gaseous state

Question 1

state avogadros law and formula

Answer 1

for a gas at constant temperature and pressure,
v1/n1 = v2/n2

Question 2

state gay-lussacs law and formula

Answer 2

for a fixed mass of gas at constant volume, the
p1/t1=p2/t2

Question 3

state charles law and formula

Answer 3

at constant pressure and fixed mass, v1/t1 = v2/t2

Question 4

boyles law and formula

Answer 4

for a fixed mass of gas at constant temperature
p1v1 = p2v2

Question 5

explain ideal gas equation

Answer 5

pV = nRT
p in Pa or Nm-2
V in m3
n in mol
T in Kelvin

Question 6

using ideal gas eqn to determine molar mass

Answer 6

M = mRT/pV
M in g mol-1
m in g

Question 7

using ideal gas eqn to determine density of a gas

Answer 7

density = m/v = pM/RT

Question 8

assumptions of ideal gas

Answer 8

1. gas particles have negligible volume
2. gas particles exert negligible attractive forces on one another

Question 9

how does a gas approach ideality at low pressure and high temperature

Answer 9

low pressure:
gas particles very far apart, volume occupied by gas particles negligible compared to volume of container
intramolecular attractive forces between widely spaced gas particles are negligible

high temperature:
gas particles possess high enough kinetic energy to overcome intermolecular attractive forces
intermolecular attractive forces can be considered negligible

Question 10

how does a gas deviate from ideality

Answer 10

high pressure:
gas particles closer together, occupies smaller volume
vol of gas particles not negligible compared to vol of container
intermolecular attractive forces are significant

low temperature
gas particles posess less energy so intermolecular attractive forces are significant

Question 11

why is there negative deviation when moderately high pressure is exerted on the system

Answer 11

volume of system becomes smaller
gas particles come closer together
intermolecular attractive forces between gas particles become significant
gas occupies smaller volume than ideally
pv/rt < 1

Question 12

why is there positive deviation when very high pressure is exerted on the system

Answer 12

volume of the system becomes very small
gas particles very close together, repulsion between electron clouds present
gas particles experience intermolecular repulsive force
gas occupies volume larger than ideally
pv/rt > 1

Question 13

ranking of extent of deviation

Answer 13

deviation is greatest for polar molecules for strong intermolecular forces of attraction such as pd-pd and H bonding, and smallest for small non-polar molecules

Question 14

mole fraction

Answer 14

mole fraction = Xa = no of moles of a/total no of moles

Question 15

partial pressure

Answer 15

P of a = Xa times Ptotal

Question 16

what is evaporation

Answer 16

in a closed container,
some of the more energetic particles on hte surface of the liquid possess enough energy to escape from the attractive forces holding the liquid togther, evaporating

Question 17

vapour pressure

Answer 17

pressure exerted on the liquid surface and on the wall of the container by the gaseous particles that have evaporated and are trapped above the liquid

Question 18

saturated vapour pressure

Answer 18

at a certain temperature, number of particles evaporating = number of particles condensing so there is a fixed number of gaseous particles in the space above the liquid which exerts a vapour pressure, namely saturated vapour pressure

Question 19

relating intermolecular forces, boiling points and vapour pressures

Answer 19

stronger the intermolecular forces of a liquid, more difficult for its particles to escape from liquid surface so lower its volatility and saturated vapour pressure, but higher its boiling point