2Introduction The Snapshot button is used to capture the screen. Concentration of a Solution (Beer’s Law)IntroductionEach page of this lab that contains the symbolshould be inserted into your journal. After completing a lab page with the snapshot symbol, tap (in the upper right hand corner) to insert the page into your journal.Journals and SnapshotsThe Snapshot button is used to capture the screen.The Journal is where snapshots are stored and viewed.The Share button is used to export or print your journal to turn in your work.Note: You may want to take asnapshot of the first page ofthis lab as a cover page foryour Journal.
3Concentration of a Solution (Beer’s Law) Lab ChallengeThe more concentrated (darker) a colored solution is the more light the solution is absorbing. Given the mathematical relationship between the absorbance of light and the concentration of a solute, determine the concentration of a copper(II) sulfate solution.Copper(II) sulfate solutions
4Concentration of a Solution (Beer’s Law) BackgroundLight is a form of energy that can interact with chemical substances.By examining the wavelength of light (its color) that is absorbed by a chemical substance, the chemicals identity and quantity can be determined.
5Concentration of a Solution (Beer’s Law) ...BackgroundHow a chemical appears to our eyes depends on how light interacts with the substance.Light can be transmitted (passed through), reflected (scattered), or absorbed by a substance.Light transmittedLight reflectedLight absorbedLight absorbed
6Self-Check The green light in the diagram is being ____________. Concentration of a Solution (Beer’s Law)Self-CheckThe green light in the diagram is being ____________.reflectedabsorbedtransmittedtransmogrifiedL6 – text box[ The best choice is… (tap here to enter text) ]
7...Background the concentration of the substance in solution. Concentration of a Solution (Beer’s Law)...Backgroundthe concentration of the substance in solution.The color observed depends on:the chemical nature of the substance.ConcentratedCo(NO3)2NiCl2DiluteK2Cr2O7K2CrO4CuSO4KMnO4the thickness of the sample the light passes through.20 mm path length55 mm path length
8Concentration of a Solution (Beer’s Law) ...BackgroundThese variables are mathematically related to one another in Beer's law:A = ε × b × cA = measured absorbance of the lightε = absorbance coefficient (chemical nature of the substance)b = path distance (thickness of the sample the light passes through)c = concentration of soluteThis equation is a direct relationship (as c increases, A increases) supporting the observation that more concentrated solutions absorb more light and hence look darker.
9Concentration of a Solution (Beer’s Law) Self-CheckBeer's LawAccording to Beer's Law, when you decrease concentration c for a solution, what should result?Absorbance constant is canceled outDistance stays the sameAbsorption increasesDistance increasesAbsorption decreasesA = ε × b × cL6 – text box[ The best choice is… ]
10Concentration of a Solution (Beer’s Law) ...BackgroundIn this experiment, a colorimeter will be used to find the mathematical relationship between the absorbance of orange light (λ=610 nm) and the concentration of copper(II) sulfate.Light Source
11Concentration of a Solution (Beer’s Law) ...BackgroundSince the colorimeter has a fixed path length b, and the experiment only uses copper(II) sulfate (ε) Beer's law (A = ε × b × c ) can be simplified to:A = constant × cThe direct relationship between absorbance and concentration is mathematically represented by a straight line: Y = mX + b.The mathematical relationship (equation) will be determined by graphing measured absorbencies at known concentrations of copper(II) sulfate and fitting the data to a line (calibration curve).The equation of the linear fit will be used to determine the concentration of an "unknown" copper(II) sulfate solution.Y = mX + b
12Always wash hands to remove residue before leaving Concentration of a Solution (Beer’s Law)SafetyFollow all common laboratory safety procedures.Wash your hands with soap and water after handling the solutions, glassware, and equipment.Copper(II) sulfate is hazardous to the environment and should not be disposed of down the drain. Make sure you follow your teacher’s instructions on how to properly dispose of the copper(II) sulfate solutions.BE SAFEAlways wash hands to remove residue before leaving
13Materials and Equipment Concentration of a Solution (Beer’s Law)Materials and EquipmentCollect all of these materials before beginning the lab.ColorimeterSensor extension cableGlass cuvettes with caps (7)Test tubes (6), 20-mm x 150-mmTest tube rackBeakers (2), 100-mL
14Materials and Equipment Concentration of a Solution (Beer’s Law)Materials and EquipmentDistilledWaterAlso collect these additional materials before beginning.Volumetric pipettes (2), 10-mLPipette bulb or pumpNon-abrasive cleaning tissue0.80 M copper(II) sulfate solution, 30 mLUnknown copper(II) sulfate solution, 10 mLDistilled (deionized) water, 30 mL
15Sequencing Challenge Concentration of a Solution (Beer’s Law) The steps to the left are part of the procedure for this lab activity. They are not in the right order. Determine the correct sequence of the steps, then take a snapshot of this page.A. Determine the linear equation for the calibration curve's line of best fit.B. Create a calibration curve by graphing absorbance versus concentration.C. Measure the absorbance of the unknown and determine its concentration using the equation.D. Create five copper(II) sulfate solutions of known concentration and measure the absorbance of each.L6 – text box[ The correct sequence of steps is… ]
16Setup: Calibration Curve Concentration of a Solution (Beer’s Law)Setup: Calibration CurveConnect the colorimeter to the data collection system using a sensor extension cable.Calibrate the colorimeter so that the colorimeter reads an absorbance of 0.0 for distilled water (the solvent).Fill a cuvette with distilled water and cap it.Holding the cuvette by the lid, wipe the outside of the cuvette with a non-abrasive cleaning tissue.Place the cuvette in the colorimeter and close the lid.Push the green calibrate button on the colorimeter.When the green light turns off, the calibration is complete and the cuvette can be removed from the colorimeter.Calibrate Button
17Setup: Calibration Curve Concentration of a Solution (Beer’s Law)Setup: Calibration CurveQ1: Why is it necessary to calibrate the colorimeter using distilled water?L456 – It is necessary to calibrate the colorimeter because… ]
18Setup: Calibration Curve Concentration of a Solution (Beer’s Law)Setup: Calibration CurveQ2: Why do the test tubes need to be dry? What error would be caused by wet test tubes?Measure approximately 30 mL of 0.80 M copper(II) sulfate stock solution into a 100-mL beaker.Measure approximately 30 mL of distilled water into a different 100-mL beaker.Take six clean, dry test tubes and place them in a test tube rack. Label the test tubes: 1, 2, 3, 4, stock, and unknown.L6 – text box[ The test tubes need to be dry… ]
19Setup: Calibration Curve Concentration of a Solution (Beer’s Law)Setup: Calibration CurvePrepare the five standard copper(II) sulfate (CuSO4) solutions listed in the table below. Use one volumetric pipette for the CuSO4 and a different volumetric pipette for the water (H2O).Test Tube #0.80 M CuSO4H2OConcentration (M)12.0 mL8.0 mL0.1624.0 mL6.0 mL0.3236.0 mL4.0 mL0.4848.0 mL2.0 mL0.64stock10.0 mL0 mL0.80Thoroughly mix each solution by gently swirling each test tube.
20Setup: Calibration Curve Concentration of a Solution (Beer’s Law)Setup: Calibration CurveQ3: What will the colorimeter measure? Is this the independent or dependent variable?Fill one cuvette with the 0.16 M CuSO4 solution and cap it. Label the top of the cuvette lid.Continue to fill one cuvette at a time until each solution is in a cuvette, the cap is on, and it is clearly labeled (0.32 M, 0.48 M, 0.64 M, & 0.80 M).L6 – text box[ The colorimeter will measure… ]
21Collect Data: Calibration Curve Concentration of a Solution (Beer’s Law)Collect Data: Calibration CurveUse a non-abrasive cleaning tissue to wipe the outside of the cuvette containing 0.16 M CuSO4 and place the clean cuvette inside the colorimeter.Close the lid of the colorimeter.Q4: Why is it necessary to wipe the outside of the cuvette before you place it in the colorimeter?Q5: Why is it necessary to close the lid of the colorimeter before recording the absorbance?L3 – text box[ Q4: Is it necessary to wipe the outside of the cuvette… ]L6 – text box[ Q5: It is necessary to close the lid of the cuvette… ]
22Concentration of a Solution (Beer’s Law) Tap to start a dataset.Enter the molarity of thefirst sample in theappropriately labeledcolumn.*Tap to record the absorbance of this solution.*To Enter Data into a Table:Tap to open the tool palette.Tap then tap a cell in the data table to highlight it in yellow.Tap to open the Keyboard screen.Table: concentration of CuSO4 Solution and Oragne (610 nm) absorbance
23Concentration of a Solution (Beer’s Law) Remove the 0.16 M cuvette.Wipe the cuvette of the next sample and place it in the colorimeter.Enter the molarity of this sample into the table.Tap to record the absorbance of this solution.Repeat this process for the last three solutions.Tap to stop the collecting of data in this set.Table: concentration of CuSO4 Solution and Oragne (610 nm) absorbance
24Data Analysis: A = constant × c y = m × x Concentration of a Solution (Beer’s Law)Data Analysis:1. Create a linear best fit line of the data collected*.Note: the equation of the best fit line gives:A = constant × cy = m × x*To Apply a Curve Fit:Tap to open the tool palette.Tap to open the Curve Fit screen.Tap the name of the curve fit required.Graph: Oragne (610 nm) Absorbance versus Concentration of CuSO4 Solution
25Concentration of a Solution (Beer’s Law) What is the equation for the line of best fit? Replace y with absorbance (orange 610) and x with concentration.Solve the equation for concentration.4. Enter the equation you determined in question #3 into the data collection system calculator.*Note: SPARK will use this equation to calculate the concentration of your unknown.*To create a Calculation:Tap to open the Experiment Tools screen.Tap CALCULATED DATA to open the calculator.Enter the calculation in the space provided.Tap Measurements to insert collected data into the calculation.L4 – text box[ Equation of the line of best fit: ]L5 – text box[ Concentration: ]
26Setup: Determining Concentration Concentration of a Solution (Beer’s Law)Setup: Determining ConcentrationObtain 10 mL of the unknown copper (II) sulfate solution from your instructor. Put this solution in the test tube labeled "Unknown Concentration".Fill a dry, clean cuvette with the unknown solution, cap it, and label it "unknown".Wipe the outside of the cuvette with a non-abrasive cleaning tissue and place the cuvette in the colorimeter.Close the lid of the colorimeter.
27Collect Data: Concentration of a Solution (Beer’s Law) Change one of the digits displays below to show the calculated concentration of your unknown solution.*Tap to start a data set.Tap to stop the data set.Enter the absorbance and the concentration of the unknown solution in the text box on the top right.*To Change the variable on a digits display:1. Tap to open the tools palette.2. Tap to open the Digits Properties screen.3. Tap the Measurement box and select the desired variable.L4 – text box[ Absorbance: ][ Concentration: ]
28Analysis State Beer's law. Does your data support this statement? Concentration of a Solution (Beer’s Law)AnalysisState Beer's law. Does your data support this statement?L456 – text box[ Beer’s Law states… ]
29Concentration of a Solution (Beer’s Law) AnalysisWould an error occur if some of the cuvettes were dirty? Explain.L456 – text box[ If the cuvettes were dirty… ]
30Concentration of a Solution (Beer’s Law) AnalysisExplain the difference between “absorbance” and “transmittance” of light.L456 – text box[ Absorbance means… ]
31Concentration of a Solution (Beer’s Law) AnalysisWhy is CuSO4 a bluish color? Are colors of light other than blue transmitted?L456 – text box[ A solution of copper (II) sulfate is blue because… ]
32Concentration of a Solution (Beer’s Law) AnalysisWhy was the absorbance of orange (610 nm) light used instead of another color?L456 – text box[ Orange (610 nm) light was used because... ]
33Concentration of a Solution (Beer’s Law) Synthesis1a. A solution of sodium sulfate is clear and colorless, and yet a solution of copper(II) sulfate is blue. Which ions are causing the blue color?1b. Could you use Beer's law to find the concentration of a sodium sulfate solution?L456 – text box[ 1a. Ions that are causing the solution to have a blue color are… ][ 1b. Beer’s Law… ]
34Concentration of a Solution (Beer’s Law) Synthesis2a. What is the minimum number of points needed to create a calibration curve?2b. How many points were used in this experiment? Why?L456 – text box[ 2a. The minimum number of points needed to create a calibration curve is… ][ 2b. This experiment used… ]
35Concentration of a Solution (Beer’s Law) SynthesisOther sensors, such as for pH and conductivity, need to be calibrated, but are able to determine unknown concentrations without creating a calibration curve. Explain how this works.L456 – text box[ The calibration curve in these sensors is… ]
36Concentration of a Solution (Beer’s Law) Multiple ChoiceWhich of the following variables affects the absorbance of light in a solution?The distance the light has to travel through the solution (path length.The amount of solute in each volume (concentration).The wavelength of the light that is interacting with the solution.All of the above variables affect the absorbance of light in a solution.L6 – text box[ The best choice is… ]
37Concentration of a Solution (Beer’s Law) Multiple ChoiceA sample 0.10 M nickel (II) chloride is placed into a cuvette with a 1.00 cm path length. The solution has a measured absorbance of What would you expect the absorbance of a M nickel (II) chloride solution to be?1.02.04.0not enough informationNiCl2 solutionL6 – text box[ The best choice is… ]
38Concentration of a Solution (Beer’s Law) Multiple Choice??What should be in the ‘blank’ cuvette when the colorimeter is calibrated?nothingthe solution with the greatest concentration of solutethe solventa 1.0 M sample of the solutionL6 – text box[ The best choice is… ]
39Concentration of a Solution (Beer’s Law) Multiple ChoiceWhat color of light is transmitted through a copper(II) sulfate solution?redorangegreenblueL6 – text box[ The best choice is… ]
40Multiple Choice How many colors make up white light? 1 3 4 Concentration of a Solution (Beer’s Law)Multiple ChoiceHow many colors make up white light?134more than fivenoneL6 – text box[ The best choice is… ]
41Concentration of a Solution (Beer’s Law) Congratulations!You have completed the lab.Please remember to follow your teacher's instructions for cleaning-up and submitting your lab.Color scheme (RGB values)biology 121, 173, 54chemistry 0 176, 216physics 0, 102, 204earth 204, 102, 0middle 153, 102, 153elementary 255, 51, 0
42References Concentration of a Solution (Beer’s Law) All images were taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons.LIGHT BULBBE SAFECOLORED LIQUIDSVINEGAR (DISTILLED WATER)COLOR SPECTRUMEYEBEAKERBEAKER