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Gas Stoichiometry

Gas Stoichiometry. Molar Volume. What is the volume of 1 L of gas at STP? 22.414 L This volume of 1 L at STP is called the molar volume of a gas It is the same for all gases at STP. Example. A sample of nitrogen has a volume of 1.75L at STP. How many moles of nitrogen are present?.

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Gas Stoichiometry

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  1. Gas Stoichiometry

  2. Molar Volume • What is the volume of 1 L of gas at STP? • 22.414 L • This volume of 1 L at STP is called the molar volume of a gas • It is the same for all gases at STP

  3. Example • A sample of nitrogen has a volume of 1.75L at STP. How many moles of nitrogen are present?

  4. Example • Calcium oxide is produced by the thermal decomposition of calcium carbonate. Calculate the volume of carbon dioxide at STP produced from the decomposition of 152 g if calcium carbonate.

  5. Example • A 2.55g sample of ammonium nitrite decomposes into nitrogen gas and water vapor. What volume of nitrogen gas will be collected if the temperature is 26ºC and the total pressure is 745mmHg?

  6. Gas Density • g/L is density • PV = nRT • n/V = P/ RT • M is molar mass • nM/ V = PM/ RT • nM is grams and g/ V is density • d = PM/ RT • M = dRT/ P

  7. Example 3 • What is the density of CO2 at 745mmHg and 65ºC?

  8. Example 4 • A large flask is evacuated and weighed, its mass if found to be 134.567g. It is then filled with a gas to a pressure of 735mmHg at 31ºC and reweighed; its mass is 137.456g. It is filled with water and the volume of the water is measured to be 936 cm3. What is the molecular weight of the gas?

  9. Partial Pressure • Pressure of individual gases in a mixture

  10. Daltons’ Law of Partial Pressures • The total pressure inside a container is equal to the partial pressure due to each gas. • The partial pressure is the contribution by that gas. • PTotal = P1 + P2 + P3

  11. 6 atm 1 atm 2 atm 3 atm

  12. Examples • What is the total pressure in a balloon filled with air if the pressure of the oxygen is 170 mm Hg and the pressure of nitrogen is 620 mm Hg? • In a second balloon the total pressure is 1.3 atm. What is the pressure of oxygen if the pressure of nitrogen is 720 mm Hg?

  13. More Examples • What pressure is exerted by a mixture of 2.00 g of hydrogen gas and 8.00 g of nitrogen gas at 273 K and in a 10.0 L vessel? • If a .20 L sample of oxygen at 0°C and 1 atm and a .10 L sample of nitrogen at 0°C and 2.0 atm are both placed in a .40 L container at 0°C, what is the total pressure of the mixture?

  14. Mole Fraction • Ratio of the number of moles of a component in a mixture to the total number of moles in the mixture • Numerically equal to the ratio of the partial pressure of a component gas to the total pressure of the gas mixture

  15. Example • The partial pressure of oxygen was observed to be 156 torr in air with a total atmospheric pressure of 743 torr. Calculate the mole fraction of oxygen in the sample.

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