2B6 Kinetic Molecular Theory Flashcards
Explain the kinetic molecular theory, the behavior of ideal gases, and different gas laws.
What does the Kinetic Molecular Theory (KMT) primarily describe?
The behavior of particles, especially gases.
KMT can also be applied to solids and liquids.
The KMT of gases is a set of rules describing the behavior of gas molecules in motion.
Define:
Kinetic Molecular Theory
Matter is made of invisible moving particles in constant random motion, colliding elastically.
This theory assumes gas particles exert no attractive force on each other.
How are molecules arranged in a solid according to KMT?
Tightly packed, swaying in place without changing location.
Solids are not affected by the shape or volume of their container.
What distinguishes liquid molecules from solid molecules in KMT?
Liquid molecules have more space between them and move faster than solid molecules.
Liquids take the shape of their container but not the volume.
How do gas molecules behave differently from solid and liquid molecules?
Gas molecules:
- Are farthest apart.
- Move the fastest.
- Take both the shape and volume of their container.
They can overcome attractive forces that hold them together.
They have the highest KE.
List the basic assumptions of the Kinetic Molecular Theory.
- Gas molecules are in random, constant motion.
- Particles move in straight lines until collisions occur.
- There is no force of attraction between gas molecules.
- Most of the volume of a gas is empty space.
- Collisions between gas molecules are perfectly elastic.
- Average kinetic energy is proportional to temperature.
How does temperature affect tire pressure according to KMT?
- Cold temperatures: Decrease molecular movement lowering air pressure.
- Hot temperatures: Increase molecular movement increasing air pressure.
This demonstrates KMT in everyday life.
What is Dalton’s Law of Partial Pressure?
The pressures of all the gases in a mixture add up to the total pressure of the gas solution.
This law is fundamental in understanding gas behavior in mixtures.
Partial pressure is the pressure of each gas in a mixture.
What is the formula for calculating total pressure using partial pressures?
PT = P1 + P2 + P3 + PN
PT represents total pressure, while P1, P2, P3, etc., are the partial pressures of the gases.
Each gas in a mixture contributes to the total pressure, and understanding this helps in analyzing gas mixtures.
What is a real-world application of Dalton’s Law?
Scuba diving tanks
The gases in a scuba tank are regulated to maintain specific mole ratios and partial pressures.
What is the significance of mole ratio in gas mixtures?
It allows comparison of the amounts of different gases in a mixture.
The mole ratio helps in determining partial pressures and understanding gas behavior.
What are the main characteristics of an ideal gas?
- Negligible intermolecular attraction.
- Individual molecules occupy no volume.
- Elastic collisions.
- Constant random motion.
Ideal gases serve as a simplified model to describe ideal gas behavior, even though real gases do have volume and intermolecular forces.
What is the equation for calculating kinetic energy of an ideal gas?
KE = (3/2) RT
KE is the kinetic energy, R is the gas constant, and T is the temperature in Kelvin.
What is the Boltzmann distribution?
A probability distribution that describes the speeds of particles in a gas system.
It is derived from the kinetic theory of gases and relates particle speed to temperature.
What happens to the Boltzmann distribution curve as temperature increases?
The curve broadens and flattens.
The peak shifts to the right and decreases in height as temperature increases.
This is due to the increased probability of particles accumulating greater energy through collisions.
What is the relationship between temperature and average kinetic energy in the context of the Boltzmann distribution?
Higher temperature corresponds to greater average kinetic energy of particles.
This relationship is crucial for understanding particle behavior in gases.
Fill in the blank:
Diffusion occurs down a _______ _____.
concentration gradient
Diffusion is the movement of gas or liquid particles across a concentration gradient from higher to lower concentration.
Example: Smelling cookies baking from a kitchen; odor molecules move from high to low concentration.
Define:
effusion
The process by which gas molecules escape through a small opening.
Effusion occurs across a semi-permeable barrier.
Example: Helium escaping from a balloon; gas molecules cross a small opening.
What is Graham’s Law?
The rate of effusion of a gas is inversely proportional to the square root of its molar mass.
Where rate 1 and rate 2 are effusion rates, and m2 and m1 are molar masses. It relates effusion rates to molecular motion and kinetic energy.
What is the effect of kinetic energy on diffusion and effusion rates?
It increases both diffusion and effusion rates.
Higher kinetic energy correlates with faster molecular motion.
How does particle mass affect diffusion and effusion rates?
Increase in mass decreases both diffusion and effusion rates.
Heavier molecules move slower than lighter ones.
What does Boyle’s Law describe?
The relationship between pressure and volume of an ideal gas at constant temperature.
Boyle’s Law applies in an enclosed system where the number of gas molecules is constant.
It states that the product of pressure and volume must be constant.
It’s expressed as k = PV where P stands for pressure, V stands for volume, and k is a constant.
Define:
pressure
in the context of Boyle’s Law
It is the force per unit area.
The pressure a gas exerts is due to gas particles colliding with the container walls.
Mathematically, Pressure (P) = Force (N) / Area (m²)
List five units of expressing pressure.
- Pascal (Pa)
- Pounds per square inch (Psi)
- Torr
- Atmosphere (atm)
- Bar
Pascal is the SI unit of measuring pressure.
Fill in the blank:
Pressure is ______ proportional to volume according to Boyle’s Law.
inversely
If one quantity increases, the other must decrease for the product to remain constant.
When the volume is decreased, the pressure increases because gas molecules collide with the walls more frequently when volume is reduced.
What is the equation format for Boyle’s Law that simplifies calculations?
P1V1 = P2V2
This format allows for the use of initial and final values in the same equation.
What is an everyday example of Boyle’s Law?
Breathing
When lungs expand, the pressure decreases, allowing air to flow in.
Define:
Charles’ Law
The volume of a given mass of gas at constant pressure varies directly with its absolute temperature when pressure is held constant.
This law was first observed by Jacques Charles in 1787.
It is mathematically expressed as V∝T.
This indicates that volume (V) is directly proportional to absolute temperature (T).
What is the relationship between initial and final states of a gas under Charles’ Law?
V1/T1 = V2/T2
This equation helps relate the volume and temperature of a gas at constant pressure.
What temperature scale must be used in Charles’ Law?
Kelvin (K)
Temperatures in Celsius (°C) or Fahrenheit (°F) must be converted to Kelvin.
What happens to a hot air balloon as the air inside is heated?
The volume of the air expands, causing the balloon to float.
This is an application of Charles’ Law.
What is Gay-Lussac’s Law?
The direct proportionality of the temperature and pressure of a gas when volume is held constant.
It states that as temperature increases, pressure also increases, and vice versa.
What is the formula that represents Gay-Lussac’s Law?
P1/T1 = P2/T2
This formula relates the initial and final states of pressure and temperature for a gas.
For accuracy of calculations, both pressures must be in the same units, and temperatures must be in Kelvin.
List two real-life applications of Gay-Lussac’s Law.
- Aerosol bottles
- Pressure cookers
Both examples demonstrate how increased temperature leads to increased pressure, which can result in ruptures or faster cooking.
What is the ideal gas law?
It relates pressure, volume, temperature, and concentration of a pure gas.
This law can also be applied to mixtures to understand gas behavior.
What is the ideal gas law equation?
PV = nRT
P = pressure (atm), V = volume (L), n = amount of gas (mol), R = ideal gas constant, T = temperature (K) and R is a constant with the value 0.08206 L·atm/(mol·K).
What happens to gas pressure in a smaller volume?
It increases.
Restricted movement leads to more frequent collisions among gas molecules.
Fill in the blanks:
The ideal gas law fails at ____ pressures and ____ temperatures.
high; low
These conditions lead to significant intermolecular forces.
High pressure compresses gas molecules, and low temperature decreases their kinetic energy.
What are the main differences between real gases and ideal gases?
Unlike ideal gases, particles in real gases:
- Occupy volume.
- Have inelastic collisions.
- Obey Van der Waals equation .
- Have their kinetic energy varying with collisions.
Ideal gases do not occupy volume and have elastic collisions.
What is the Van der Waals equation?
(P+an²/V²)(V−nb) = nRT
This equation accounts for molecular size and intermolecular forces.
a is the degree of inter-particle attraction between gas molecules and b is the volume occupied by one mole of gas.
