CHEMDUNN

This episode introduces chemical equilibrium, defining it as the point where the rate of the forward reaction equals the rate of the reverse reaction. This process is dynamic, meaning the reaction hasn't stopped, but the concentrations of all substances have become constant, though not necessarily equal. Equilibrium is indicated by a double arrow. The system's preference for either reactan...

This episode explains rate comparisons in chemical kinetics, focusing on how the rate of change for each substance in a chemical reaction is related through the stoichiometry of the balanced equation. It introduce a general rate expression where the rate of change in concentration for each reactant and product is divided by its respective coefficient to determine the overall reaction rate. Using t...

This episode demystifies the Integrated Rate Laws, the essential chemical kinetics equations that allow chemists to predict the exact concentration of a reactant​ at any given time. While standard rate laws show instantaneous speed, the integrated versions, derived using calculus, link concentration and time directly. The episodes explore the three main laws for zero-order, first-order, and second...

This episode explains how to calculate the enthalpy of a reaction (ΔHrxn​) using average bond enthalpies. This method is based on the principle that breaking old bonds requires energy and forming new bonds releases energy. The core formula is ΔHrxn​=Σ(bonds broken)−Σ(bonds formed), where "bonds broken" refers to the energy of the reactant bonds and "bonds formed" is the energy...

This episode explains how to calculate the enthalpy change of a reaction using standard enthalpies of formation, which are values representing the energy required to form one mole of a compound from its elements. The episode introduces the "products minus reactants" formula. It emphasizes a key fact: the enthalpy change of formation​ for any pure element in its most stable form is zero....

This episode explains calorimetry, the science of measuring heat transfer, based on the Law of Conservation of Energy. It demonstrates how to use the formula q=m⋅c⋅ΔT to solve for unknown variables in two common scenarios. First, the specific heat of an unknown metal is determined by measuring the heat it loses to water in a calorimeter. Second, the enthalpy change of a neutralization reaction is...

This episode explains Hess's Law, a method for calculating the enthalpy change of a reaction by treating it as a sum of other known reactions. It presents three key rules for manipulating these equations: reversing an equation changes the sign of its ΔH, multiplying an equation by a coefficient requires multiplying its ΔH by the same number, and adding equations together means adding their ΔH...

This episode provides a clear, concise summary of specific heat capacity and its use in thermochemistry. It introduces the fundamental concept that specific heat capacity, represented by the symbol c, is a measure of how much thermal energy a substance can store. The episode focuses on the key equation q=m⋅c⋅ΔT as the central formula for calculating heat transfer. 

A heating or cooling curve graphically represents the relationship between heat, temperature, and the physical state of a substance. The curve has sloped sections where the temperature changes as heat is added, and the substance remains in a single phase (solid, liquid, or gas). The formula q=mcΔT is used to calculate the heat involved in these sections. The curve also has flat plateaus where the...

Enthalpy (ΔH) is the heat change in a chemical reaction and can be shown in two ways: either written with the equation or included as a reactant or product. A negative ΔH signifies an exothermic reaction that releases heat, which can be shown as a product in the equation. A positive ΔH signifies an endothermic reaction that absorbs heat, which can be shown as a reactant. In stoichiometry problems,...

Energy diagrams are a visual tool to understand the energy changes in chemical reactions. They map the reaction from reactants to products, with the vertical axis showing potential energy. The difference in energy between the start and end points is the enthalpy change (ΔH). A peak in the diagram represents the transition state, and the energy needed to reach it from the reactants is the activatio...

Heat transfers in three primary ways: conduction, convection, and radiation. Conduction is direct heat transfer through physical contact, common in solids like a metal spoon in hot soup. Convection is heat transfer through the movement of fluids (liquids or gases), where warmer, less dense fluid rises and cooler, denser fluid sinks, creating a continuous flow, as seen when boiling water. Radiation...

Colligative properties are solution properties that depend on the number of solute particles, not their identity. The episode focuses on freezing point depression and boiling point elevation. In these calculations, m is molality (moles of solute per kilogram of solvent), Kf​ and Kb​ are solvent-specific constants found on a reference table, and i is the van 't Hoff factor, which accounts for h...

Ionic equations provide a more accurate view of reactions in solution than a simple chemical equation. A complete ionic equation shows all dissolved ionic compounds as separate ions, while solids, liquids, and gases remain intact. From this, a net ionic equation is derived by removing spectator ions—those that remain unchanged on both sides of the reaction. The final net ionic equation shows only...

Dilution is the process of lowering a solution's concentration by adding more solvent while keeping the amount of solute constant. This process is governed by the equation M1​V1​=M2​V2​, where M is molarity and V is volume, with subscripts 1 and 2 referring to the initial stock solution and the final diluted solution, respectively. This formula is used to calculate the volume of a concentrated...

Real gases deviate from ideal behavior under high pressure and low temperature because the assumptions of the ideal gas law break down. At high pressure, the volume of gas molecules themselves becomes significant, making the gas less compressible than predicted. At low temperature, weak attractive forces between molecules become noticeable, causing the gas to be more compressible and exert lower p...

The Maxwell-Boltzmann distribution shows that molecules in a gas don't all move at the same speed, but rather follow a predictable statistical pattern. The curve representing this distribution shows a peak for the most probable speed and a long tail indicating that some molecules move very fast. The distribution is significantly affected by temperature, which shifts the entire curve toward hig...

Graham's Law states that a gas's rate of diffusion or effusion is inversely proportional to the square root of its molar mass. In simple terms, lighter gases move faster than heavier ones. This relationship comes from the fact that all gases at the same temperature have the same average kinetic energy, meaning a lighter molecule must move faster to have the same energy as a heavier one. Th...

This episode explains Dalton's Law of Partial Pressures, which states that the total pressure of a gas mixture is the sum of each gas's individual pressure. This works because, at the molecular level, each gas acts independently. The episode gives examples, including collecting a gas over water, where the total pressure must be corrected for water vapor pressure. It also introduces the con...

This episode on kinetic molecular theory (KMT) explains gas behavior through five fundamental postulates. These are: gas molecules are in constant, random motion; they have negligible volume; there are no intermolecular forces between them; all collisions are perfectly elastic; and their average kinetic energy is directly proportional to absolute temperature. This framework helps explain gas laws...

This episode explains the Ideal Gas Law as a universal equation that combines all the individual gas laws. It introduces the equation's components—pressure (P), volume (V), moles (n), the universal gas constant (R), and absolute temperature (T) in Kelvin—and emphasize the importance of using the correct units for R. The episode outlines a systematic approach for solving problems and provides e...

This episode explains three additional gas laws including the unifying Combined Gas Law. It first introduces Gay-Lussac's Law, which states that pressure is directly proportional to absolute temperature at constant volume. Next, it covers Avogadro's Law, which describes the direct relationship between a gas's volume and the number of moles. The episode then introduces the Combined Gas...

This episode explains two fundamental gas laws: Boyle's Law and Charles's Law. It explains that Boyle's Law describes the inverse relationship between pressure and volume at constant temperature, using a scuba diving example to illustrate how an increase in pressure causes a decrease in volume. Charles's Law describes the direct relationship between a gas's volume and its absol...

This episode explains how to perform solution stoichiometry using molarity as the key conversion factor. It breaks down the process into a simple flow: use molarity to convert solution volume to moles, apply the mole ratio from the balanced equation, and then convert to the final requested units. It provides examples, including a limiting reactant problem, and highlight common mistakes such as for...

This episode explains how to perform non-STP gas stoichiometry using the Ideal Gas Law (PV=nRT). It emphasizes that this method is crucial for real-world applications where gases are not at standard conditions, rendering the 22.4 L/mol conversion factor invalid. The episode demonstrates how to use the Ideal Gas Law to convert gas volumes to moles and vice versa, even in problems involving mixed co...