Chapter 15 Acid Base Titration Ph Section 2 Answers

Chapter 15 Acid Base Titration Ph Section 2 Answers Chapter 15 AcidBase Titration pH Section 2 Answers I This document provides answers and explanations to the questions in the second part of Chapter 15 AcidBase Titration focusing on pH The chapter covers the fundamentals of acid base titration focusing on the application of pH measurements to track the progress of a titration II Key Concepts Titration A technique used to determine the concentration of an unknown solution by reacting it with a solution of known concentration the titrant AcidBase Titration A specific type of titration involving the reaction of an acid and a base pH A measure of the acidity or basicity of a solution expressed on a scale from 0 to 14 Equivalence Point The point in a titration where the moles of acid and base are stoichiometrically equivalent pH Curve A graph that plots the pH of a solution against the volume of titrant added Indicators Substances that change color depending on the pH of the solution used to visually identify the equivalence point III Practice Problems 1 What is the pH of a solution prepared by dissolving 010 mol of HCl in enough water to make 10 L of solution Answer HCl is a strong acid meaning it completely dissociates in water Therefore the concentration of H ions in the solution will be 010 M Using the formula pH logH We can calculate the pH 2 pH log010 10 Therefore the pH of the solution is 10 2 A 250 mL sample of 0100 M NaOH is titrated with 0150 M HCl What is the pH of the solution after 100 mL of HCl has been added Answer First calculate the moles of NaOH present initially moles NaOH 0100 molL 0025 L 00025 mol Then calculate the moles of HCl added moles HCl 0150 molL 0010 L 00015 mol The reaction between NaOH and HCl is a neutralization reaction NaOH HCl NaCl H2O Since HCl is the limiting reagent 00015 moles of NaOH will react with 00015 moles of HCl leaving 00010 moles of NaOH unreacted Next calculate the total volume of the solution Total volume 250 mL 100 mL 350 mL 0035 L Now calculate the concentration of NaOH remaining NaOH 00010 mol 0035 L 00286 M Since NaOH is a strong base the concentration of OH ions is equal to the concentration of 3 NaOH OH 00286 M Calculate the pOH pOH logOH log00286 154 Finally calculate the pH using the relationship pH pOH 14 pH 14 pOH 14 154 1246 Therefore the pH of the solution after 100 mL of HCl has been added is 1246 3 What is the equivalence point of a titration of a weak acid with a strong base Answer The equivalence point of a titration of a weak acid with a strong base occurs when the moles of the weak acid and the strong base are equal At this point the solution contains the conjugate base of the weak acid Since the conjugate base is a weak base the pH at the equivalence point will be greater than 7 4 Explain how an indicator is used to determine the endpoint of a titration Answer An indicator is a substance that changes color depending on the pH of the solution By selecting an indicator with a color change range near the equivalence point of the titration the endpoint can be visually identified The endpoint is the point where the indicator changes color which approximates the equivalence point 5 Draw a typical pH curve for the titration of a weak acid with a strong base Label the equivalence point the buffer region and the initial pH 4 Answer A typical pH curve for the titration of a weak acid with a strong base will have the following characteristics Initial pH The pH will be relatively low due to the presence of the weak acid Buffer region As the strong base is added the weak acid will react to form its conjugate base creating a buffer solution This region will show a gradual increase in pH with added base Equivalence point The point at which the moles of weak acid and strong base are equal leading to a sharp increase in pH The equivalence point will be greater than 7 Beyond the equivalence point After the equivalence point the pH will continue to increase rapidly as the excess strong base dominates the solution IV Conclusion Understanding the relationship between pH acidbase reactions and titration techniques is crucial for performing accurate chemical analysis By mastering the concepts discussed in this chapter you can confidently analyze solutions and determine the concentrations of unknown acids and bases V Further Resources Chemistry textbooks For a more indepth explanation of the topics covered Online resources Numerous websites offer comprehensive explanations and interactive simulations of acidbase titration Laboratory experiments Performing actual titrations in a laboratory setting will provide handson experience and reinforce the theoretical concepts