Solving Problems When Not All Equilibrium Concentrations Are Known

SOLVING PROBLEMS WHEN NOT ALL EQUILIBRIUM CONCENTRATIONS ARE KNOWN 

Occasionally, not all equilibrium concentrations are known. When this occurs you must use equilibrium concepts and stoichiometry concepts to determine K. What you are trying to do in these problems is determine the amounts of materials at equilibrium. In Chapter 12, you learned that the balanced chemical equation shows you the relative amounts of reactants and products during the chemical reaction. For a reaction at equilibrium, the logic is the same. The mole ratios still apply. There is one major difference, however, between the stoichiometry 

Step 2. Create a table with three rows and as many columns as there are constituents (reactants and products). The three rows should be labeled Start (for initial concentration or pressure), A (change in concentration or pressure), and Finish (equilibrium concentration or pressure). 

Step 4. For any substances where the initial and equilibrium concentrations are known, determine the change in concentration (A). 

Step 5. Use the stoichiometric relationships (mole ratios) in the reaction to fill in the remaining blanks (review Chapter 12 if you have forgotten this). 

Step 6. Once the table is completed, use the values to determine the equilibrium constant. 

When 2.00 mole each of hydrogen (H ) and iodine (I,) are mixed in an evacuated 1.00 L vessel, 3.50 mole of HI are produced. What is the value of the equilibrium constant, 

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Solving problems when not all equilibrium concentrations are known... 

The Reaction Quotient Solving Problems When Not All Equilibrium Concentrations Are Known... 

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