Our learning objectives for our next class are to:
- be able to predict how a change in a system will affect the equilibrium concentrations, based on K;
- Use K to predict equilibrium concentrations when only given initial concentrations.
Before class on Feb. 3:
- Please watch the 2 videos below (7 min, 25 min)
- Complete the notes
- Make a comment.
chemistry matters 
I learned how to calculate the amounts of reactants and products present at equilibrium when the equilibrium constant is known. I also learned what the reaction quotient is and how the direction of a reaction will change depending on what Q is.
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In these videos, I learned how to use equilibrium constants to discover more information about which direction the reaction will react in, as well as the reactants and products. If q is less than k, then more product will be made and the reaction will be forward/to the right. If q is greater than k, then the reaction will react to the left/reverse to make more products. Q can be found by using initial concentrations instead of equilibrium concentrations in the equilibrium equation. Since reactions give us the proportion of the concentrations/pressures in the reactants/products in the coefficients, we can plug x in for changes in concentration. Then we can subtract/add these X’s to the initial concentrations and plug these new expressions into the equilibrium equation and set itequal to the given equalibrium constant. Since there is only one variable, we can then use elements of algebra such as the quadratic equation to solve for the value of x.
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I was wondering and thought something seemed off. In the video, at 14:24, shouldn’t it be -46.5x^2 -151.x + 101? I’m pretty sure the -46.5x^2 remains negative even when you kick it to the front since it is negative the whole time.
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These videos showed me how to use the Reaction Quotient, or Q, in order to find out which the reaction shifts. I also learned of another way of calculating the concentrations, or pressure, of the substances using the Quadratic Formula.
Question: Would the direction of the reaction not change when volume changes because both the reactants and the products would be changing with the same proportions?
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In this tutorial, I learned how to solve for the equilibrium constant when only the initial concentration is known. First, you subtract what is on the reactants side and add what is on the products side. We should use a variable for our unknown change in concentration. Once it is manipulated into a quadratic equation, we then plug it into the quadratic formula. Since two answers are usually found, only one will be correct. The negative one is usually always wrong.
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