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In equilibrium problems involving equilibrium constants
Chapter 14, Problem 16E(choose chapter or problem)
Problem 16E
In equilibrium problems involving equilibrium constants that are small relative to the initial concentrations of reactants, we can often assume that the quantity x (which represents how far the reaction proceeds toward products) is small. When this assumption is made, we can ignore the quantity x when it is subtracted from a large number but not when it is multiplied by a large number. In other words 2.5 - x » 2.5. but 2.5x 5* 2.5. Explain why we can ignore a small x in the first case, but not in the second.
Questions & Answers
QUESTION:
Problem 16E
In equilibrium problems involving equilibrium constants that are small relative to the initial concentrations of reactants, we can often assume that the quantity x (which represents how far the reaction proceeds toward products) is small. When this assumption is made, we can ignore the quantity x when it is subtracted from a large number but not when it is multiplied by a large number. In other words 2.5 - x » 2.5. but 2.5x 5* 2.5. Explain why we can ignore a small x in the first case, but not in the second.
ANSWER:
Solution 16EStep 1We generally represent the change in the concentration one of the reactants and products with thevariable x for equilibrium reactions. If the initial reactant concentration is very large, we canmake the assumption that .’r ‘is small relative to the initial concentration of reactant.