Avogadro's law states that equal volumes of gases at the same temperature and pressure contain the same number of molecules. The ideal gas law combines Boyle's, Charles', Gay-Lussac's and Avogadro's gas laws into one equation, PV=nRT, which relates the pressure (P), volume (V), number of moles (n), temperature (T) of an ideal gas. The ideal gas law accurately describes gas behavior at normal room temperature and pressure but real gases deviate from ideal behavior at high pressures due to intermolecular forces or at low temperatures where particle volume is significant.

1. Molecular Composition of Gases Objectives State Avogadro’s Law and explain its importance Solve problems using the ideal gas law

2. Avogadro’s Law So far, we have studied three gas laws: Boyle’s Charles’ Gay-Lussac’s A fourth law, called Avogadro’s Law , gives us a relationship between the volume of a gas and the number of moles of that gas (at the same temp and pressure)

3. Avogadro’s Law naturally, this law has a formula: V = kn where V= volume k = the proportionality constant (same for all gases) n = number of moles of gas In plain English, it states "Equal volumes of ideal or perfect gases, at the same temperature and pressure, contain the same number of molecules."

4. Avogadro’s Law and its Significance Avogadro’s Law isn’t so much used to calculate as it is used to explain the relationship between the volume of any gas at STP. It has been determined that 22.41 L of argon at 0°C and 1 atm has a mass of 39.95 g Therefore, 22.41 L is the volume of 1 mole of any gas at STP.

5. The Ideal Gas Law No gas perfectly follows all four gas laws under all conditions. However, the assumption that they do holds true for most gases and in most conditions To study gases and their behavior then, is to assume that the gas is an “ideal” gas and follows all four gas laws (Boyle’s, Charles’, Gay-Lussac’s, & Avogadro’s)

6. Ideal Gases do not condense into a liquid at low temperatures do not have an attractive or repulsive force between particles is composed of particles that have no volume

7. Ideal Gas Law On those assumptions, we can combine the gas laws into one equation that gives us the relationship between all four variables: pressure temperature volume number of moles PV = nRT

8. Ideal Gas Law PV = nRT P = pressure V = volume n = number of moles R = proportionality constant T = temperature

9. The Proportionality Constant If units of kilopascals and Liters are used, the value of R is: 8.314 L  kPa ---------------------- mol  K

10. The Proportionality Constant If pressure is given in atm (instead of kPa): 0.0821 L  atm ---------------------- mol  K

11. Ideal Gas Law this relationship and formula describes the behavior of gases very well at room temperature and atmospheric pressure as the volume of the gas decreases , however, the attraction of the particles make the volume less than the formula would predict at extremely high pressures , the volume of the particles themselves is close to the total volume so the formula will predict a lower volume than what actually exists

12. Deviation of Real Gases from Ideal Behavior

13. Practice Using Ideal Gas Law pg 435 # 1 - 4