8. Gas Laws

Question 1

Know Boyle’s Law vs Charles’ Law vs Avogadro’s Law vs Gay-Lussac’s Law vs combined gas law vs Henry’s Law

Answer 1

PV vs V/T vs n/V vs P/T vs PV/T vs [A1]/P1 = [A2]/P2 = kH where kH=Henry’s constant (varies depending on type of gas). T = IN KELVIN

Question 2

What are the ideal gas conditions aka amptns of kinetic molecular theory?

Answer 2

no intermolecular forces or repulsions b/w gas molec, negligible vol of gas molec when compared to vol of container, collisions = perfectly elastic —> conservation of momentum and energy, gas molec are in continuous random motion, avg KE of gas molec = proportional to absolute temp of gas

Question 3

Real gas occupies less pressure than ideal gas do. Why?

Answer 3

B/c at moderately high pressure, low vol and low temp, real gases have intermolecular forces —> causes attraction to e/o —> lower pressure by gas against container —> modify P in ideal gas law eqn

Question 4

Real gas occupies more volume than ideal gas do. Why?

Answer 4

B/c at extremely high pressure, low vol and extremely low temp, the size of real gases is bigger than the distance between them —> real gas occupy physical space —> modify V in ideal gas law eqn. Ideal gases don’t occupy physical space

Question 5

What is the heat capacity formula?

Answer 5

c = (3/2)nR = Q/deltaT

Question 6

A smaller heat capacity means what?

Answer 6

It takes less energy to raise the temp so quickly

Question 7

Units for ideal gas constant R

Answer 7

0. 0821 L atm/mol K

8. 314 J/mol K

Question 8

Alternative units for Joules (J)

Answer 8

Newton meters, N*m

Question 9

STP vs standard conditions

Answer 9

O degree C = 273 K, 1 atm ONLY FOR GAS LAWS vs 25 degree C = 298 K, 1 atm, 1 M ONLY FOR FREE ENERGY/ENTHALPY/ENTROPY, ELECTROMOTIVE FORCE

Question 10

Van der Waals eqn of state. Know its formula

Answer 10

Accounts for deviations from ideality when a gas doesn’t follow ideal gas law

The formula is basically an advanced form of PV=nRT. a=attractive forces, b=vol of molec themselves (“big particles”)

Question 11

Dalton’s law of partial pressure says that total pressure is sum of pressure of individual components. How to find pressure of individ components?

Answer 11

P_A = P_Total*X_A (where X_A = mol A/mol gas_Total)

Question 12

Avg kinetic energy formula for gas laws

Answer 12

KE = 1/2mv^2 = 3/2kbT, where kb = Boltzmann constant of 1.38E-23 J/K
T = related to molecular momentum

Question 13

Root mean square speed

Answer 13

u = sqrt(3RT/M)

M=molar mass in kg/mol

Question 14

Graham’s PE of diffusion vs effusion

Answer 14

Gases distribute thru vol randomly vs gases under pressure in one box move thru an opening of another; rate of effusion = inv proportional to root of molec wt

Question 15

Raoults Law

Answer 15

P_A = X_A*standardP_A

States that ideal sln behavior = observed when solute/solute, solute/solvent and solvent/solvent interactions are all very similar

Question 16

Maxwell-Boltzmann distribution curve

Answer 16

X axis = molecule speed, y axis = number of molec, higher curve = slower, lower curve = faster

Question 17

Can fluids (ie. liq and gases) be compressed to zero volume?

Answer 17

Nope

Question 18

REMEMBER: when talking about pressure, FOCUS ON GASES, NOT LIQUIDS

Answer 18

FOCUS ON GASES, NOT LIQUIDS