Chem 122 General Chemistry II

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Chem 122 General Chemistry II

• Instructor Spencer Anthony-Cahill
• Office CB440
• Office hrs TBA
• e-mail sacahill_at_chem.wwu.edu
• http//atom.chem.wwu.edu/sacahill/122

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Chem 122 General Chemistry

• Lecture MTRF 11-1150am in SL 140.
• Ebbing and Gammon 8th Ed
• Lab W 11-150pm or R 2-450pm
• Pass safety quiz ASAP
• Get Lab Manual online
• Get safety goggles
• First lab meeting 4/11 or 4/12
• NO SANDALS/SHORTS/beach wear in lab.

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Chem 122 Exams/Grading

• 529 points possible
• two midterms _at_ 100 pts each
• Cumulative Final exam _at_ 150 pts
• 3 online homework assignments (83 pt total)
• Labs (8 12 pt each 96 pt total)
• Grade on a curve (if necessary) where median
  grade is C/C

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P force experienced over a surface due to
collisions between surface and gas particles
P hgd
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Boyles Law when Temperature is constant PV
constant or P constant 1/ V
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Charles Law when pressure is constant V
constant T or V/T constant
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Boyles Law PV constant
Charles Law V constant T
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• Ideal Gas assumptions
• No attractive or repulsive interactions between
  particles
• Volume of particles is negligible

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What is the pressure in system B vs. system A
assuming V T are constant? What is volume of
system C vs. system A assuming P T are constant?
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The Ideal Gas Law PV nRT
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Problem solving using PV nRT

• When mixed with Fe2O3, how much NaN3 is required
  to fill a 90 L airbag with N2 gas at 25 C and
  760 mm Hg?
• 6NaN3 (s) Fe2O3 (s) ? 3Na2O (s) 9N2 (g)

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To a first approximation (i.e., assuming ideal
behavior), the TOTAL pressure in a vessel is
equal to the sum of the partial pressures for
each gas in the vessel.
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Online HW 1 Question 10

• You have a sealed 1.52 L container  with a
  mixture of nitrogen and helium gas.  If the gas
  mixture contains 0.345 atm of nitrogen, and 0.731
  g of helium.  Calculate the mole fraction of
  helium in the container at 24.5 oC.
• 0.412
• 0.895
• 0.830
• 2.93
• 0.947
• 0.845
• 0.690
• 0.345

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Problem solving using PV nRTand Daltons law
of partial pressures

• Problem 5.81
• If 3.85 L CO (g) was collected over water at 25
  C, how many grams of HCHO2 are consumed by
• HCHO2 (l) ? H2O (l) CO (g)

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What is the density of dry air at 30 ºC and 766.8
mmHg?
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The mean velocity of particles in a system
increases as the temperature of the system
increases
As temperature increases the proportion of higher
energy particles increasesThe temperature of
the system changes as a result of adding energy
to, or removing energy from, the system
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http//intro.chem.okstate.edu/1314F00/Laboratory/G
LP.htm
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Distribution of particle speeds for a single gas
at various temperatures
RMS speeds at 25 C (in meters/second)
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Calculations of RMS speeds of gases

• RMS speed u (3RT/Mm)1/2
• If R 8.31 (kg m2)/(s2 mol K) is used and molar
  mass (Mm) is input units of kg/mol, the units of
  u will be m/s.
• Exercise 5.13 (p 205) At what temperature do H2
  molecules have the same RMS speed as N2 at 455
  ºC? At what temperature do H2 molecules have the
  same kinetic energy as N2 at 455 ºC?

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Diffusion takes time because the motion of
particles is CHAOTIC
like an energetic dog on a hike.
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Effusion is proportional to RMS speed. When P
T are held constant the rate of effusion is
proportional to (1/Mm)1/2 where Mm molar mass
of the gas
A lighter molecule collides more frequently with
the container thus, it will effuse faster than a
heavier one.This is the basis for the
enrichment of uranium (for nuclear reactors)
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Real gases do experience intermolecular
attractions and do occupy volume (these factors
are ignored for ideal gases)
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Real gases do experience intermolecular
attractions and do occupy volume (these factors
are ignored for ideal gases)
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