Gas Laws Robert Boyle Jacques Charles Amadeo Avogadro

Gas Laws Robert Boyle Jacques Charles Amadeo Avogadro Joseph Louis Gay-Lussac

Factors that effect a GAS 1. The quantity of a gas, n, in moles 2. The temperature of a gas, T, in Kelvin (Celsius degrees + 273) 3. The pressure of a gas, P, in pascals 4. The volume of a gas, V, in cubic meters

The Mole The word “mole” is derived from Latin to mean “heap” or “pile”. It is basically a chemical counting unit. Below, what we have is called the Mole Road Map and it summarizes what a mole equals. Avogadro’s # = 6. 02 x 1023 Particles Atomic Mass from P. T 1 MOLE STP = Standard Temperature and Pressure ST = 0 degrees Celsius or 273 Kelvin SP = atmospheric pressure 22. 4 Liters gas @ STP

Example A flexible container of Oxygen(O 2) has a volume of 10. 0 m 3 at STP. Find the # moles and molecules that exist in the container 14, 285. 71 moles 8. 51 x 1029 particles

The Combined Gas Law The combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas. ● Pressure does not need to be converted to atm since it is in a ratio and the units of torr will cancel out. ● Temperature must be in Kelvins. Since this conversion involves an addition of 273, the conversion factor does not cancel. Be careful!

Boyle’s Law Pressure is inversely related to volume when temperature is held constant.

Charles’s Law • The volume of a gas is directly proportional to temperature, and extrapolates to zero at zero Kelvin. (P = constant) Temperature MUST be in KELVINS!

Gay Lussac’s Law The pressure and temperature of a gas are directly related, provided that the volume remains constant. Temperature MUST be in KELVINS!

Avogadro’s Law Equal volumes of gas at the same temperature and pressure have the same number of particles. 22. 4 L of ANY GAS at STP contains 6. 02 x 1023 particles

WHAT IS AN IDEAL GAS ? An ideal gas is defined as one in which there are no intermolecular forces between the atoms or molecules. . In such a gas, all the internal energy is in the form of kinetic energy and any change in internal energy is accompanied by a change in temperature. The ideal gas law works extremely well at high temperature and low pressure.

Ideal Gas Law PV = n. RT ❖P = pressure in atm ❖V = volume in liters ❖n = moles ❖R = proportionality constant ❖= 0. 08206 L atm/ mol·Κ • T = temperature in Kelvins

Gas Stoichiometry #1 If reactants and products are at the same conditions of temperature and pressure, then mole ratios of gases are also volume ratios. 3 H 2(g) + N 2(g) → 2 NH 3(g) 3 moles H 2 + 1 mole N 2 → 2 moles NH 3 3 liters H 2 + 1 liter N 2 → 2 liters NH 3

Gas Stoichiometry #2 How many liters of ammonia can be produced when 12 liters of hydrogen react with an excess of nitrogen? 3 H 2(g) + N 2(g) 12 L H 2 → 2 L NH 3 3 L H 2 2 NH 3(g) = 8. 0 L NH 3

Gas Stoichiometry #3 How many liters of oxygen gas, at STP, can be collected from the complete decomposition of 50. 0 grams of potassium chlorate? 2 KCl. O 3(s) → 2 KCl(s) + 3 O 2(g) 50. 0 g KCl. O 3 1 mol KCl. O 3 122. 55 g KCl. O 3 3 mol O 2 22. 4 L O 2 2 mol KCl. O 3 1 mol O 2 = 13. 7 L O 2 A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more elements or new compounds. These reactions often involve an energy source such as heat, light, or electricity that breaks apart the bonds of compounds.

Gas Density … so at STP…

Density and the Ideal Gas Law Combining the formula for density with the Ideal Gas law, substituting and rearranging algebraically: M = Molar Mass P = Pressure R = Gas Constant T = Temperature in Kelvins

Gas Density Calculations The density of a gas was measured at 1. 50 atm and 27 o. C and found to be 1. 95 g/L. Calculate the molar mass. Molar mass = drt (1. 95 g/ml) ( 0. 08206 L. atm) ( 300 K) P _______________ K. mol 1. 50 atm Molar mass = 32. 0 g/mol