CHEM 1125Q 1st Edition Lecture 23Outline of Last Lecture Ch. 16I. Acids, Bases, pH, pOH, Ionization Constants, Percent IonizationOutline of Current Lecture Ch. 16II. Percent IonizationA. Percent IonizationB. 5 Percent RuleIII. pH and KaIV. Weak BasesCurrent LectureII. 5 Percent RuleA. Percent Ionizationa. Percent ionization refers to the amount of acid that is actively reactingin a solutionb. Percent ionization depends on the acid’s original concentrationi. As concentration approaches zero, ionization approached 100 percentii. Percent ionization is proportional to 1/[HA]B. 5 Percent Rulea. The basis of the 5 percent rule is percent ionization, which is the percent of the acid that actually reacts in the systemb. Most weak acids have a percent ionization of less than 5 percent. As a result, when solving for Ka, you can ignore the x in the denominator. For example:i. Ka = x2/(0.5-x)Can be rewritten as:Ka = x2/0.5III. pH and KaA. pH and Kaa. To calculate the pH from Ka, you first use the Ka to solve for x in an equilibrium expression. Then use an ICE table and x to solve for the concentration of H3O+, which you can use to solve for the pHb. You can also use the 5 percent rule in case of a weak acid IV. Weak BasesA. Weak BasesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Since the ionization of a weak base is incomplete, it is treated similarly to a weak acidb. Kb is the base ionization constantc. The larger the Kb, the stronger the based. Weak bases can also use the 5 percent rule, but instead of x representing the concentration of H3O+, it represents the concentration of OH-, which can then be used to solve for pOHe. When a stress is applied to a system at equilibrium, then that system will attempt to counteract the stress by shifting so that it proceeds in the direction that allows for minimal stressB. Stressa. Stress is any of the following:i. The addition of a product or reactantii. The removal of a product or reactantiii. A change in volume, which results in a change in the pressure concentrationiv. A change in temperatureb. Both adding a reactant and removing a product shift a system to the rightc. Both adding a product and removing a reactant shift a system to the leftd. However, this only applies to gaseous or aqueous substances. Adding a solid or a liquid does not result in a change in the
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