41644370-Midterm-1-Review - Midterm #1 Review Guide Key...

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Midterm #1 Review Guide Key Points of Chapter 17 (Equilibrium) I. A. The rate of the forward reaction is equal to the rate of the backwards reaction when a reaction is at equilibrium because the concentrations of the reactants and products no longer change and this allows the reaction to be reversible. 1. Different K values represent how much yield of products and reactants are present. a. When K is small , the reaction yields little product, therefore, there is probably no reaction overall. b. When K is large , the reaction yields little reactant, therefore, the reaction is a complete reaction. c. When there is an intermediate K, there is an equilibrium state. (i) This is when we need to use Q to direct us into which way the reaction is. If Q < K, then the reaction goes towards the products. If Q > K, then the reaction goes towards the reactants. If Q = K, then the reaction is at equilibrium state. B. The variable Q, uses the same expression in K, the only difference is, is that you can plug in molarities and solve for Q in order to determine the direction of the reaction (rules are stated in A (i)). 1. When writing the K or Q expression, we exclude pure solids and liquids II. K of Pressures versus K of Molarities A. There are two different K constants, K p and K c 1. K p is used for pressures only can be used to solve for K c by rearranging the equation. ± ²³ ´ µ¶·¸ ¹º »¼½ ¹¾ ¿ÀÁ ² µÂÃÄÅƳÃdzÈÉÃÊËÌͳÍÃÍÎĸ ϳµÂÃÄÅƳÃdzÉÅÎÌÍξͳÍÃÍÎĸ a. The R constant used for this is always the one used for the ideal gas law (0.08026) because K p is in relation to PV = NRT, therefore, we only use this constant for R. Temperature must always be in Kelvin because the ideal gas law only uses temperatures in Kelvin, if you use Celsius there will be calculation errors. III. La Chȃtelier’s Principle A. The Principle Steps to Solving An Equilibrium Problem 1. Always write the equation 2. Balance the equation 3. Read the question carefully and identify what is given/needs to be found 4. Write down the equivalences (moles to molarity, etc) and set up the I-C-E table 5. Answer the question carefully
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1. When a system at equilibrium is disturbed by adding or removing one of the substances, all of the concentrations will change until a new equilibrium point is reacted with the same value of
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41644370-Midterm-1-Review - Midterm #1 Review Guide Key...

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