15) ideal gases Flashcards
What is Avagadro’s constant?
A number of particles equal to the number of atoms in 12 grams of carbon-12
What is one mole of a substance?
An amount in which the number of atoms/molecules is equal to Avogadro’s constant.
How do you find the mass of one atom from its nucleon number?
Multiply nucleon number by the atomic mass unit (u) in kg.
How is the atomic mass unit defined?
It is 1/12th the mass of a Carbon-12 atom
How do you calculate the number of particles from the number of moles of a substance?
Number of particles = number of moles × Avagadro’s constant
How do you find the molar mass of a substance from the molecular mass?
Molar mass = Molecular mass x Avagadro’s Number
How do you find the total mass of a substance from the number of moles?
number of moles x molar mass
How do you calculate the number of moles of a substance from the number of particles?
Number of particles÷Avagadro’s number
How do you find the molar mass of an element from its nucleon number?
Molar mass is equal to nucleon number in grams.
Boyle’s law: Pressure is inversely proportional to…
Volume for a fixed mass of gas at constant temperature
Charles’ law: Volume is proportional to…
Absolute temperature for a fixed mass of gas at constant pressure.
Gay Lassac’s Law: Pressure is proportional to…
Absolute temperature for a fixed mass of gas at constant volume
Avogadro’s law: Volume occupied by a gas is proportional to…
Number of particles/moles if pressure and temperature are constant.
How do you find absolute zero from a pressure temperature graph?
Extrapolate the line to find the x-intercept.
What is R in pV = nRT?
Molar Gas Constant (8.31)
What is N in pV = NkT?
Number of particles
What is n in pV = nRT?
Number of moles
What is k in pV = NkT?
Boltzmann constant
What units of temperature should be used in the ideal gas equation?
Kelvin
What is the equation of state for an ideal gas?
pV = NkT OR pV = nRT
What is an ideal gas?
A theoretical gas that obeys the gas laws at all pressures and temperatures
What are the SI units of pressure?
Pascal (Pa or Nm⁻²)
What is the definition of pressure?
The force per unit area exerted normally to a surface
What is the relationship between root mean square speed of particles in a gas and absolute temperature?
rms speed is proportional √(absolute temperature)
Why does increasing the temperature of an ideal gas increase pressure?
Particles have greater kinetic energy so there is a greater rate of collisions and greater change in momentum per collision.
Why does increasing the volume of an ideal gas decreases pressure?
P=F/A. Force exerted decreases as the rate of collisions with the container decreases and the surface area increases.
According to Newton’s second law if a particle experiences a change in momentum…
There must be a force acting on the particle.
According to Newton’s third law if a container exerts a force on a particle…
The particle must exert a force on the container.
How do you calculate the mean square speed of gas particles from their velocity?
Square the magnitude of the velocity of each individual gas molecule and then take the average of these values.
How do you calculate root mean square speed of a gas?
Square the magnitude of the velocity of each individual gas molecule, take the average of these values and then take the square root.
Why is root mean square speed used instead of velocity?
Average velocity is zero.
What is N in pV = ¹/₃ N m (c)²
Number of particles
What is (c)² in pV = ¹/₃ N m (c)²
Mean square speed
What is ³/₂kT equal to?
The mean kinetic energy of a gas particle
What form is the internal energy of an ideal gas?
Purely kinetic (i.e. no potential energy)
Why is there no potential energy in an ideal gas?
Because there are no force between particles (except during collisions).
What is ³/₂NkT equal to?
Total internal energy of an ideal gas.
Kinetic theory assumption concerning volume
The volume of the particles in a gas is negligible compared to the volume of the container
Kinetic theory assumption concerning forces
There are no electrostatic forces between particles except during collisions
Kinetic theory assumption concerning motion
Particles are in continuous, rapid, random motion.
Kinetic theory assumption concerning collisions
The collisions particles undergo with each other and the container are all elastic
Kinetic theory assumption concerning time
The duration of collisions is negligible compared to the time between collisions
What is the relationship between absolute temperature and the average KE of particles in a substance?
Absolute temperature is proportional to average kinetic energy of the particles in a substance.
