PHYSICAL CHEMISTRY FINAL EXAM- 1 REVISION QUESTIONS 2024/2025. THE
LATEST REVISION QUESTIONS AND CORRECT ANSWERS IN 2024/2025.
(ALREADY GRADED A+) (LATEST 2024 UPDATE)
What is EFFUSION - ANSWER- the escape of gas molecules from high pressure region to low
pressure region
GRAHAM'S LAW states that the rates of both EFFUSION and DIFFUSION are _____
proportional to the molecule's molar mass - ANSWER- INVERSELY PROPORTIONAL to
MOLAR MASS
rate(2)/rate(1) = sq root (M1/M2)
EFFUSION TIMES - ANSWER- time(1)/time(2) = rate(2)/rate(1) = sq root (M1/M2)
FOR EQUAL NUMBERS OF MOLES!
The PERFECT GAS LAW assumes that there are no _____ or _____ forces between molecules in
a gas - ANSWER- attractive or repulsive
*valid at relatively low pressure (<10 atm)
*at intermediate pressure (10-200 atm), attractive forces become more important
*at higher pressure (>300-400 atm), repulsive forces predominate
COMPRESSIBILITY (Z) is defined as - ANSWER- Z = Vm/VmPG = Vm/(RT/P) = PVm/RT
*the quantity of Z measures the amount of deviation from ideality
COMPRESSIBILITY VALUES (Z) - ANSWER- PVm/RT = 1: gas is behaving ideally
PVm/RT < 1: attractive forces predominate
PVm/RT > 1: repulsive forces predominate
*as temperature increases, gas usually exhibits more ideal behavior, regardless of pressure
VAN DER WAALS EQUATION - ANSWER- P= nRT/(V-nb) -a (n/V)^2
*VDW [a(n/v)^2] corrects for molecular attractions
*at high volume and low pressure, the perfect gas equation is used
*at low volume and high pressure, the van der waals equation gives better answers
*gases have their OWN van der waals parameters
, When Pext > Pvap:
When Pext = Pvap:
When Pext < Pvap: - ANSWER- -LIQUID
-LIQUID+GAS (boiling point, in equilibrium)
-GAS
The CRITICAL TEMPERATURE (Tc) is defined as - ANSWER- the highest temperature at
which a substance can be liquefied
The CRITICAL PRESSURE (Pc) is defined as - ANSWER- the pressure required to liquefy a
substance at Tc
How do you convert to Kelvin from degrees Celsius? - ANSWER- K= C + 273.15
The LITER is also interchangeable with what unit? - ANSWER- dm^3
What is an EXTENSIVE PROPERTY? - ANSWER- a property that is proportional to the
amount
What is an INTENSIVE PROPERTY? - ANSWER- a property that is independent of the
amount
What are DERIVED INTENSIVE PROPERTIES? - ANSWER- molar quantities
Define ATOMIC MASS UNIT (AMU) - ANSWER- 1 amu = 1/12 mass of 1 atom of 12C
= 1.6605 X 10^-24 g
= mass of proton = mass of neutron (approx.)
Define ATOMIC WEIGHT (AW) (aka Atomic Mass) - ANSWER- mass of an atom, in amu
Define MOLECULAR WEIGHT - ANSWER- the weight of the molecule, in amu.
the sum of the AW's of all atoms in the molecule
One MOLE is equal to how many particles? - ANSWER- 6.022 X 10^23
(also known as Avogadro's number)
One Dalton is equal to... - ANSWER- 1 g/mol
(Dalton is often abbreviated Da)
How do you convert from grams to moles? - ANSWER- n = m/M
How do you convert from moles to molecules? - ANSWER- n = N/NA
LATEST REVISION QUESTIONS AND CORRECT ANSWERS IN 2024/2025.
(ALREADY GRADED A+) (LATEST 2024 UPDATE)
What is EFFUSION - ANSWER- the escape of gas molecules from high pressure region to low
pressure region
GRAHAM'S LAW states that the rates of both EFFUSION and DIFFUSION are _____
proportional to the molecule's molar mass - ANSWER- INVERSELY PROPORTIONAL to
MOLAR MASS
rate(2)/rate(1) = sq root (M1/M2)
EFFUSION TIMES - ANSWER- time(1)/time(2) = rate(2)/rate(1) = sq root (M1/M2)
FOR EQUAL NUMBERS OF MOLES!
The PERFECT GAS LAW assumes that there are no _____ or _____ forces between molecules in
a gas - ANSWER- attractive or repulsive
*valid at relatively low pressure (<10 atm)
*at intermediate pressure (10-200 atm), attractive forces become more important
*at higher pressure (>300-400 atm), repulsive forces predominate
COMPRESSIBILITY (Z) is defined as - ANSWER- Z = Vm/VmPG = Vm/(RT/P) = PVm/RT
*the quantity of Z measures the amount of deviation from ideality
COMPRESSIBILITY VALUES (Z) - ANSWER- PVm/RT = 1: gas is behaving ideally
PVm/RT < 1: attractive forces predominate
PVm/RT > 1: repulsive forces predominate
*as temperature increases, gas usually exhibits more ideal behavior, regardless of pressure
VAN DER WAALS EQUATION - ANSWER- P= nRT/(V-nb) -a (n/V)^2
*VDW [a(n/v)^2] corrects for molecular attractions
*at high volume and low pressure, the perfect gas equation is used
*at low volume and high pressure, the van der waals equation gives better answers
*gases have their OWN van der waals parameters
, When Pext > Pvap:
When Pext = Pvap:
When Pext < Pvap: - ANSWER- -LIQUID
-LIQUID+GAS (boiling point, in equilibrium)
-GAS
The CRITICAL TEMPERATURE (Tc) is defined as - ANSWER- the highest temperature at
which a substance can be liquefied
The CRITICAL PRESSURE (Pc) is defined as - ANSWER- the pressure required to liquefy a
substance at Tc
How do you convert to Kelvin from degrees Celsius? - ANSWER- K= C + 273.15
The LITER is also interchangeable with what unit? - ANSWER- dm^3
What is an EXTENSIVE PROPERTY? - ANSWER- a property that is proportional to the
amount
What is an INTENSIVE PROPERTY? - ANSWER- a property that is independent of the
amount
What are DERIVED INTENSIVE PROPERTIES? - ANSWER- molar quantities
Define ATOMIC MASS UNIT (AMU) - ANSWER- 1 amu = 1/12 mass of 1 atom of 12C
= 1.6605 X 10^-24 g
= mass of proton = mass of neutron (approx.)
Define ATOMIC WEIGHT (AW) (aka Atomic Mass) - ANSWER- mass of an atom, in amu
Define MOLECULAR WEIGHT - ANSWER- the weight of the molecule, in amu.
the sum of the AW's of all atoms in the molecule
One MOLE is equal to how many particles? - ANSWER- 6.022 X 10^23
(also known as Avogadro's number)
One Dalton is equal to... - ANSWER- 1 g/mol
(Dalton is often abbreviated Da)
How do you convert from grams to moles? - ANSWER- n = m/M
How do you convert from moles to molecules? - ANSWER- n = N/NA
