Determining Buffering Capacity Bio Sciences: pH 10/28/20151

Bellwork How would you convert 327ml to L? What is the volume in L? 10/28/2015 Property of CTE Joint Venture 2

Objectives 1. Explain the plot of pH vs. volume to show buffering capacity of a solution. 2. Graphically represent the difference between a buffered and un-buffered solution. 10/28/2015 Property of CTE Joint Venture 3

Terminology Henderson–Hasselbalch: Used to prepare buffer solutions and to estimate charges on ionizable species in solution, such as amino acid side chains in proteins 10/28/2015 Property of CTE Joint Venture 4

Determining Buffer Capacity Lab, Introduction and Background We will be comparing pH changes of a buffered vs. un-buffered solution. Normally buffering capacity is calculated using the Henderson– Hasselbalch equation: “Used to prepare buffer solutions and to estimate charges on ionizable species in solution, such as amino acid side chains in proteins” 10/28/2015 Property of CTE Joint Venture 5

Determining Buffer Capacity Lab, Objectives I. Explain the plot of pH vs. volume to show buffering capacity of a solution. II. Graphically represent the difference between a buffered and un-buffered solution. 10/28/2015 Property of CTE Joint Venture 6

Determining Buffer Capacity Lab, Tips Read all procedure and double check with partner. Carefully count drops dispensed from NaOH. Volume NaOH is additive, so amount should increase in table with each drop If unsure ASK! 10/28/2015 Property of CTE Joint Venture 7

Closure Find another group and compare your buffered and un-buffered graphs to their. Do you have similar shaped graph, if no how do they differ.? Are your buffering capacities with in 10% of each other? If no, purpose one (1) reason why. 10/28/2015 Property of CTE Joint Venture 8