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<center><b>Equilibrium: Calculating Equilibrium Constant,K: (Knowing Equilibrium Info)</b></center> <br> <b>Procedures for Calculating any Equilibrium Constant Problem </b> <br> Step 1 : Write down balanced chemical reaction<br> Step 2 : Determine and write down the Equilibrium Constant Expression (K=<nowiki>[products]</nowiki><sub>E</sub>/<nowiki>[reactant]</nowiki><sub>E</sub>) where E = Equilibrium conditions.<br> Step 3: Plug in and do math to solve for unknown. (3 Levels of Difficulty)<br> <I>Level 1 : Simplest Difficulty</i><br> *Problems gives all equilibrium concentration and you are solving for K (would be nice to figure out units also). See example below. *Problem gives all equilibrium concentrations except one and gives value of K (you need to determine units of K) and solving for last equilibrium concentration., ([http://www.tmcleod.org/Level1/Chem328KineticEquil/Chem328ExampleofWorkSimpleEquilibrium.pdf Example of Work for Simple Equilibrium Problems]. Remember, you need to manipulate the equation, in this case, equilibrium constant expression into a form with your unknown on one side of equal sign and all other variable on other side of equal sign. <br> <i>Level 2 : ICE Box without "x" (have one piece of information at equilibrium)</i><br> *[[Direction on Calculation ICE Box without "x" Problems] * For example of work, click here [http://www.tmcleod.org/Level1/Chem328KineticEquil/Chem328ExampleofWorkICEBox.pdf Example of Work for a Simple ICE Box (no x)] <br> <i>Level 3 : ICE Box with "x" (will not do in 1st year, but will in AP Chem)</i><br> ##Sometimes they give all equilibrium concentrations and look for Equilibrium constant (K). ##Sometime they give K and you are looking for one of the species' equilibrium concentration (they give all other species' equilibrium concentrations) ##Sometimes they give concentration of one reactant and/or product at equilibrium and all other species' initial concentrations and you are calculating K. **<b>If this occurs, all you Wizards of Stoichiometry need to set-up <nowiki>ICE Box table</nowiki>.</b> **i. Change mole and container of initial conditions into concentration (Molarity, M). **ii. Convert one piece of equilibrium to mole or M reacted. **iii. Take M reacted and use stoichiometry to determine amount of all other species reacted or producted in rxn **iv. Use math on table to determine equilibrium concentration of all species. <br> <b>Example 1</b><br> Calculate the Equilibrium constant for the following reversible reaction @25<sup>o</sup>:<br> 2 NO<sub>(g)</sub> + 1 O<sub>2 (g)</sub> <==> 2 NO<sub>2 (g)</sub><br> where the equilibrium concentration of NO,O<sub>2</sub>,and NO<sub>2</sub> are 2.00M,4.00M,and 3.00M, respectively.<br> <b>Answer:</b><br> Step 1: Balanced chemical reaction. See question<br> Step 2: Write down Equilibrium constant expression: <br> K= {NO<sub>2 (g)</sub>}<sup>2</sup> / {O<sub>2 (g)</sub>}<sup>1</sup>{NO<sub>(g)</sub>}<sup>2</sup><br> But write it like this :<br> <br> Step 3: plug in known information into Equilibrium constant expression directly since you know all equilibrium concentration.<br> K = (3.00M)<sup>2</sup> / {(2.00M)<sup>2</sup>)(4.00M)<sup>1</sup>}<br> K=0.5625 = 0.563 (for K, we don't usually have units)<br> <br> <br>
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