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MOLECULAR COMPOSITION OF GASES. GAY-LUSSAC’S LAW OF COMBINING GAS VOLUMES. UNDER THE SAME CONDITIONS OF PRESSURE AND TEMPERATURE, THE VOLUMES OF REACTING GASES AND THEIR GASEOUS PRODUCTS ARE EXPRESSED IN RATIOS OF SMALL WHOLE NUMBERS.
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GAY-LUSSAC’S LAW OF COMBINING GAS VOLUMES • UNDER THE SAME CONDITIONS OF PRESSURE AND TEMPERATURE, THE VOLUMES OF REACTING GASES AND THEIR GASEOUS PRODUCTS ARE EXPRESSED IN RATIOS OF SMALL WHOLE NUMBERS. • THE RATIOS COME FROM THE COEFFICIENTS FOUND IN THE BALANCED EQUATION.
WHAT DO THESE RATIOS EXPRESS? • THEY EXPRESS: • ATOM AND MOLECULE RATIOS • MOLE RATIOS, AND • VOLUME RATIOS (IF THE SUBSTANCES ARE GASES AT THE SAME TEMPERATURE AND PRESSURE).
EXAMPLE • THE EQUATION 2 H2O 2 H2 + O2, TELLS US ALL OF THE FOLLOWING: • 2 MOLECULES OF WATER WILL DECOMPOSE INTO 2 MOLECULES OF HYDROGEN AND 1 MOLECULE OF OXYGEN, AND • 2 MOLES OF WATER WILL DECOMPOSE INTO 2 MOLES OF HYDROGEN AND 1 MOLE OF OXYGEN, AND • 2 LITERS OF WATER WILL DECOMPOSE INTO 2 LITERS OF HYDROGEN AND 1 LITER OF OXYGEN.
SAMPLE PROBLEM • FOR THE REACTION: NITROGEN + OXYGEN DINITROGEN PENTOXIDE, ASSUME YOU HAVE 50.0 g OF OXYGEN. • HOW MANY GRAMS AND LITERS OF DINOTROGEN PENTOXIDE COULD BE PRODUCED IF ALL OF THE OXYGEN WERE CONSUMED?
SAMPLE CON’T • HOW MANY GRAMS AND LITERS OF NITROGEN WOULD BE NEEDED TO USE UP ALL OF THE OXYGEN?
STANDARD MOLAR VOLUME OF A GAS • ONE MOLE OF ANY GAS (MEASURED AT STP) WILL OCCUPY A VOLUME OF 22.4 L. • SO: 1 MOLE OF He = 6.02 X 1023 ATOMS OF He = 4.00 g He = 22.4 L @ STP. • USING THE ABOVE INFO DETERMINE THE DENSITY OF He GAS AT STP.
STANDARD MOLAR VOLUME CON’T • FILL IN THE FOLLOWING: • 1 MOLE OF CO2 =___________ MOLECULES OF CO2 = _________g CO2 = 22.4 L CO2 @ STP. • DETERMINE THE DENSITY OF CO2 AT STP.
DO THE FOLLOWING PROBLEMS • PRACTICE #1 PAGE 336 • #3 PAGE 337 TOP • PRACTICE #1 PAGE 337 • #3 PAGE 337 AT BOTTOM • #1 AND #2 PG 343