✍️ Free Response Questions
AP Chemistry Free Response Questions
⚛️ Unit 1 - Atomic Structure and Properties
1.1Moles and Molar Mass
1.2Mass Spectroscopy of Elements
1.3Elemental Composition of Pure Substances
1.4Composition of Mixtures
1.5Atomic Structure and Electron Configurations
1.6Photoelectron Spectroscopy & Graph Interp.
🤓 Unit 2 - Molecular and Ionic Compound Structures and Properties
2.0Unit 2 Overview: Molecular and Ionic Bonding
2.1Types of Chemical Bonds
2.2Intramolecular Force and Potential Energy
2.3Ionic Bonding and Ionic Solids
2.4Metallic Bonding and Alloys
2.5Lewis Dot Diagrams
2.6Resonance and Formal Charge
🌀 Unit 3 - Intermolecular Forces and Properties
3.0Unit 3 Overview: Intermolecular Forces and Properties
3.2Properties of Solids
3.3Solids, Liquids, and Gases
3.4The Ideal Gas Law
3.5The Kinetic Molecular Theory of Gases
3.6Deviations from the Ideal Gas Law
3.7Mixtures and Solutions
3.8Representations of Solutions
3.9Separation of Solids/Mixtures
3.10Solubility and Solubility Rules
3.11Spectroscopy and the Electromagnetic Spectrum
3.12Quantum Mechanics and the Photoelectric Effect
🧪 Unit 4 - Chemical Reactions
4.0Unit 4 Overview: Chemical Reactions
4.1Recognizing Chemical Reactions
4.2Net Ionic Equations
4.4Physical vs. Chemical Changes
4.5Stoichiometry & Calculations
4.6Titrations - Intro and Calculations
4.8Intro to Acid-Base Neutralization Reactions
👟 Unit 5 - Kinetics
5.0Unit 5 Overview: Kinetics
5.1Defining Rate of Reaction
5.2Introduction to Rate Laws
5.3Rate and Concentration Change
5.4Writing Rate Laws
5.5Collision Model of Kinetics
5.6Reaction Energy and Graphs w/ Energy
5.7Reaction Mechanisms and Elementary Steps
5.8Writing Rate Laws Using Mechanisms
🔥 Unit 6 - Thermodynamics
6.0 Unit 6 Overview: Thermochemistry and Reaction Thermodynamics
6.1Endothermic Processes vs. Exothermic Processes
6.2Energy Diagrams of Reactions
6.3Kinetic Energy, Heat Transfer, and Thermal Equilibrium
6.4Heat Capacity and Coffee-Cup Calorimetry
6.5Phase Changes and Energy
6.6Introduction to Enthalpy of Reaction
6.7Bond Enthalpy and Bond Dissociation Energy
6.8Enthalpies of Formation
⚖️ Unit 7 - Equilibrium
🍊 Unit 8 - Acids and Bases
8.0Unit 8 Overview: Acids and Bases
8.1Introduction to Acids and Bases
Unit 9 - Applications of Thermodynamics
🤺 AP Chemistry Essentials
🧐 Multiple Choice Questions
AP Chemistry Self-Study and Homeschool
⏱️ 4 min read
August 6, 2020
Interactions between solvents and solutes can be represented with particle/molecule diagrams.
Solutions in which water is the dissolving medium are called aqueous solutions💧. Any substance whose aqueous solution contains ions is called an electrolyte. Any substance that forms a solution containing no ions is a nonelectrolyte.
Electrolytes that are present in solution entirely as ions are strong electrolytes, whereas those that are present partly as ions and partly as molecules are weak electrolytes.
Electrolytes are substances that would generate electricity in a solution. This is explained by the presence of ions in the solution.
Strong electrolytes include soluble salts, strong acids, and strong bases. These completely dissociate in a solution of water. To dissociate is to split up into its cations and anions. An example of a strong electrolyte would be HCl and when dissolved, the H+ ions are split apart from the Cl- ions.
To recall (this should be memorized):
|Strong Acids||Strong Bases|
|HNO3||any group 1 metal + OH-|
Weak electrolytes include weak acids and weak bases. These partly dissociate in a solution of water, so only some molecules would split up into their ions (which explains why they are present as both ions and molecules).
Nonelectrolytes are molecular compounds which don't conduct electricity. An example would be sugar🍬.
The solubility of ionic substances is made possible by solvation. Acids and bases are critical electrolytes as mentioned above. Acids are proton donors; they increase the concentration of H+ (aq); bases are proton acceptors-they increase the concentration of OH- (aq). Knowing the basic properties of these electrolytes can help you recognize compounds that are in certain solutions.
When knowing how different solutions act regarding electrolytes, acids, and bases, you can visualize how particles interact in a solution:
Electrolytes dissolve into ions, Image Courtesy of Kesley Putman
In the above images, you can see two dissolved substances, one being a strong electrolyte and the other being a non-electrolyte. Since the NaCl solution shows dissolved ions, we know that it will conduct electricity.
When discussing solutions, colligative properties are properties that depend upon the concentration of solute molecules or ions, but not upon the identity of the solute. For example, a solution of 6M NaCl will act a lot differently than simply pure water.
There are 3 main colligative properties (You may learn 4, including osmotic pressure, but it will not be directly tested on the AP Exam):
When a solute is dissolved in a solvent, you decrease the tendency for water molecules💧 to evaporate into the gas phase♨️. This means that there will be less gas above the surface of the liquid, leading to a lower vapor pressure.
There is a formula for finding the exact new vapor pressure.
Raoult's Law - P1 = XP0, where P1 is the new vapor pressure, X is the mole fraction of the solute, and P0 is the initial vapor pressure.
The red solute particles block gas from escaping, leading to a lower vapor pressure. Image Courtesy of MisterChemistry
Applying a non-volatile solution decreases the solution's vapor pressure by Raoult's Law (another name for lowering vapor pressure). Then, the temperature must be increased🌡️ to return the vapor pressure to the pure solvent value. This means that as you add more and more solute, the temperature at which the solution boils increases⬆️.
A good example of this is when you make pasta🍝. Chefs around the world always recommend that you salt your water before you add pasta🧂, and while this of course is to add flavor, it also actually raises the boiling point of your water, making your pasta cook quicker!
This same principle is seen in chemistry with solutions. There is another formula to calculate the exact elevation.
ΔTb = km, where ΔTb is the change in boiling point, k is a specific constant, and m is the molality of the solute (molality is a measure of concentration that is mol solute/kg solvent).
The same applies for freezing-points of solutions. As boiling point elevates, freezing point depresses, or lowers.
This means that, for example, a solvent may have a freezing point of 0 degrees Celsius without any solute, and then once you dissolve some solute, the freezing point will lower to -1.5 degrees Celsius.
A good example of this is if you live in the North, you are well accustomed to adding salt to ice in order to melt it❄️. The key reason for this is not a reaction occuring, but actually the freezing-point of the ice decreasing, turning it into a liquid.
💡Fun fact, ice melting salt is actually not NaCl! It's typically CaCl2 since it will split into more solute particles, thus decreasing the freezing-point even more! NaCl splits up into two ions whereas CaCl2 splits p into 3 ions.
The formula for freezing-point depression is very similar to boiling-point elevation; it is ΔTf = -km. 🎥Watch: AP Chemistry - Representations of Solutions
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