Gases

Question 1

Gas Laws

Interaction of External and Internal Pressure

Answer 1

• No change: Internal Pressure = External Pressure
• Compression: Internal Pressure < External Pressure
• Expansion: Internal Pressure > External Pressure

Question 2

Gas Laws

Calculating Pressure under liquid

Equations

Answer 2

• With Atmosphere: P(H2O)[“Column Pressure”] + P(atm)[atmospheric/ barometric pressure]
• In Vaccum: P(H2O)[“Column Pressure”]

Question 3

Properties of Gases

What is a Vapor?

Answer 3

• Gaseous state of substance usually a liquid or solid at room temp and pressure

Question 4

Properties of Gases

Gas Elements

that are gases at Room Temp

Answer 4

• Noble gases(are isolated atoms)
• Diatomic Gases: H2, N2, F2, O2 and Cl2
• HCl, NH3, CO2, N2O, CH4, HCN

Question 5

Gas Characteristics

Gas Characteristics

Answer 5

1. Gases assume shape and volume of container
2. Move in constant, random motion but in straight line
3. Gas Density less than Liquid Density or Solid Density
   
   • It is highly variable[*Increased T –> Decreased D vs Increased P –> Increased D] *
4. Gases form Homogeneous Mixture with each other in any proportion [0 rxn = mutually miscible]

Question 6

Pressure

Pressure equation

Answer 6

• F/a
• dgh[in Pascals]
• mmHg is a measure as well as a pressure unit

Question 7

Monometer

What is a Monometer

Answer 7

• Measures gas P
• P = difference of liquid height
• 2 types
  1. Close-end(vaccum)
  2. Open-end(atm)

Question 8

Pressure

Conversions

Answer 8

1 atm = 760 mmHg = 760 Torr = 101.325 kPa = 1.0325 bar = 14.7 lb/in^2 = 101,325 N/m^2

Question 9

Monometer

Monometer Equations

Answer 9

• For Close-Ended: Pgas = Δh(liquid)
• For Open Ended:
  1. Pgas = Δh(liquid) + Patm[Pgas>Patm]
  2. Pgas = Δh(liquid) - Patm[Pgas<Patm]

Question 10

Ideal Gas Law Equation

What is STP?

Answer 10

• Standard Temperature and Pressure
• 273.15 K and 1 atm

Question 11

Ideal Gas Law Equation

What is an Ideal Gas?

Answer 11

• @ higher Temperature: More gases
• @ Lower pressure: More space
• Rules:
  1. Gases move randomly
  2. No attraction between particles
  3. “Infinite” volume and and Volume of gas not important
  4. Obeys simple gas laws: Boyle, Charles, Avagadro

MCQ?

Question 12

Ideal Gas Law Equation

Boyle, Charles, Avagadro Equations

Answer 12

• Boyle: V=1/P
• Charles: V=T
• Avagadro: V=n

MCQ?

Question 13

Ideal Gas Law Equation

Combined Gas Law

Answer 13

P1xV1/(n1xT1)=P2xV2/(n2xT2)

Question 14

Ideal Gas Law Equation

Units

Answer 14

• P = any
• V = any
• n= mol
• T = K

Question 15

Ideal Gas Law Equation

Types of R

Answer 15

• R = 0.08206 liter·atm/mol·K
• R = 62.36 L·Torr/mol·K or L·mmHg/mol·K

Question 16

Density equation

Answer 16

D=MP/RT

Question 17

Molarity Equation

Answer 17

M=mRT/(PV)=DRT/P

Question 18

Stoichiometry with Gases

Law of Combining Gas Volumes

Answer 18

• Ratios from balanced equations can be in L instead of mol when Same Temp and P
• If not use ideal gas law as part of stoic(Ex. 1/P to get rid/add Pressure)

Question 19

Dalton’s Law of Partial Pressure

Equation for P.P.

Answer 19

• Ptot=P1+P2+…Pi

Question 20

Mole Fractions of Gases

Equations

Answer 20

• Xi=ni/ntot=Pi/Ptot
• Mole % = Mole Fraction * 100%

Question 21

Kinetic Energy Molecular Theory

Postulates

Answer 21

1. Gas particles so small and distance so large that individual volume is negligible
2. Particles in Constant Motion
3. No Forces between Particles(No Attraction or Repulsion)
4. Average Ke proportional to T(in K)

Question 22

Kinetic Energy Molecular Theory

Deviation of Ideal Gas Law Equation

Answer 22

• P=1/3(N/V)mū^2
• N= # of molecules
• m = mass of 1 mole
• ū^2 = Average of squared velocities

Question 23

Kinetic Energy Molecular Theory

Proportions

Answer 23

• KE proportional to T
• Urms proportional to √1/M
• Urms proportional to √T

Question 24

Kinetic Energy Molecular Theory

Equalities

Answer 24

• U1/U2 = √(M2/M1)
• t1/t2 = √(M1/M2)

Question 25

Kinetic Energy Molecular Theory

Root Mean Square Velocity Equation

Answer 25

• √(ū^2) = √(3RT/M)
  1. R = 8.314 J/(mol·K)
  2. M= kg/mol
• OR sum of speeds squared divided by number of molecules, then sqrted

Question 26

Kinetic Energy Molecular Theory

What does Volatile mean?

Answer 26

• Molecules that have weaker IMFS; easier to go from liquid to gas

Question 27

Kinetic Energy Molecular Theory

What does Effusion Mean?

Answer 27

• Gas escapes container through hole into an evacuated chamber
• Diffusion Properties still in play(Go from high to low pressure)
• Effusion inversely proportional to √M

Question 28

Non-Ideal Gas Behavior

When does Non-Ideal Gas Behavior happen?

Answer 28

• Low Temp, High Pressure
• As Temp increases, deviation decreases: Less IMFs because of less interaction
• As Pressure increases, deviation increases: Actual volume available will be greater than predicted because gas molecules take up more space

Question 29

Non-Ideal Gas Behavior

Van der Waals Equation

Answer 29

• P=nRT/(V-nb) - (n^2)(a)/(V^2)
  1. a and b gas constants
  2. nb = accounting for size of gas molecules
  3. n^2a = accounting for IMFs