# CHEM&121 Exam 3: Chapter 7

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1. Properties of Gases
• A gas consists of particles - atoms/molecules - that move randomly & rapidly.
• The size of the particles are small compared to the space between them.
• Because the space is large, there are no attractive forces between them.
• The kinetic energy increases with increasing temp.
• When gas particle collide, they rebound. When they hit a wall, they exert pressure.
2. Gas Pressure
• Pressure (P) is the force (F) exerted per unit area (A).
• 1 atm = 760 mmHg = 760 torr = 14.7 psi = 101,325 Pa
3. Boyle's Law
• Pressure and Volume
• For a fixed amount of gas at constant temperature, the pressure and volume of a gas are INVERSELY related (when one increases, the other decreases).
• The same number of gas particles occupies 1/2 the volume and exerts 2X the pressure.
• Equation: P1V1=P2V2
4. Charles's Law
• Volume and Temperature
• For a fixed amount of gas at constant pressure, the volume of a gas is PROPORTIONAL to its Kelvin temp (if one increases, the other will also).
• Equation for C to K: C + 273
• Equation
5. Gay-Lussac's Law
• Pressure and Temperature
• For a fixed amount of gas at constant volume, the pressure of a gas is PROPORTIONAL to its Kelvin temp (if one increases, the other will also).
• Equation
6. Combined Gas Law
• Shows the relationship of Pressure, Volume, and Temperature for a constant number of moles.
• Equation
• Volume and Moles
• When the pressure and temperature are held constant, the volume of a gas is PROPORTIONAL to the number of moles present (when one increases, the other will also).
• Equation:
8. STP Conditions
• Pressure: 1 atm (760 mmHg)
• Temp: 273 K (0 degrees C)
• 1 mole of any gas has the same volume as 22.4 L (Standard Molar Volume).
9. Ideal Gas Law
• Pressure, Volume, Temp, Universal gas Constant (R), and Moles
• Equation: PV=nRT
• R=0.0821
10. Dalton's Law & Partial Pressures
• The total pressure (Ptotal) of a gas mixture is the sum of the partial pressures of its component gas.
• Equation for Total: Ptotal = A + B + C
• Equation for Partial: % of Gas = Decimal, THEN Decimal x Ptotal = Partial Pressure
11. London Dispersion Forces
• Weakest of all the intermoleculars due to momentary changes in electron density in a molecule.
• Includes all molecules and atoms
• The larger the molecule, the larger the attractive force between two molecules and the stronger the intermolecular force.
• Examples: CH4, H2CO, H2O
12. Dipole-Dipole Force
• Strongest after Dispersion.
• Attractive forces between TWO POLAR molecules.
• Examples: H2CO, H2O
13. Hydrogen Bonding
• Strongest after Dipole-Dipole
• Molecules containing H bonded to F, O, or N
• Examples: H2O
14. Ion-Dipole Force
• Strongest out of all the intermolecular forces.
• Mixtures of ionic compounds and polar compounds.
15. Boiling Point
• The temperature at which a liquid is converted to a gas phase.
• The increase in strength of the intermolecular forces, the increase in boiling points.
• Endothermic: energy is absorbed
• I.e. Hydrogen Bonding (H2O) would have a HIGHER boiling point than London Dispersion (CH4)
16. Melting Point
• The temperature at which a solid is converted to a liquid phase.
• The increase in strength of the intermolecular forces, the increase in melting points.
• Endothermic: energy is absorbed.
 Author: tgherasim ID: 297117 Card Set: CHEM&121 Exam 3: Chapter 7 Updated: 2015-02-28 22:55:07 Tags: chemistry Folders: Description: chapter 6 Show Answers: