketballs. The volume of 1 mole of gas is 22.4 liters. Learning Goal Use Avogadro’s law to calculate the amount or volume of a gas when the pressure and temperature are constant.
- 2. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Avogadro’s Law: Volume and Moles In Avogadro’s law, • the volume of a gas is directly related to the number of moles (n) of gas. • T and P are constant.
- 3. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Calculations Using Avogadro’s Law If 0.75 mole of helium gas occupies a volume of 1.5 L, what volume (L) will 1.2 moles of helium occupy at the same temperature and pressure? A. 0.94 L B. 1.8 L C. 2.4 L
- 4. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Calculations Using Avogadro’s Law If 0.75 mole of helium gas occupies a volume of 1.5 L, what volume (L) will 1.2 moles of helium occupy at the same temperature and pressure? STEP 1 Organize the data into a table of initial and final conditions. Pressure and temperature remain constant.
- 5. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Calculations Using Avogadro’s Law STEP 2 Rearrange to solve for unknown quantity V2. STEP 3 Substitute the values into the gas law equation and calculate. The answer is C. × ×
- 6. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Standard Temperature and Pressure The volumes of gases can be compared at STP, Standard Temperature and Pressure, when they have • the same temperature. • a standard temperature (T) of 0 °C or 273 K. • the same pressure. • a standard pressure (P) of 1 atm (760 mmHg).
- 7. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Molar Volume, STP At standard temperature and pressure (STP), 1 mole of a gas occupies a volume of 22.4 L, which is called its molar volume. Use this equality as a conversion factor for gas at STP: 22.4 L = 1 mole gas
- 8. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Molar Volume Avogadro’s law indicated that1 mole of any gas at STP has a volume of 22.4 L.
- 9. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Guide to Using Molar Volume
- 10. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Calculations Using Molar Volume What is the volume occupied by 2.75 moles of N2 gas at STP? STEP 1 State the given and needed quantities. Pressure and temperature remain constant. STEP 2 Write a plan to calculate the needed quantity. Moles N2 Volume N2
- 11. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Calculations Using Molar Volume STEP 3 Write conversion factors including 22.4 L/mole at STP. At STP, 22.4 L = 1 mole N2. STEP 4 Set up the problem with factors to cancel units. ×
- 12. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Study Check 1. What is the volume at STP of 4.00 g of CH4? A. 5.60 L B. 11.2 L C. 44.8 L 2. How many grams of He are present in 8.00 L of gas at STP? A. 25.6 g B. 0.357 g C. 1.43 g
- 13. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Solution STEP 1 State given and needed quantities. 1. What is the volume at STP of 4.00 g of CH4? Pressure and temperature remain constant. 2. How many grams of He are present in 8.00 L of gas at STP? Pressure and temperature remain constant. ANALYZE Given Need THE 4.00 grams CH4(g) volume CH4(g) PROBLEM at STP at STP
- 14. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Solution STEP 2 Write a plan to calculate the needed quantity. 1. What is the volume at STP of 4.00 g of CH4? mass CH4 moles CH4 volume CH4 2. How many grams of He are present in 8.00 L of gas at STP? volume He moles He mass He
- 15. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Solution STEP 3 Write conversion factors including 22.4 L/mole at STP. 1. What is the volume at STP of 4.00 g of CH4? 22.4 L = 1 mole of CH4 1 mole of CH4 = 16.05 g CH4
- 16. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Solution STEP 3 Write conversion factors including 22.4 L/mole at STP. 2. How many grams of He are present in 8.00 L of gas at STP? 22.4 L = 1 mole of He 1 mole of He = 4.00 g He
- 17. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake © 2016 Pearson Education, Inc. Solution STEP 4 Set up the problem with factors to cancel units. 1. What is the volume at STP of 4.00 g of CH4? The answer is A, 5.60 L 2. How many grams of He are present in 8.00 L of gas at STP? The answer is C, 1.43 g. × × × ×