Unit 2 Review: KMT & Gas Laws (C21)

Unit 2 Review: KMT & Gas Laws (C21)

Chemistry 21

Mole Concept & Gram-Mole Conversions

• A mole is 6.02 x 10²³ particles: also called "Avogadro's Number"

• Moles are used to count large numbers of tiny particles

• Atomic Mass (amu) = Molar Mass (g/mol) on the Periodic Table

• Molar Mass: # grams in 1 mole of an element (Unit: g/mol)

Multiple Choice

What is the molar mass of copper, Cu (#29)?

• 29.00 g/mol

• 29.00 amu

• 63.55 g/mol

• 63.55 amu

Multiple Choice

How many grams of copper are in 6.8 moles?

• .00231 grams

• 432 grams

• 197 grams

• .00508 grams

Kinetic Molecular Theory:

Describes gas particle behavior

• Gas particles move in constant straight line motion

• Gas particle collisions are elastic (no loss of energy)

• Gas particles average kinetic energy is proportional to KELVIN temperature (not degrees celsius!)

• Gas pressure arises from gas particles colliding with walls of container

Multiple Choice

What is gas pressure?

• gas particle average kinetic energy

• gas particles colliding with walls of container

• gas particles 3D space

• gas particles moving in constant, straight-line motion

Multiple Choice

What is gas temperature?

• gas particle average kinetic energy

• gas particles colliding with walls of container

• gas particles 3D space

• gas particles moving in constant, straight-line motion

Multiple Choice

What is the relationship between pressure & temperature and why?

• Directly Proportional: particles collide with walls more frequently at higher speeds

• Inversely Proportional: particles collide with walls more frequently at higher speeds

• Directly Proportional: particles collide with walls less frequently at higher speeds

• Inversely Proportional: particles collide with walls less frequently at higher speeds

Multiple Choice

What is the relationship between pressure & number of particles and why?

• Directly Proportional: particles collide with walls more frequently at higher speeds

• Inversely Proportional: particles collide with walls more frequently at higher speeds

• Directly Proportional: more particles present causes more collisions with walls of container

• Inversely Proportional: more particles present causes more collisions with walls of container

Multiple Choice

What is the relationship between pressure & volume and why?

• Directly Proportional: particles collide with walls more frequently in a smaller volume

• Inversely Proportional: particles collide with walls more frequently in a smaller volume

• Directly Proportional: more particles present causes more collisions with walls of container

• Inversely Proportional: more particles present causes more collisions with walls of container

Combined Gas Law

• Combines P, V, n, & T into one equation

• Pressure & Volume Units: must match for initial and final conditions

• Number of Particles (n) Units: moles

• Temperature Units: Can only be KELVIN temperature!

Multiple Choice

2.00 moles of a gas sample have a volume of 6.00 L. What would the new volume be to accommodate 4.00 moles at the same temperature and pressure?

• 6.00 L

• 3.00 L

• 4.00 L

• 12.00 L

Multiple Choice

A sample of gas at 80^oC has a pressure of 68 kPa. What will the new pressure be if the temperature is decreased to 40^oC?

• 34 kPa

• 136 kPa

• 60.3 kPa

• 76.7 kPa

Multiple Choice

0.75 moles of gas at 200K has a pressure of 900 mmHg. How many moles would be required to have a pressure of 700 mmHg and a temperature of 100K?

• 0.83 moles

• 1.2 moles

• 0.375 moles

• 1.5 moles

Ideal Gas Law

• Used to calculate P, V, n, or T for a gas sample at ONE condition

• R is a gas constant

• Pressure in atmospheres

• Volume in liters

• Number of Particles (n) in moles

• Temperature in Kelvin

Multiple Choice

What is the volume of 2.5 moles of gas with a pressure of 600 mmHg at a temperature of 100^oC?

• 0.0103 L

• 96.9 L

• 0.0342 L

• 29.2 L

Multiple Choice

At what temperature will you have to have 26 grams of Xe gas in a 0.5 L container with a pressure of 3.5 atm? (Hint: The molar mass of Xe is 131 g/mol.)

• 108 K

• 503 K

• 821 K

• 122 K