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Lessons 5-10 Equilibrium. CDT Clothier CDT Selleck. Agenda. Objectives Equilibrium constant/equilibrium concentration RICE tables Le Chatelier’s Principle Solubility Problem Question and Answer. Objectives. Understand the relationship between K and Q and how to use them
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Lessons 5-10Equilibrium CDT Clothier CDT Selleck
Agenda • Objectives • Equilibrium constant/equilibrium concentration • RICE tables • Le Chatelier’s Principle • Solubility • Problem • Question and Answer
Objectives • Understand the relationship between K and Q and how to use them • Use RICE tables to calculate the equilibrium concentration of reactants or products • Predict the effect on equilibrium for certain disturbances using Le Chatelier’s Principle • Predict if a precipitate will form in a reaction
Equilibrium • Q<K, product favored Q>K, reactant favored Q=K, equilibrium
RICE Table H2(g) + I2(g) Used to solve for equilibrium concentrations If given K, make reaction quotient expression and solve for x Remember that you can assume x away and check to see if the assumption is justified (<5% error)
Le Chatelier’s Principle • When a chemical system at equilibrium is disturbed, it re-attains equilibrium by undergoing a net reaction that reduces the effect of the disturbance. • Concentration: no effect on K but if there is an increase/decrease in reactant the net direction of reaction is toward the product and vice-versa. • Pressure: no effect on K but an increase in P decreases V which causes formation of fewer moles of gas and vice-versa. • Temperature: K changes by van’t Hoff equation and an increase in T moves the reaction toward absorption of heat and vice-versa.
Solubility • Determine solubility with a RICE table • Common Ion effect: the presence of a common ion decreases the solubility of a slightly soluble ionic compound. • Qsp=Ksp, solution is saturated, no change Qsp>Ksp, precipitate forms until saturated Qsp<Ksp, solution unsaturated, no precipitate
Problem • Calculate the new equilibrium concentrations of [Ag] and [CN] when 5.00 moles of silver cyanide, AgCN decomposes in a 3 L container if the temperature is raised from 300 degrees Celsius to 500 degrees Celsius. Kc at 300 degrees Celsius is .068 and the standard heat of reaction is -126.05 kj/mol. • Note: all values are made up.