The Physical Sciences Initiative. Chemistry Inservice D A T A L O G G I N G. Heat of Reaction. for. Graphic Calculator & Computer

Transcription

1 The Physical Sciences Initiative Chemistry Inservice D A T A L O G G I N G Heat of Reaction for Graphic Calculator & Computer Nov

2 Heat of Reaction. A Styrofoam cup calorimeter is used in this experiment to measure the heat released by the reaction between 1.0 M HCl solution and 1.0 M NaOH solution. For purposes of this experiment, you may assume that the heat loss to the calorimeter and the surrounding air is negligible. Solutions of aqueous sodium hydroxide and hydrochloric acid react to form water and aqueous sodium chloride as shown below. Na + (aq) + OH (aq) + H + (aq) ) + Cl (aq) H2O(l) + Na + (aq) + Cl (aq) H =? Apparatus and Chemicals 1. CBL 2 datalogger with DataMate Program 2. TI-83 Graphing Calculator 3. Temperature Sensor 4. Styrofoam cup cm 3 beaker 6. Stand and clamp cm M HCl cm M NaOH 9. Graduated Cylinder 10. Stirring rod 2

3 Setting up the calculator and datalogger Place the Calculator in the cradle. Place the CBL 2 datalogger on the underside of the cradle. Place the Temperature Sensor probe in channel 1 of the CBL 2. Connect the Calculator to the CBL 2 using the small connection lead. Make sure the lead is pressed fully home. (The connection ports are at the bottom of the Calculator and CBL 2). If the sensor is connected before the Calculator is turned on, it will be automatically detected. Selecting the Sensor and the type of data collection The Sensor Menu Data Collection Mode Menu 3

4 Turn on the Calculator. Press APPS (blue key). From the menu that appears select the Datamate program by pressing the appropriate number. Press CLEAR ( Removes any data present from previous experiments). Channel 1 should show the Temperature Sensor is attached. If the Temperature Sensor is not detected in channel 1, then it must be selected from the sensor menu. Press 1 Setup. Press ENTER at channel 1 and select the Sensor from the list. Select the units (C) by pressing the appropriate button. Press 1 OK. You must now decide on the type of data collection you require. Press 1 Setup. Scroll up using the arrow key to select Mode from the menu. Press ENTER. Press 2 Time graph. Select CHANGE TIME SETTINGS Type in 1 second as the chosen time between samples, Press ENTER. Type in 60 as the chosen number of samples Press ENTER. again. Press 1 OK twice. The CBL 2 and Calculator are now ready for the experiment. 4

5 Figure 1 Procedure for the Experiment and collecting the Data Set up the apparatus as shown in Figure 1. Measure out 50.0 cm 3 of 1.0 M HCl into the Styrofoam cup Lower the Temperature Sensor into the solution. Measure out 50.0 cm M NaOH into a graduated cylinder. Monitor temperature (in C) on the calculator screen. It may take several seconds for the Temperature Sensor to equilibrate at the temperature of the solution. Select START to begin data collection Allow three or four readings at the same temperature to be recorded. Add the NaOH solution to the Styrofoam cup. Using the stirring rod, stir continuously until the temperature has maximized and then begun to drop. Data collection will stop after 60 seconds 5

6 To confirm the initial (t1) and final (t2) values you recorded earlier, examine the data points along the curve on the displayed graph. As you move the cursor right or left, the time (X) and temperature (Y) values of each data point are displayed below the graph. Rinse and dry the Temperature Probe, Styrofoam cup, and Stirring Rod. Dispose of the solution as directed by your instructor. Analysing Data Once the experiment has finished the graph of the results is displayed on the screen. Pressing ENTER (followed if necessary by 1) will bring you back to the Main Menu Screen, so that the data may be analysed. The Main Menu The Analyse Menu 6

7 To find the Maximum and Minimum Temperature for this experiment. Choose 4 Analyse on the Main Menu screen Choose 4 Statistics on the Analyse Options screen Select the Left Boundary by pressing enter Use the Arrow keys to move to the Right Boundary. Press ENTER. The Minimum and Maximum temperature values recorded are displayed. Calculating Heat of Reaction Determine the temperature change, t = t2 t1, for the reaction. Calculate the heat released by the reaction, H, by using the formula H = m C t (C = 4.18 kj/kg C;---- m is the mass in kg of liquid taken to be water - which has absorbed heat. Density = 1g/cm 3 ) Calculate moles of NaOH used in the reaction by using the molarity, M, of the NaOH and its volume, L. Use the results of Step 2 and Step 3 calculations to determine the amount of heat per mole of NaOH released in the reaction. Apply the sign convention to obtain the heat of reaction 7

8 Data and Calculations 1. Mass (total) of solution, m Kg 2. Final temperature, t 2 o C 3. Initial temperature, t 1 o C 4. Change in temperature, t o C 5. Heat, H kj 6. Moles of NaOH mol 7. H/mol kj/mol 8. Experimental value kj/mol 9. Accepted value kj/mol 10. Percent error % 8

9 Transferring Data from the Calculator to a Computer Connect the Calculator to the Computer using the grey Graph link cable. On the Computer Click on the icon for Graphical Analysis. Choose File and select Import from TI calculator Select Port From the window choose COM 1 Click O.K On the Calculator Turn off the Calculator by pressing 2 nd. and Off Turn the computer back on. Press 2 nd Link Press 4 to select Lists Select L1.by pressing ENTER. Press the down arrow and press ENTER. to select L2. Move the cursor to the top and press the right Arrow to select Transmit Press 1 or ENTER. to Transmit data Your data should now appear on the Graphical Analysis screen. You can Analyse this data following the analysing instructions of LoggerPro found in the Computer version of these experiments. 9

10 Heat of Reaction A Styrofoam cup calorimeter is used in this experiment to measure the heat released by the reaction between 1.0 M HCl solution and 1.0 M NaOH solution. For purposes of this experiment, you may assume that the heat loss to the calorimeter and the surrounding air is negligible. Solutions of aqueous sodium hydroxide and hydrochloric acid react to form water and aqueous sodium chloride as shown below. Na + (aq) + OH (aq) + H + (aq) ) + Cl (aq) H2O(l) + Na + (aq) + Cl (aq) Apparatus and Chemicals 1. LabPro data logger. H =? 2. PC with Logger Pro software installed 3. USB port connecting cable 4. Temperature Sensor 5. Styrofoam cup cm 3 beaker 7. Stand and clamp cm M HCl cm M NaOH 10. Graduated Cylinder 11. Stirring rod THE DATALOGGER Setting up the Data logger and PC Connect LabPro to the computer via the USB cable.you may need to slide the plastic window on the side of the data logger to access the port. Connect the Temperature Sensor to channel 1 on the LabPro Attach the power lead to LabPro and turn it on. 10

11 THE COMPUTER Double click on the Logger Pro icon on the desktop. If there is no icon displayed the program is found by clicking Start followed by Programs, followed by Vernier Software and finally Logger Pro. The program should detect the Temperature Sensor and the window below is displayed. If the program does not detect the Sensors you are greeted with a welcome page. Follow the instructions to open the prepared experiments. Click on File, select Open. Double Click on Chemistry with Computers. Double Click on Exp. 01 Endo -Exothermic. Click on Stainless Steel Temp. The screen is divided into three main areas. Graph Window here data points are plotted as soon as they are recorded. Meter Window this shows the reading recorded by the current sensors. Table Window Entries are recorded here in columns.(similar to Spreadsheet) Click on the Setup Collection icon at the top of the screen Set the data collection for Real Time Collect Set the Experiment Time for 60 seconds at a rate of one sample every second 11

12 You are now ready to collect data Procedure for the Experiment and Collecting the Data. Set up the apparatus as shown in Figure 1 Measure out 50.0 cm 3 of 1.0 M HCl into the Styrofoam cup. Lower the Temperature Sensor into the solution. Measure out 50.0 cm 3 of 1.0 M NaOH into a graduated cylinder.. Click on Collect at the top of the screen. Allow three or four readings at the same temperature to be recorded. Add the NaOH solution to the Styrofoam cup. Using the stirring rod, stir continuously until the temperature has maximized and then begun to drop. 12

13 Readings taken every second are being logged and plotted on a graph of Temperature against Time. Analysing the Data Click on the Graph Window where the Data points h ave been plotted. Click on the Autoscale icon at the top of the screen. Click on Analyse and choose Statistics A statistic box will appear containing Max. and Min. Temperatures From this data you can record the change in Temperature Click on Analyse from the top toolbar and select Examine Data values can be read.as you move along the graph. Rinse and dry the Temperature sensors Styrofoam cup and Stirring rod. Dispose of the solutions as directed by your instructor. Calculating Heat of Reaction 1.Determine the temperature change, t = t2 t1, for the reaction. 2.Calculate the heat released by the reaction, H, by using the formula H = C m t: (C = 4.18 kj/kg C;---- m is the mass in kg of liquid taken to be water - which has absorbed heat. Density = 1g/cm 3 ) 3.Calculate moles of NaOH used in the reaction by using the molarity, M, of the NaOH and its volume, L. 4.Use the results of Step 2 and Step 3 calculations to determine the amount of heat per mole of NaOH released in the reaction. 13

14 5.Apply the sign convention to obtain the heat of reaction Data and Calculations 1. Mass (total) of solution, m Kg 2. Final temperature, t2 o C 3. Initial temperature, t1 o C 4. Change in temperature, t o C 5. Heat, H kj 6. Moles of NaOH mol 7. H /mol kj/mol 8. Experimental value kj/mol 9. Accepted value kj/mol 10. Percent error % 14