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Questions and Answers
What is the standard pressure defined at STP?
What is the standard pressure defined at STP?
The molar volume of a gas at STP is 22.41 L.
The molar volume of a gas at STP is 22.41 L.
True
What is the temperature at Standard Temperature and Pressure (STP) in Kelvin?
What is the temperature at Standard Temperature and Pressure (STP) in Kelvin?
273.15 K
At STP, one mole of an ideal gas occupies _______ L.
At STP, one mole of an ideal gas occupies _______ L.
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Match the following gas laws with their correct descriptions:
Match the following gas laws with their correct descriptions:
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According to Boyle's Law, what happens to the pressure when the volume of a gas is halved?
According to Boyle's Law, what happens to the pressure when the volume of a gas is halved?
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Charles's Law pertains to the relationship between temperature and volume of a gas.
Charles's Law pertains to the relationship between temperature and volume of a gas.
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Who was the first to change one variable to determine how another variable changes, leading to the formulation of Boyle's Law?
Who was the first to change one variable to determine how another variable changes, leading to the formulation of Boyle's Law?
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When we breathe, our body is exploiting __________ Law.
When we breathe, our body is exploiting __________ Law.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What does the average kinetic energy of gas molecules depend on?
What does the average kinetic energy of gas molecules depend on?
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Which parameter is NOT an intensive property?
Which parameter is NOT an intensive property?
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The volume of gaseous species is significant when considering molecular behavior.
The volume of gaseous species is significant when considering molecular behavior.
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What happens to the average kinetic energy of gas molecules if the temperature is doubled?
What happens to the average kinetic energy of gas molecules if the temperature is doubled?
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The atmospheric pressure is caused solely by the movement of gas molecules.
The atmospheric pressure is caused solely by the movement of gas molecules.
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What is the SI unit of pressure?
What is the SI unit of pressure?
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Gas species collide with each other but do not _____ with one another.
Gas species collide with each other but do not _____ with one another.
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The volume of a gas is considered a(n) ______ property.
The volume of a gas is considered a(n) ______ property.
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Match the following properties of gases with their descriptions:
Match the following properties of gases with their descriptions:
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Match each pressure unit with its equivalent value:
Match each pressure unit with its equivalent value:
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How do gas molecules exert pressure in a container?
How do gas molecules exert pressure in a container?
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Pressure is affected by the size of the gas sample.
Pressure is affected by the size of the gas sample.
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Which force is responsible for atmospheric pressure?
Which force is responsible for atmospheric pressure?
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What is the primary function of a barometer?
What is the primary function of a barometer?
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A manometer can only be used to measure absolute pressure.
A manometer can only be used to measure absolute pressure.
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Who invented the barometer?
Who invented the barometer?
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At sea level, standard atmospheric pressure equals __________ mm Hg.
At sea level, standard atmospheric pressure equals __________ mm Hg.
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Which equation correctly describes hydrostatic pressure at a height?
Which equation correctly describes hydrostatic pressure at a height?
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Boyle's Law describes the inverse relationship between pressure and volume.
Boyle's Law describes the inverse relationship between pressure and volume.
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Match the following pressure types with their definitions:
Match the following pressure types with their definitions:
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Blood pressure readings are commonly expressed as __________ over __________.
Blood pressure readings are commonly expressed as __________ over __________.
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What determines the distribution of molecular velocities?
What determines the distribution of molecular velocities?
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Molecules move at the same velocity regardless of their mass.
Molecules move at the same velocity regardless of their mass.
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What is the average distance between collisions called?
What is the average distance between collisions called?
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At sea level, the mean free path for air is approximately ____ nm.
At sea level, the mean free path for air is approximately ____ nm.
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How do gases at atmospheric pressure diffuse compared to other states of matter?
How do gases at atmospheric pressure diffuse compared to other states of matter?
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The average kinetic energy of molecules is directly related to their velocity.
The average kinetic energy of molecules is directly related to their velocity.
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What is the term used to describe the spread of substances through space?
What is the term used to describe the spread of substances through space?
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Study Notes
Lecture 2 Announcements
- Today's Topics: Brown 10.1 Characteristics of Gases, 10.2 Pressure, 10.3 The Gas Laws, 10.4 The Ideal Gas Equation, 10.5 Gas Mixtures and Partial Pressures, 10.6 The Kinetic-Molecular Theory of Gases, 10.7 Molecular Effusion and Diffusion, 10.8 Real Gases: Deviations from Ideal Behavior
- Problem Set 1: Due tomorrow, upload as a PDF on Moodle
- Tutorials: Completed after Exercise 2
- Useful Info Sheets: Found on Moodle, exam-related information sheets
Lecture 3
- Next Week's Topics: Brown 4.1 General Properties of Aqueous Solutions, 4.2 Precipitation Reactions, 4.3 Acids, Bases, and Neutralization Reactions, 4.4 Oxidation-Reduction Reactions, 4.5 Concentrations of Solutions
Review
- Lecture 1 topics: Definitions, nomenclature, elements, compounds, mixtures, atoms, atomic structure, atomic number, mass number, isotopes, periodic table, molecules, formulas, structural formulas, representations, ions, and ionic compounds
- Lecture 1 transition to Lecture 2: Discussion of chemical reactions, change one substance into another, chemical equations, stoichiometry, balancing equations, formula weights, mole, Avogadro's number, molar mass
- Atomic structure: Nucleus (protons and neutrons), electron cloud ( ~1Å to ~5Å)
Example Chemical Reaction
- Chemical equation: 2 H₂(g) + O₂(g) → 2 H₂O(l)
- Molecular interpretation: 2 molecules H₂, 1 molecule O₂, 2 molecules H₂O
- Mole-level interpretation: 2 mol H₂, 1 mol O₂, 2 mol H₂O
- Molar masses: 4.0 g H₂, 32.0 g O₂, 36.0 g H₂O
Types of Chemical Reactions
- Combustion: Reacting with O₂, example CH₄ + 2O₂ → CO₂ + 2H₂O (combustion of methane)
- Combination: A + B → C, example C(s) + O₂(g) →CO₂(g), N₂(g) + 3H₂(g) → 2NH₃(g) (burning coal, fixation of nitrogen)
- Decomposition: C → A + B, example 2 H₂O(l) → 2H₂(g) + O₂(g), CaCO₃(s) → CaO(s) + CO₂(g) (electrolysis of water, cement/concrete)
Today's Topic: Gases
- Three states: Solid, liquid, vapor
- Example: H₂O
- Gas properties: Similar physical properties, even with different chemical properties, expand to fill the container, compressible, and form homogeneous mixtures. Molecules occupy a small portion of the total volume.
Common Gases at Room Temperature
- Provides a table of common gases at room temperature with formulas, names, and characteristics (toxic, odor, color).
Parameters to Describe Gases
- Parameters: Volume (V), Amount (n, moles), Temperature (T), Pressure (P)
- Type: Extensive properties (depend on sample size) and intensive properties (do not depend on sample size or volume)
Origin of Pressure
- Pressure is caused by molecules moving and hitting surfaces.
- Atmospheric pressure is due to Earth's gravity acting on a column of air.
- Standard atmospheric pressure is approximately 100 kPa or 1 bar.
Measuring Atmospheric Pressure
- Barometer: measures atmospheric pressure using mercury.
- 760 mm Hg = 1 atmosphere (atm) = 101.325 kPa = 1.01325 bar
Measuring Relative Pressure
- Manometer: measures the pressure difference between a gas and the atmosphere.
P-V Relationship (Boyle's Law)
- Keep n and T constant: Pressure and volume are inversely proportional
- PV = constant, or P = constant * 1/V
V-T Relationship (Charles's Law)
- Keep n and P constant: Volume and temperature are directly proportional
- V = constant * T, or V/T = constant
V-n Relationship (Avogadro's Law)
- Keep P and T constant: Volume and number of moles is directly proportional
- V = constant * n, or V/n = constant
Standard Temperature and Pressure (STP)
- Defined as T=0°C (273.15K), and P=1 atm (101.325 kPa)
- Molar volume at STP is 22.41 L
Ideal Gas Law (IGL)
- PV = nRT
- where R is the gas constant with different values in different units.
Assumptions in IGL
- Molecules in gases do not interact, negligible volume compared to the total volume, and the amount of gas depends on the number of gaseous species present
Using Ideal Gas Law
- Type 1: Find a missing variable if three of the four (P, V, n, T) are known. Rearrange the IGL to isolate the unknown variable.
- Type 2: Two variables remain constant (n, T, etc.) while two other variables change. Rearrange IGL for desired relations like PV/T
Type 3
- One variable is constant and three other variables are changing. Using the IGL by isolating the variable and plugging in values to find the unknown
Other Uses of IGL
- Density: Rearranging IGL, the density of a gas can be determined if molar mass (Mw), pressure (p), and temperature (T) are known
Partial Pressures/Gaseous Mixtures
- Total pressure (Ptot): Depends on total number of moles, where the Ptot = P₁ + P₂ + ... + Pi.
- Partial Pressure: Individual pressure contributions from each component
Mixtures and Mole Fraction
- Mole fraction means, X₁ = nᵢ / nₜₒₜ where i is a component, meaning in a mixture
Kinetic-Molecular Theory of Gases
- Molecules are randomly moving with constant kinetic energy.
- Gas molecules occupy negligible volume
- Gas molecules collide but do not interact.
- Average Ek depends on temperature (T)
Velocity Distributions
- Molecules move with a range of velocities, depending on temperature and molecular mass.
- Distribution shifts to higher velocities with higher temperatures, and lower velocities for heavier molecules.
- The area under the speed distribution should always add up to 1.0
Special Velocities
- Vmp: Most probable speed
- Vav: Average speed
- Vrms: Root mean square speed (speed of a molecule with kinetic energy equal to the average kinetic energy of all molecules)
Diffusion
- Gases diffuse at much slower speeds than their RMS speed.
- Mean free path is dependent on different factors, such as pressure.
Nonidealities in Gases
- High Pressure: Volume occupied by molecules is no longer negligible
- Low Temperature: Molecules interact strongly with each other.
- Van der Waals Equation: Modifies IGL to account for molecular interactions and volume.
Next time: Reactions in Water
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Description
This quiz covers fundamental concepts related to Standard Temperature and Pressure (STP) and gas laws such as Boyle's and Charles's laws. Test your knowledge on the relationships between temperature, volume, and pressure of gases, as well as the properties of gases at STP. Ideal for students studying chemistry or physics.
