Spring 2012 CH142 1 of 4 Vernier LabPro Instructions VernierSoftware2012 The Vernier LabPro is a versatile data collection interface that can be used in many different ways in the classroom or in the field Today you ll have it connected to a computer and use it to titrate a strong and or weak acid with a strong base 0 1M NaOH The titration can be studied by monitoring changes in pH using a pH electrode The interpretation of the differences in the shape of a titration curve and the information that can be determined from the equivalence point of a titration will enable you to find both the identification and concentration of an acid Start up Turn on the power to the power strip that is connected to the Vernier LabPro a stir plate and a power supply for the DCU pump unit A blinking green light occurs when the Vernier interface receives power The Vernier system will complete a series of 7 beeps as the system completes a self check If no other beeping sounds are given by the interface then the system is ready for use How to Calibrate the Pump Doing this will let you find the volume delivered by the pump per pulse Log in to a lab computer Click on the blue folder to open the Vernier 2011 2012 folder Wait for it to open then double click on pumpcalibration cmbl You ll hear your pump click and a blinking green light will be visible on the Vernier interface Note that the toggle switches on the pump should always be set on computer and DCU for the pump to be computer controlled If prompted with a Sensor Confirmation window click on the blue connect button If the window is not displayed continue on The main calibration window should be activated and the green Collect button will be found in the top menu bar The table on the left side of the screen will record collected data in the appropriate columns The smaller box below the table will count the pulses delivered by the pump The graph will display a green colored signal for each pulse To prime the pump with deionized water find the inlet tubing marked as IN on the pump and submerge the tubing into a deionized water bottle To prevent air bubbles from entering the line make sure that the line is secure and that the opening of the tubing is down below the water surface Put the outlet tubing into an empty small beaker Click on the green Collect button A window will appear that will ask what you would like to do click on Erase and Continue The pump will run for 30 pulses Click on Collect again and then Append to Latest to add another series of 30 pulses It will take about 90 pulses to prime the pump with water Check for bubbles in the tubing If you see large bubbles check your set up and then add another set of pulses If no bubbles are apparent in the lines then continue To calibrate the pump volume in uL delivered by each pulse find the mass of a clean dry weigh vial without its cover Use a clean dry Kimwipe to handle the vial because fingerprints and dirt will add to the mass and result in calibration error Spring 2012 CH142 2 of 4 Set the outlet tubing into the weigh vial and deliver a total of 60 pulses of deionized water Weigh the vial Using the density of water at room temperature 0 9982 g ml at 20C convert the mass of the water delivered to the corresponding volume of water delivered Calculate the volume of water delivered in a single pulse by the pump in uL pulse Remove the inlet tubing from the water and put it into your NaOH bottle Prime the pump with the strong base for at least 90 pulses Be sure that there are no bubbles in the line Quit Logger Pro If asked the following Do you want to save the current file before closing Click on Don t Save You now want to double click on acidbasetitration cmbl How to set up the Titration If prompted by a Sensor Confirmation window click on the blue connect button The new window will show a table displayed on the left side of your screen This will record collected data in columns labeled with color coded headings A small window under the table will display current pH readings The larger graphing window will display your data as it is being recorded The X axis is the volume uL delivered by the pump and is set from 0 to 20 000 uL The Y axis is the sensor output and is set to record pH 0 to12 If necessary the axes may be rescaled at anytime by clicking on the minimum maximum value and typing in the preferred value Click on Data from the top menu and slide down to Clear All Data to clear the window To calibrate the volume X axis use the scroll bar at the bottom of the left hand table to find the Volume uL column and double click on that heading A Calculated Column Options window will appear Go to the displayed Equation box and change ONLY the value in the equation to be the calibrated uL pulse you calculated earlier Click Done NOTE When clearing data and or erasing and continuing between titrations always check that the pump calibration volume pulse volume has not been changed to the default value It should still be set to the volume that you have determined How to calibrate the pH electrode Chose Experiment and then choose Calibrate Sliding to the right choose LabPro 1CH1 Electrode Amplifier The Sensor Calibration window will appear Make sure that the current calibration is set for Electrode Amp pH Sensor Page 1 Click on the Calibrate Now button This is a two buffer point calibration Remove the pH electrode from the electrode storage solution make sure that the blue ring collar is turned to open rinse well with deionized water and place in the pH 4 pink buffer solution Always make sure the ground glass frit is covered by solution and no bubbles are caught in the protective cage Once the volts reading has stabilized type 4 00 into the Reading 1 box and press the Keep button Repeat process to calibrate in pH 7 buffer solution and press the Keep button Press OK Spring 2012 CH142 3 of 4 How to prepare the sample for automated titration Add 50 ml of deionized water to a clean 100 ml beaker Using a 10 0 ml volumetric pipet add 10 0 ml of acid to the water Place the beaker on the stir plate add a stir bar and begin stirring Rinse and dry the pH electrode and carefully place it in the beaker Rest the electrode on the extended portion of the lip of the beaker You want to arrange the beaker so that the stir bar does not hit the electrode Record the starting pH Using the provided clip attach the pump outlet tube …