Chapter 15, The Kinetic Theory of Gases Flashcards
Equation for number of molecules in a substance?
N = n * N_A (Number of molecules = number of moles * Avogadro’s constant).
Equation for molar mass?
m = n * M (mass = number of moles * molar mass, molar mass is the mass of one mole of a substance).
What are the assumptions made for the kinetic model of an ideal gas?
The gas contains a large number of molecules moving at random at different speeds.
The molecules volume is negligible compared to that of the container.
Collisions between molecules is perfectly elastic.
The time of a collision is negligible compared to the time between collisions.
Electrostatic forces are negligible except during collisions.
What is Boyle’s Law?
Pressure (p) is inversely proportional to volume.
What experiment can be done to show Boyle’s law?
Use a volume scale (looks like a thermometer but markings show volume) which has oil at the bottom (oil changes very little under pressure), use a pump to force more air into the volume scale and use a pressure gauge to measure the pressure. Then plot a graph of p against 1/V and you should get a straight line.
What is Charles’ law?
Volume (V) is directly proportional to temperature (T).
What is the relationship between pressure and temperature?
Pressure (p) is directly proportional to temperature (T).
How can the relationship between pressure and temperature be measured?
Put a container of gas and some water in a container with a thermometer, connect the gas container to a pressure gauge and slowly heat the water then take readings from the thermometer and pressure gauge.
How can an experiment on the relationship between pressure and temperature be used to find a value for absolute zero?
Since p ∝ T is only true if you use the Kelvin temperature scale, plotting a graph of p against T and extrapolating to find the T intercept will give a value for absolute zero.
What does the equation pV/T = nR show?
Pressure * volume / Temperature = mole number * molar gas constant ( ≈ 8.31 J / K / mol) for an ideal gas.
What is r.m.s.?
Root mean square speed, find the square root of the mean of the squares of all the velocities of particles in a gas.
What does the equation pV = Nmc^2(bar).
Pressure * volume = number of particles * mass of particles * mean square speed.
What is the distribution of particles in a gas?
Maxwell-Boltzmann distribution, (like a normal that’s been squished to the left).
Where does the r.m.s. value lie relative to the mean and most probable speed on a Boltzmann distribution?
The most probable speed is the peak, the mean lies to the right of it and the r.m.s. is right of the mean.
How do you work out the Boltzmann constant k?
k = R /(N_A) (Boltzmann constant = Molar gas constant / Avogadro’s constant).
