CHEM 1214 Study Guide - Spring 2018, Comprehensive Midterm Notes - Zwitterion, Weak Base, Vapor Pressure
12 Oct 2018
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Department
Course
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CHEM 1214
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Chapter 10:
Properties of Gases
1. Neither definite shape nor volume
2. Exerts pressure on surroundings and uniformly fills any container
3. Mixes completely with other gases
4. Kinetic Molecular Theory:
1. Gas molecules have small volumes compared to container’s value
2. Gas molecules don’t interact with other gas molecules (attraction/repulsion doesn't
matter)
3. Gas molecules move randomly and constantly and collide with walls of container
4. Average kinetic energy is only effected by temperature
Molecular Motion
1. Faster molecules, higher temperature (and visa versa)
2. All motion stops at absolute zero (0 K)
3. 0 K = -273 C
4. 1 mol = 6.022 x 10^23 molecules
5. Individual molecule have a range of kinetic energies (speeds)
1. Heavier gases move slower than lighter ones (when under the same temperature)
2. Effusion (gas through a hole) or Diffusion (gas though another gas)
1. gases with lower molar masses effuse faster
6. Range of energies falls along the maxwell-boltzmann distribution curve (higher temperatures
equals more distribution; although area under the curve is always the same)
7. Average kinetic energy: KE= ½m x Urms^2
1. All populations of gas molecules at the same temperature have the same average
kinetic energy
2. When using Ekin=(3/2RT), makes sure Ekin is in J and R is 8.314
8. Root mean squared speed: Urms = sqr. root (3RT/M)
1. T in K, Molar Mass in Kg, R is 8.314
2. Means that a particle with the average kinetic energy has this speed
Gas Laws
1. Properties of gases that change: pressure, volume, temperature
2. Ideal Gas Law
1. PV=nRT
2. T must be in K, V must be in L, P must be in atm
3. R= .08206
3. Combined gas laws
1. V/T, P/T, PV/T
4. Quantities on same side of equal sign are inversely proportional, on opposite side are
directly proportional
5. Under conditions of high pressure and low temperature gases do not behave ideally (law is
only valid at standard temperature and pressure: STP; which is at 1 atm and 273 K or 0 C)
6. Van der Waals equation corrects for these limitations (Real Gas Law)
1. a and b in the equation are constants
2. a reflects the strength of the molecular forces
1. Bigger the dip in the graph, the greater the molecular forces
2. As molar mass increases, the sizes of the atoms increase and have more electrons.
As the imbalance in electron distribution increases (polarizability) with greater molar
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mass, the weak interactions between gas particles become stronger and the value of
a increases
3. b reflects the size of the molecules (volume taken up by the particles of a gas)
1. bigger the slope of the graph, the bigger the size of the molecules
Pressures of Gases
1. Manometer: used to measure pressure in container
2. Barometer: used to measure pressure in atmosphere
1. As you go up, pressure goes down
3. Pressure in a Balloon:
1. P= Force/Area (higher the pressure, smaller the balloon area gets)
4. Dalton’s Law of Partial Pressures
1. When gases are mixed together, the total pressure is equal to the sum of the individual
gas pressures (partial pressures)
2. Ptotal= P1 + P2 +…
3. Mole fraction (X)= N1/Ntotal
4. P1= X1 x Ptotal
5. Steps to find partial pressures:
1. Find moles N1, N2…
2. Find Ntotal by adding N1+N2…
3. Make ratios for mole fractions N1/Ntotal…
4. Ptotal= (Ntotal x RT)/ Vtotal
5. Solve P1= X1 x Ptotal for partial pressures
Densities of Gases
1. D= PM/RT
1. D is in g/L, T in K, P in atm, M is molar mass
2. To find Molar Mass:
1. M= gRT/ PV
Solubility of Gases
1. Henry’s Law
1. Determines concentration of a gas by relating the partial pressure of a gas above a
solution to the concentration of a gas dissolved in the solution
2. Cgas= Kh x Pgas
1. Cgas is the concentration of gas in the solution (dissolved gas)
2. Kh is Henry’s gas constant for that particular gas (its magnitude reflects solubility)
3. Pgas is the partial pressure of the gas above the solution
1. The higher the partial pressure of the gas, the more soluble
2. Changes in pressure above solution will effect the solubility concentration of gas in the
solution
1. More gas = more pressure = more collisions = more dissolving = concentration increase
3. Solubility goes up as pressure goes up or if volume goes down
4. Solubility goes down as temperature goes up (ex. warm soda)
Chapter 11:
Fractional Distillation
1. Method of separating a mixture based on boiling points
1. Small molecules boil at a lower temperature
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