CHM-102CHM-102CHM-102

UNCWUNCWUNCW

pH StudypH Study

General Chemistry 101/102General Chemistry 101/102Laboratory ManualLaboratory Manual

University of North Carolina WilmingtonUniversity of North Carolina Wilmington

CHM-102CHM-102CHM-102

UNCWUNCWUNCW

pH StudypH Study• PurposePurpose

To study the differences between strong and weak acids and To study the differences between strong and weak acids and basesbases

To study reactions of water with various salt compoundsTo study reactions of water with various salt compounds To learn the concept of buffering capacityTo learn the concept of buffering capacity

• Safety ConsiderationsSafety Considerations Safety glasses must be worn throughout the entire experiment, Safety glasses must be worn throughout the entire experiment,

even when cleaning glassware to prevent damage due to strong even when cleaning glassware to prevent damage due to strong acids and bases.acids and bases.

Be cautious when using unknown solutions and clean up any Be cautious when using unknown solutions and clean up any spills immediately. Contact with strong acids or bases will affect spills immediately. Contact with strong acids or bases will affect skin and create holes in clothing. Wash the affected area skin and create holes in clothing. Wash the affected area thoroughly if you suspect any skin contact any of unknown thoroughly if you suspect any skin contact any of unknown solutions.solutions.

Flush all wastes down the drain with plenty of water.Flush all wastes down the drain with plenty of water.

CHM-102CHM-102CHM-102

UNCWUNCWUNCW

pH StudypH Study

• ProcedureProcedure Connect the Tablet computer, Microlab unit, and the Connect the Tablet computer, Microlab unit, and the

pH electrode as shown in the illustration below.pH electrode as shown in the illustration below.

CHM-102CHM-102CHM-102

UNCWUNCWUNCW

pH StudypH Study

• ProcedureProcedure To begin determining pH measurements on the computer, click To begin determining pH measurements on the computer, click

on the Applications folder, and select the Microlab prompt. on the Applications folder, and select the Microlab prompt. Then double click on the “pH Titrations” prompt as shown Then double click on the “pH Titrations” prompt as shown below.below.

CHM-102CHM-102CHM-102

UNCWUNCWUNCW

pH StudypH Study

• ProcedureProcedure Click on the experiment entitled “pH Acid-Base – Click on the experiment entitled “pH Acid-Base –

Temperature Manual Titration”, as shown below.Temperature Manual Titration”, as shown below.

CHM-102CHM-102CHM-102

UNCWUNCWUNCW

pH StudypH Study

• ProcedureProcedure

Remove the pH electrode from the pH =7 Remove the pH electrode from the pH =7 buffer and place in a beaker of DI water. buffer and place in a beaker of DI water. Use this beaker to store the pH electrode Use this beaker to store the pH electrode between sample measurements. between sample measurements.

Rinse the pH electrode with DI water from a Rinse the pH electrode with DI water from a squeeze bottle, letting the water run into a squeeze bottle, letting the water run into a smaller beaker designated for waste. Dab smaller beaker designated for waste. Dab the end of the electrode with a Kimwipe and the end of the electrode with a Kimwipe and place the electrode into your sample place the electrode into your sample solution. solution.

pH values will be displayed in the lower right pH values will be displayed in the lower right hand corner of the screen. Record these hand corner of the screen. Record these values on your data sheet upon each pH values on your data sheet upon each pH determination.determination.

When experiment is complete, place the pH When experiment is complete, place the pH electrode back into the pH=7 buffer solution.electrode back into the pH=7 buffer solution.