CHEM 121 FINAL EXAM | UPDATED QUESTIONS AND ANSWERS UPDATED .Buy Quality Materials!
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Course
CHEM 121
Institution
CHEM 121
CHEM 121 FINAL EXAM | UPDATED QUESTIONS AND ANSWERS UPDATED .Buy Quality Materials!
Process to calculate the partial pressure of a gas in a mixture
Pgas = Xgas x Ptot
Dalton's Law
How to calculate mole fraction (Xgas) from mole percentage?
Xgas = Mole% / 100
Equation to calculate average ...
CHEM 121 FINAL EXAM | UPDATED QUESTIONS AND
ANSWERS UPDATED .Buy Quality Materials!
Process to calculate the partial pressure of a gas in a mixture
Pgas = Xgas x Ptot
Dalton's Law
How to calculate mole fraction (Xgas) from mole percentage?
Xgas = Mole% / 100
Equation to calculate average molecular mass of a gas mixture?
Average molecular mass=
∑(Xi×Mi)/∑Xi
Process of calculating mass percent of an element in a compound
Mass % = (mass of element in compound/ total mass of compound) x 100
Equation to relate the density of a gas to its molar mass
D = PxMW/RT
Formula to find the mass required when considering yield in a chemical reaction
Mass required = theoretical mass/yield
How to find the final total pressure?
1. convert all pressures to the same unit
2. use ideal gas law to find moles of each gas
3. calculate total volume
4. calculate final total pressure using:
Ptot = ((P1xV1)+(P2xV2)...)/Vtot
Average molecular mass calculation
1. Determine molar mass of each gas
2. Calculate the mole fraction of each gas
3. Multiply the mole fraction of each gas by its molar mass
4. Sum the products
root mean square (rms) velocity
a measure of gas speed used to calculate the kinetic energy of a gas
Urms = sqrt(3RT/M)
M = molar mass in kg/mol
R= ideal gas constant (8.314)
, T= temp in K
Law of Effusion
Rate 1/rate 2= sqrt(M2/M1)
greenhouse effect
Gases in the atmosphere that absorb infrared energy and trap it. It helps keep the
planet warm enough to support life.
ex. CO2, H2O, methane
760torr = ?cm
x100 cm
ex. 760 torr - 17 cm = 590 torr
Law of conversation of energy
Energy cannot be created or destroyed
Julius Robert Mayer
law of conservation of mass
Matter is not created nor destroyed in any chemical or physical change
Lavoisier
Dalton's Atomic Theory
1) elements are composed of atoms.
2) atoms of same element are identical, but differ from other elements.
3) elements can mix together
4) atoms only change when mixed with other elements
JJ Thompson's experiment
Watched deflection of charges in a cathode ray tube and theorized about + and -
charges in atoms. Guessed they looked like plum pudding
Millikan contributions
determined the charge of an electron was -1.60x10^-19 C
3 types of radiation
alpha particles, beta particles, gamma rays
Rutherford Experiment and Result
Gold foil experiment, atom is mostly empty space but massive positive center
isotopes
Atoms of the same element that have different numbers of neutrons
different types of bonds
covalent, ionic, hydrogen
Ammonium
NH4+
Nitrite
NO2-
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