Gases

Question 1

macroscopic level of gases

Answer 1

properties

Question 2

molecular level of gases

Answer 2

• structure
• dynamics (motion)
• intermolecular forces

Question 3

equation and definition for pressure

Answer 3

P=F/A
= force exerted per area

Question 4

SI units for pressure

Answer 4

Pa = N/m^2
kPa=10^3 Pa

Question 5

1atm =

Answer 5

101.3 kPa, 760mmHg (Torr)

Question 6

1 bar =

Answer 6

100.0 kPa

Question 7

equation for pressure with density, g, and h

Answer 7

p x h x g, where g = 9.8m/s^2

Question 8

what does the manometer lead to?

Answer 8

an equalisation of pressure:
P(atm) = P(Hg) = p(Hg)gh(Hg)

Question 9

if the Hg in a manometer was replaced with water, would the height of the water be greater or less than Hg?

Answer 9

greater, due to water’s lower density (P constant, p goes down, g constant, so h goes up)

Question 10

describe kinetic molecular theory - the ideal gas

Answer 10

1. gases made of tiny particles moving completely randomly
2. total volume of particles very small compared to size of container
3. particles do not interact with each other
4. particle collisions are elastic (no energy lost)
5. kinetic energy (KE) increases with temperature

Question 11

describe (5) KE increases with temperature

Answer 11

for a large collection of molecules:
- at a given temperature, all gases have the same distribution of kinetic energy
- each molecule: KE = 1/2mv^2

Question 12

what is the effect of temperature on average kinetic energy?

Answer 12

the average kinetic energy increases with temperature

Question 13

state 2 equations relating kinetic energy with temperature

Answer 13

KE(avg) = 3RT/2
Temperature is in Kelvin
KE is in J/mol

KE (avg) = 3RT/2Na
for a single gas molecule

Question 14

units for R

Answer 14

J/molK

Question 15

3RT/2Na =

Answer 15

1/2mu^2

Question 16

state the 2 equations relating u, R, T, m, Na, and M

Question 17

how is kinetic energy dependent on the mass of the particles?

Answer 17

at the same temperature, more massive molecules move slower

Question 18

what does pressure result from?

Answer 18

gas particles colliding with container walls

Question 19

Boyle’s law

Answer 19

at constant T and fixed n, volume is inversely proportional to pressure, or V=k/P

Question 20

low Pext = Pgas

Answer 20

-> high V

Question 21

high Pext = Pgas

Answer 21

-> low V

Question 22

Charles Law

Answer 22

at same P and fixed n, volume is proportional to temperature, or V= kT

Question 23

Avogadro’s law

Answer 23

V=kn

Question 24

what equation describes an ideal gas?

Answer 24

PV = nRT
P - atm
V - L
T - K

Question 25

P1V1/n1T1 =

Answer 25

P2V2/n2T2

Question 26

mole fraction of gas A

Answer 26

Xa = na/ntotal = Pa/Ptotal

Question 27

law of partial pressures

Answer 27

Pa + Pb + Pc +.... = PTotal PA = XA × Ptotal

Question 28

define effusion

Answer 28

escape of a pas through a hole into a vacuum

Question 29

define diffusion

Answer 29

movement of one gas through another

Question 30

how does a barometer work?

Answer 30

The mercury column in the mercury barometer stays up due to the force exerted by the atmosphere on the mercury in the outer reservoir just balancing the gravitational force on the mercury in the tube. Its height adjusts according to the air pressure on the reservoir. The column of mercury is shorter on a mountaintop as there is less atmosphere to exert a force on the mercury reservoir. On a mountaintop, the air pressure is less, so the height of mercury it balances in the barometer is shorter than at sea level where there is more air pressure