With this conceptual understanding in their grasp, the students were ready to put some numbers to another water transfer equilibrium analogy. One student volunteered to transfer water from reactants to products and another from products to reactants, each scooping water using a different sized beaker - a 50 mL and a mL beaker Photo 1.Įquilibrium Concept Through Interactive Analogies The reactant bowl was filled half way with blue water and the product bowl was empty at the beginning of the reaction. The transfers were made between two large bowls, labeled as "reactants" and "products". Photo 1: Water transfer equilibrium analogy: notice the transfer beakers are different in size. We can no longer pretend that every reaction goes all the way to completion! Maybe this scared the students more than amused them, but it set the stage with a little humor and a bit of anticipation of what was to come. I likened understanding chemical equilibrium with taking the red pill because you have to open your eyes to the real world of chemistry. With a firm grasp on the concept of equilibrium, the application of the mathematical description of a system was easier for my students to master. The outcome was very positive from my perspective. This year I decided to tackle the conceptual understanding of equilibrium first with three different analogies and a Process Oriented Guided Inquiry Learning POGIL activity before even mentioning the words "equilibrium expression". The equilibrium constant expression for the overall reaction is equal to the product of the equilibrium constant expressions for the individual steps.Įquilibrium concept through interactive analogies Sharon Geyer, Pomfret School, Pomfret CT Share: Equilibrium is a challenging topic for high school chemistry students to understand. All of the substances whose Lewis structures are shown in the figure below, for example, can act as Lewis bases to form complex ions. Any atom, ion, or molecule with at least one empty valence-shell orbitals can be a Lewis acid. By definition, a common ion is an ion that enters the solution from two different sources.ĪP Chemistry : Equilibrium Constant And Reaction QuotientĬalculate the solubility of calcium phosphate in 0. The expression for the solubility product and its value are given by: For comparison purposes later, I need to work out the lead II ion concentration in this saturated solution. Something similar happens whenever you have a sparingly soluble substance. If several salts are present in a system, they all ionize in the solution. The common ion effect suppresses the ionization of a weak base by adding more of an ion that is a product of this equilibrium. Wikimedia Fluoride is more effective than calcium as a common ion because it has a second-power effect on the solubility equilibrium. The common-ion effect is used to describe the effect. The second criteria is easier to test than the first. We start with an aqueous solution of the weak acidin this case, hydrogen sulfide dissolved in water. Reaction Quotient Pogil Answers | latest! Overall, the solubility of the reaction decreases with the. Through the addition of common ions, the solubility of a compound generally decreases due to a shift in equilibrium. The initial value of the reaction quotient is therefore equal to zero. Found 3953 results for: Reaction Quotient Pogil Answers