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New videos from Khan Academy 2021-07-21T16:07:24.161336
Updated: 16 hours 43 min ago

Visual line

Wed, 2021-07-21 16:07
How line is used in visual storytelling.

William Morris: Useful Beauty in the Home

Fri, 2021-07-09 19:47
William Morris: Useful Beauty in the Home from HENI Talks on YouTube. Discover the radical politics of interior design in the Arts & Crafts movement. Additional creative commons information: Philip Speakman Webb Charles Fairfax Murray, 1873 NPG 4310 © National Portrait Gallery, London (CC BY-NC-ND 3.0) https://creativecommons.org/licenses/by-nc-nd/3.0/

Ben Shahn, Contemporary American Sculpture

Fri, 2021-07-09 05:38
Ben Shahn, Contemporary American Sculpture, 1940, tempera on board, 21 1/2 x 30 inches (The John and Susan Horseman Collection, Courtesy of the Horseman Foundation) A conversation with Dr. Jeffrey Richmond-Moll (Curator of American Art, Georgia Museum of Art) and Dr. Beth Harris

3 tips for using Khan Academy videos

Thu, 2021-07-08 20:17
Want to learn how teachers are using Khan Academy videos with their students? This is your chance to get advice directly from teachers!

Worked example: Calculating equilibrium concentrations from initial concentrations and the equilibrium constant

Thu, 2021-07-08 05:13
In this video, we'll learn how to use initial concentrations and the equilibrium constant to calculate the concentrations of reaction species at equilibrium.

Worked example: Predicting whether a precipitate forms by comparing Q and Kₛₚ

Thu, 2021-07-08 05:13
We can use the reaction quotient to predict whether a precipitate will form when two solutions containing dissolved ionic compounds are mixed. If Q < Kₛₚ, the newly mixed solution is undersaturated and no precipitate will form. If Q > Kₛₚ, the solution is oversaturated and a precipitate will form until Q = Kₛₚ.

Le Chȃtelier’s principle: Changing volume

Thu, 2021-07-08 05:13
Le Chȃtelier’s principle can be used to predict the effect that a stress like changing volume has on a system at equilibrium. If the volume of the container is increased (at constant T), the system will shift in the direction that increases the number of moles of gas in the container. If the volume is decreased, the reverse effect will occur. If the system has the same number of moles of gas on both sides of the chemical equation, a change in volume will have no impact on the equilibrium position.

Worked examples: Calculating equilibrium constants from equilibrium concentrations or partial pressures

Thu, 2021-07-08 05:13
In this video, we'll calculate equilibrium constants using measurements of concentration and partial pressures at equilibrium. First, we'll find Kc for an equilibrium system using equilibrium concentrations. Then, we'll find Kp for a different system using equilibrium partial pressures.

Worked example: Calculating the equilibrium total pressure after a change in volume

Thu, 2021-07-08 05:13
How does the total pressure change when the volume of a gaseous equilibrium system is reduced? In this video, we'll explore the answer to this question using both qualitative and quantitative approaches.

Le Chȃtelier’s principle: Changing temperature

Thu, 2021-07-08 05:13
Le Chȃtelier’s principle can be used to predict the effect that a stress like changing temperature has on a system at equilibrium. If the temperature of the system is increased (at constant V), the system will shift in the direction that consumes the excess heat. If the temperature of the system is decreased, the reverse effect will be observed.

Properties of the equilibrium constant

Thu, 2021-07-08 05:13
The equilibrium constant for a reaction depends on how the balanced equation is written. If the equation is reversed, K is inverted. If the equation is multiplied by a factor n, K is raised to the nth power. If multiple equations are added together, K for the overall equation is the product of the K values for the equations that were summed.

Writing equilibrium constant and reaction quotient expressions

Thu, 2021-07-08 05:13
The equilibrium constant, K, describes the relative amounts of reaction species at equilibrium. The expression for K is equal to the concentrations (or partial pressures) of the products raised to their stoichiometric coefficients divided by the concentrations (or partial pressures) of the reactants raised to their stoichiometric coefficients. The reaction quotient, Q, has the same form as K but describes the relative amounts of reaction species at any point in time.

Worked example: Using the reaction quotient to find equilibrium partial pressures

Thu, 2021-07-08 05:13
In some equilibrium problems, we first need to use the reaction quotient to predict the direction a reaction will proceed to reach equilibrium. Once we know this, we can build an ICE table, which we can then use to calculate the concentrations or partial pressures of the reaction species at equilibrium.

Magnitude of the equilibrium constant

Thu, 2021-07-08 05:13
The magnitude of the equilibrium constant provides information about the relative amounts of reactants and products at equilibrium. A large K value (greater than 1) indicates that there are more products than reactants at equilibrium, while a small K value (less than 1) indicates that there are more reactants than products at equilibrium.

Dynamic equilibrium

Thu, 2021-07-08 05:13
Many physical and chemical processes are reversible. A reversible process is said to be in dynamic equilibrium when the forward and reverse processes occur at the same rate, resulting in no observable change in the system. Once dynamic equilibrium is established, the concentrations or partial pressures of all species involved in the process remain constant.

Le Chȃtelier’s principle: Changing concentration

Thu, 2021-07-08 05:13
Le Chȃtelier’s principle can be used to predict the effect that a stress like changing concentration has on a reaction system at equilibrium. If the concentration of a reaction species is increased (at constant T and V), the equilibrium system will shift in the direction that reduces the concentration of that species. If the concentration of a reaction species is decreased, the reverse effect will be observed.

Worked example: Using Le Chȃtelier’s principle to predict shifts in equilibrium

Thu, 2021-07-08 05:13
In this video, we'll use Le Chȃtelier’s principle to predict how an equilibrium system will shift in response to various stresses, including changes in concentration, volume, and temperature.

Worked example: Calculating an equilibrium constant from initial and equilibrium pressures

Thu, 2021-07-08 05:13
Given an initial partial pressure and the total pressure at equilibrium, we can use Dalton's law to determine the equilibrium partial pressures of the gases in a reaction mixture. Once we know the equilibrium partial pressures, we can calculate the equilibrium constant for the reaction.

Direction of reversible reactions

Thu, 2021-07-08 05:13
For a reversible reaction, if the rate of the forward reaction is greater than the rate of the reverse reaction, there is a net conversion of reactants to products. If the rate of the forward reaction is less than the rate of the reverse reaction, there is a net conversion of products to reactants. If the two rates are equal, the reaction is at equilibrium.

Using the reaction quotient

Thu, 2021-07-08 05:13
By comparing the reaction quotient to the equilibrium constant, we can predict the direction a reaction will proceed to reach equilibrium. If Q < K, the reaction will proceed towards the products. If Q > K, the reaction will proceed towards the reactants. If Q = K, the reaction is already at equilibrium and will not change.

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