CHEM 1B Study Guide - Final Guide: Boiling Point, Network Covalent Bonding, Supercritical Fluid
Chemistry 1B Final Study
Guide
Chapter 10 [11]: Gases
1. Pressure and its units
a. 1 atm=760 torr=760 mmHg=14.7 psi=101,325 Pa
b. P=force/area
c. P decreases as altitude increases
2. Manometer
a. U-shaped tube connected to a flask which holds the gas sample
b. If mercury on the left side (where atm pressure is) is higher, then the pressure of the gas sample
is greater than atm pressure
c. If mercury on the right side (where gas sample is) is higher, then the pressure of the gas sample
is less than atm pressure
d. If height of mercury is the same on both, the gas sample pressure=atm pressure
e. To find pressure, measure the height difference and convert cm to mm
3. Ideal Gas Law
a. Boyle’s Law-Volume and Pressure are inversely related: P1V1=P2V2
a.i. If you compress something, the molecules will hit each other and the wall more often so
pressure increases as volume decreases
b. Charles’ Law-Temperature and Volume are directly related: T1/V1=T2/V2
b.i. If you put a balloon in cold water, the molecules move slower and aren’t expanding the
balloon as much so volume decreases as temperature decreases
b.ii. density decreases as volume increases (T increases)warmer air rises because less dense
b.iii. T MUST BE IN KELVINS [T(K) = T(C) + 273.15]
c. Avogadro’s Law-Volume and moles are directly related: V1/n1=V2/n2
d. Gay Lussac’s Law-Temperature and Pressure are directly related: T1/P1=T2/P2
e. PV=nRT
e.i. R=gas constant=0.08206 Latm/Kmol
4. Gas Density
a. Density=m/V
b. From the ideal gas law: density=P(MW)/RT
b.i. PV=nRT
b.ii. n/V=P/RT (density is grams/L)
b.iii. n/V=P(MW)/RT (multiply by MW to convert mols to gram)
c. MW=dRT/P
5. STP
a. P=1 atm, T=0 degrees Celsius or 273.15 K
b. Standard ambient Temperature and Pressure (SATP): P=1 atm, T=25 degrees Celsius or 298.15
K
6. Molar Gas Volume
a. Volume occupied by 1 mol of a substance
b. PV=nRTV=(1 mol) (0.08206 Latm/Kmol)(273.15 K)/1 atm= 22.41 L
c. Molar volume at SATP=24.47
7. Partial Pressure in a Gas Mix
a. Dalton’s Law of Partial Pressure: the total pressure is equal to the sum of the partial pressures of
the individual gasPT=P1+P2+P3 (V and T are constant)
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b. Partial Pressure of gas: XAPT
b.i. XA=mol A/total mol
8. Kinetic Molecular Theory
a. A gas is a collection of particles in constant motion
b. Size of particles are negligibly small so they occupy no volume since the space between atoms is
very large
c. Particles undergo elastic collisions, exchanging energy but no overall loss in KE (energy of
motion); average KE is proportional to T
d. Lots of empty space b/w particles
e. Particles are constantly moving in random directions and with different speeds
f. Ideal gas have no attractions between gas molecules and molecules don’t take up space (small
volume)
9. Average Molecular Speed
a. T is the measure of the avg KE of particles
b. Average kinetic energy of molecules are the same but the average velocity of each molecule
differs with molar mass
b.i. To have the same kinetic energy with the heavier molecules, lighter molecules need to
move faster so that’s why speed differs for each molecule
b.ii. Lighter particles travel faster then heavier ones
b.iii. Average KE is the same because it is only temperature dependent
c. Urms=sqrt 3RT/MW
d. As T increases, average velocity or speed of particles increase
e. Mean Free Pathaverage distance that a molecule travels in between collisions
e.i. Inversely proportional to pressure
10. Diffusion and Effusion of Gases
a. Diffusiongradual mixing of gases as they move with the concentration gradient
b. Effusiongas under pressure moving out to another compartment through an opening
c. Rate 1/rate 2= sqrt MW2/MW1
d. Lighter molecules move faster
e. Rate is proportional to 1/sqrt MW
e.i. The smaller the rate, the smaller the denominator and the higher and faster the rate
11. Stoichiometric Calculations Involving Gaseous Reactants
a. Gas @ STP, use 1 mol=22.4 L, gas @ SATP, use 1 mol=24.47 L
b. @ other conditions, use ideal gas law
12. Deviations from the Ideal Gas Law and Van der Waals Equation
a. Ideal gas behavior breaks down under LOW T AND HIGH P
b. a is a correction for IMF
b.i. at low T, the IMF have more of an effect and collisions become more sticky
b.ii. real molecules attract each other when they are close so the molecules don’t collide with
walls as much, lowering the pressure
b.ii.1. P+a(n/v)2
b.ii.2. Larger parameter corresponds to stronger IMF
c. b is a correction for particle size
c.i. volume of a real gas is larger than predicted because real molecules take up space at high
P
c.ii. adjust volume of container minus the space that the particles themselves take up
c.ii.1. V-nb
c.ii.1.a. b is different for every gas
c.ii.2. Larger parameter=bulkier molecules
c.ii.3. Van der Waals equation: [P+a(n/v)2]*[V-nb]=nRT
d. Effect of b is greater than effect of a when weak IMF
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Chapter 11 [12]: Liquids, Solids, and IMF
1. Intermolecular and intramolecular forces
a. Intermolecular forces are forces between molecules; generally weaker b/c small charges
interacting at larger distances. Intramolecular forces hold atoms together in a molecule
b. IMF originate from the attractive force b/w electrostatic interactions between charged bits of
molecule. They also originate from repulsive forces that rise from electrostatic repulsion between
electrons.
b.i. PE decreases with increasing magnitude of charge and decreasing separation
c. Permanent dipole moment and ion-dipole forces
c.i. Ion-dipole force between an ion and polar molecule
c.i.1. Separation b/w ion and polar is large then weaker bindingsmaller cations
have stronger ion-dipole interactions
c.i.2. Charge on ion or dipole is large then stronger binding
c.ii. Permanent dipole moment-one positive end and one negative end on molecule=polar
c.iii. Hydration-water attaches to solute particles
c.iii.1. Smaller ions hydrate more easily because of stronger ion-dipole
c.iii.2. Greater charge ions hydrate more easily because of stronger ion-dipole
d. Molecular polarizability and induced dipole moment; dipole-dipole forces
d.i. Dipole-dipole forcewhen negative end of one polar molecule is attracted to positive end
of another polar molecule; electrostatic
d.ii. Induced dipole momentwhen a polar molecule induces a dipole in an unpolarized atom
d.iii. Polarizabilityextent to which the electron distribution in an atom or molecule can be
distorted by an external field
d.iii.1. Induced dipole=polarizability*electric field
d.iii.2. Increases with molecular size and greater electron cloud
e. Instantaneous dipole moment; London (dispersion) forces
e.i. Instantaneous dipole momenttemporary dipole cause by random movement of electrons
e.ii. London (dispersion) forcespresent in all molecules; attractive force from instantaneous
dipole induced by random fluctuations of electrons
e.ii.1. Increases with molecular size
f. Hydrogen bond
f.i. FON bonds with H-N, H-O, or H-F
f.ii. FON is acceptor and O, N, F-H is donor
f.iii. Strong dipole-dipole interaction
g. Strong IMF=high bp, mp, surface tension, viscosity; lower vapor pressure
g.i. BP increases with molecular weight b/c of higher dispersion forces
g.ii. Longer or more surface area molecules have more contact points so they have higher bp,
mp
h. Order in increasing strength: dispersion, dipole-induced dipole, ion induced dipole, dipole-
dipole, hydrogen bonding, ion-dipole, ionic
2. Unique properties of water
a. Solid state is less dense than liquid state
b. Molecules arranged in tetrahedral arrangements
c. Liquid at room T despite low MW
d. High BP, High Cs
3. Exothermic and endothermic phase state changes
a. Exothermic: Condensation, Deposition, Freezing (CDF)
b. Endothermic: Melting (fusion), Vaporization, Sublimation (MVS)
4. Heat of vaporization, fusion, sublimation, and of other phase state changes
a. Hvap=Hvapor-Hli quid; Hcondensation=-Hvap
b. Hfusion=Hliquid-Hsolid; Hfreezing=-Hfusion
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Document Summary
Chapter 10 [11]: gases: pressure and its units, 1 atm=760 torr=760 mmhg=14. 7 psi=101,325 pa, p=force/area, p decreases as altitude increases, manometer, u-shaped tube connected to a flask which holds the gas sample b. c. If mercury on the left side (where atm pressure is) is higher, then the pressure of the gas sample is greater than atm pressure. If mercury on the right side (where gas sample is) is higher, then the pressure of the gas sample is less than atm pressure. If height of mercury is the same on both, the gas sample pressure=atm pressure d: to find pressure, measure the height difference and convert cm to mm. Ideal gas law: boyle"s law-volume and pressure are inversely related: p1v1=p2v2 a. i. If you compress something, the molecules will hit each other and the wall more often so pressure increases as volume decreases: charles" law-temperature and volume are directly related: t1/v1=t2/v2 b. i.
