Chemistry – April 26, 2017 P3 Challenge – The pH of a solution is found to be 8.35. Determine: A) pOH B) [H+] C) [OH–] Get out Acid/Base pH worksheet for HMW check

pH Calculations Four related quantities: pH, pOH, [H+] and [OH-] pH = -log [H+] , pOH = -log [OH-], Kw = [H+] [OH-] = 1 x 10-14 , pOH + pH = 14 Note: the opposite of pH = -log [H+] is [H+] = 10 –pH Calculate the other three quantities for the given information. Then indicate if it is an acidic or basic solution. [H+] = 4.0 x 10-3 M [OH-] = 1.5 x 10-5 M pH = 2.1 pOH = 3.5

Chemistry – April 24, 2017 Today’s Objective – Kinetics Assignment: Rate of Reaction Worksheet Agenda Homework review Reaction progress Rate of reaction / Kinetics Factors that affect rates

Reaction Rate Not all chemical reactions happen at the same rate. Some happen quickly, others take more time, but do eventually occur. Equilibrium constant describes how much product and reactants you will have when all is said and done, but says nothing about how long it takes to get there. Kinetics is the study of how fast a reaction happens. Reaction rate, is defined as the change in concentrations divided by change in time.

Reaction Rate Reactants Products Over the course of a reaction, the concentration of reactants decreases while the concentration of products increases. Reaction rate is defined as the disappearance of reactants or the appearance of products, in molarity.  means final minus initial. [ x ] means the molarity of x a and c are the coefficients of the balanced equation. Usually, only initial rates are reported.

Reaction profile The reaction coordinate tracks the progress of a reaction from reactants to products. Equilibrium is determined by the relative energies of reactants and products. There is a barrier to transformation as bonds have to break and reform. This is the Activation Energy.

Collision Theory Collision theory explains what conditions are necessary for a reaction to happen. In order to react, reactants must 1) collide with each other 2) collide with the proper orientation to create an activated complex 3) collide with enough energy to overcome the activation energy Reaction rate is related to the activation energy. The higher the activation energy, the slower the reaction.

Factors that affect reaction rate 1) Concentration – more chance for reactants to meet and collide Doubling the concentration of a reactant will double the rate 2) Physical state – more chance for reactants to meet and collide A) mixing more mixing = faster rate B) particle size / surface area smaller particles/increased surface area = faster rate

Factors that affect reaction rate 3) Temperature – reactants must have enough energy Increases average particle speed and number of collisions = faster rate 4) Catalyst – decreases the activation energy More reactants will have the needed energy Ways to speed up a reaction: Stir it, Crush it, Heat it.

Exit Slip - Homework Exit Slip: You want to make Koolaid using the sugar you have on hand that is in the form of sugar cubes. Suggest three ways you can speed up the dissolution of sugar cubes into water. What’s Due? (Pending assignments to complete.) Rate of Reaction worksheet What’s Next? (How to prepare for the next day) Read p496 - 520