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Gay Lussac’s law of combining volumes of gases

Gay Lussac’s law of combining volumes of gases. When gases combine, they combine in simple whole number ratios. These simple numbers are the coefficients of the balanced equation. N 2 + 3H 2 2NH 3 3 volumes of hydrogen will produce 2 volumes of ammonia.

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Gay Lussac’s law of combining volumes of gases

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  1. Gay Lussac’s law of combining volumes of gases • When gases combine, they combine in simple whole number ratios. • These simple numbers are the coefficients of the balanced equation. N2 + 3H2 2NH3 • 3 volumes of hydrogen will produce 2 volumes of ammonia Mullis

  2. Avogadro’s Law and Molar Volume of Gases • Equal volumes of gases (at the same temp and pressure) contain an equal number of molecules. In the equation for ammonia formation, 1 volume N2 = 1 molecule N2 = 1 mole N2 • One mole of any gas will occupy the same volume as one mole of any other gas • Standard molar volume of a gas is the volume occupied by one mole of a gas at STP. Standard molar volume of a gas is 22.4 L. Mullis

  3. Sample molar volume problem • A chemical reaction produces 98.0 mL of sulfur dioxide gas at STP. What was the mass, in grams, of the gas produced? ***Turn mL to L first! (This way, you can can use 22.4 L) 98 mL 1 L 1 mol SO2 64.07g SO2 = 0.280g SO2 1000 mL 22.4 L 1 mol SO2 Mullis

  4. Sample molar volume problem 2 What is the volume of 77.0 g of nitrogen dioxide gas at STP? 77.0 g NO2 1 mol NO2 22.4 L = 37.5 L NO2 46.01g NO2 1 mol NO2 Mullis

  5. Ideal Gas Law • Mathematical relationship for PVT and number of moles of gas PV = nRT n = number of moles R = ideal gas constant P = pressure V = volume in L T = Temperature in K R = 0.0821 if pressure is in atm R = 8.314 if pressure is in kPa R = 62.4 if pressure is in mm Hg Mullis

  6. Sample Ideal Gas Law Problem • What pressure in atm will 1.36 kg of N2O gas exert when it is compressed in a 25.0 L cylinder and is stored in an outdoor shed where the temperature can reach 59°C in summer? V = 25.0 L T = 59+273 = 332 K P = ? R = 0.0821L-atm n = 1.36 kg converted to moles mol-K • 1.36 kg N2O 1000 g 1 mol N2O = 30.90 mol N2O 1 kg 44.02 g N2O • PV = nRT • P = 30.90 mol x 0.0821 L-atm x 332 K = 33.7 atm 25.0 L mol-K Mullis

  7. Volume-Volume Calculations • Volume ratios for gases are expressed the same way as mole ratios we used in other stoichiometry problems. N2 + 3H2 2NH3 Volume ratios are: 2 volumes NH33 volumes H2 2 volumes NH3 3 volumes H2 1 volume N2 1 volume N2 Mullis

  8. Sample Volume-Volume Problem • How many liters of oxygen are needed to burn 100 L of carbon monoxide? 2CO + O2 2CO2 100 L CO 1 volume O2 = 50 L O2 2 volume CO Mullis

  9. Sample Volume-Volume Problem 2 Ethanol burns according to the equation below. At 2.26 atm and 40° C, 55.8 mL of oxygen are used. What volume of CO2 is produced when measured at STP? C2H5OH + 3O2 2CO2 + 3H2O Number moles oxygen under these conditions is? PV = nRT: 2.26 atm(.0558L) = n = 0.0049 mol O2 (0.0821 L-atm)(313K) mol-K 0.0049 mol O2 2 mol CO2 22.4 L =0.073 L CO 2 3 mol O2 1 mol CO2 Mullis

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