chemistry 1 lab worksheet

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attached is the worksheet for this lab please answer the questions and correct any wrong number/answer thnx.attached is the worksheet for this lab please answer the questions and correct any wrong number/answer thnx.attached is the worksheet for this lab please answer the questions and correct any wrong number/answer thnx.attached is the worksheet for this lab please answer the questions and correct any wrong number/answer thnx.attached is the worksheet for this lab please answer the questions and correct any wrong number/answer thnx.

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Energy of Light: Finding Planck's Constant Laboratory 6 Laboratory Mohammad ID No. Name Course/Section 6 Instructor Partner's Name (if applicable) Date (of Lab Meeting) 10-8-2018 Worksheet PART I. QUALITATIVE PROPERTIES OF LIGHT 1. Consider the equation c = Av. Since c is a constant (speed of light, 3.0 X 108 m/s) what happens to the value of v when is decreased? When I is increased? Explain. The value of when 7 is declared is incrocred The value of when his increarlo vis increasle 2. Now consider the equation E = hv. Here, b is a constant (Planck's constant, 6.626 X 10-4 J-sec. What happens to the Energy (E) when v decreases? When v increases? Explain 3. What color of visible light is associated with high energy? Low energy? What are their relative values of land v? 37 Chemistry 141 Experimental Chemistry PART II. QUANTITATIVE PROPERTIES OF LIGHT 1. Plug in your Energy of Light module into Port A on your MicroLab interface. Turn the interface on (if it's not already) and start the MicroLab program. Open a new experiment by clicking on the "Energy of Light Experiment" icon. 2. Select the 70 nm LED with the rotary switch on the module. Make sure the value knob is all the way counterclockwise. 3. Click on the "Blue 470 nm" line in the box on the left of the screen. 4. Click on the "Start Graphing" button to begin taking data. 5. Slowly rotate the voltage knob on the module in a clockwise direction. If you look at the screen you will see the blue triangle moving to the left as the voltage in- creases. The current will remain constant until the voltage becomes high enough for electrons to flow through the LED. 6. Continue rotating the voltage knob until you see the current (y-axis value) increase rapidly. At this point you should see that the LED is lit on the module. While looking at the LED from the top, decrease the voltage slowly using the knob until the LED is just starting to produce light. (Your eyes are more sensitive than the ammeter measuring the current.) 7. Press the "Mark” button on the module and you should see a dot appear on your graph. This records the activation voltage. 8. If you get a bad mark or a bad set of data, you can select the LED in the software and choose "Erase Data". The program will only erase that LED's data. 9. Sketch your results for your first LED. At what approximate voltage did the current begin to show a dramatic increase? At what voltage did your blue LED begin to light? Which of these should you use as your activation voltage? Explain. 10. Your next LED will be at 502 nm. Do you expect the activation voltage to be higher or lower for that LED? Explain your reasoning, 38 Energy of Light: Finding Planck's Constant Laboratory 6 11. Choose the next LED on the module and in the software and repeat the data gathering steps. 12. The 880 nm and 940 nm LEDs are in the infrared region and you will not be able to see the LED light up visually. If you have a non-iPhone phone, you can watch the LED light up using your camera function. (iPhones have an IR filter.) For these two LEDs, you will need to determine the activation voltage by seeing where the current increases suddenly on the graph. PART III. DATA ANALYSIS 1. Fill in the table below. Hint: Use your equations from the first section to find frequency. A must be in meters for this C = 3 X 10 m/sec 1 eV = 1.60218 x 10-'J Wavelength (x, m) E (J) 1/Wavelength (m') Activation Voltage (V)(eV) 20 Frequency (v, 1/sec) 6.38X10 5.98 X10 14 5.28710 14 4.98 V10 4.69x1d 470 502 568 boz 640 880 1/470 1502 1/568 1602 libuo 1880 1.8 1.75 1.42 1.24 1.08 0.381 2.9 X 10 J 12.8810 2.3 Xlo 2.0X10 1.7810 1,4 x 10-19 -12 3.41X10" 2. Using your data, what generalizations can you make about wavelength and energy? Frequency and energy? 3. Make two graphs in a spreadsheet to find the value of h. The first will be a graph of frequency (v) on the x-axis and energy (E) on the y-axis. The second will be a graph of 1/1 on the x-axis and V, on the y-axis. 39 Chemistry 141 Experimental Chemistry 4. The first graph is essentially a graph of E = hv with E on the y-axis and v on the x-axis. Knowing this, how can you find the value of h? Find the value of h using your method and record here. 5. Calculate the percent error for your value. measured value - accepted value %error = X 100 accepted value 6. The second graph is more difficult to interpret. Open the additional pdf for this lab in D2L and read the section on Analysis and Results to find how to find the value of Planck's constant from your graph. Find the value for h for this second graph and report here. Show your calculations. 7. Calculate and record the percent error for this value of h. 8. Which graph is more accurate? Why do you think that might be? 40
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