M5

• What is spectrophotometry used for?

  To measure solute concentration in solutions
• Why is spectrophotometry considered powerful?

  It measures light absorption at different wavelengths
• How can you identify dissolved substances in a solution?

  By analyzing light that passes through the solution
• What materials are required for spectrophotometry?

  • Spectrophotometer
  • Cuvette
  • Blank solution
  • Reagents (e.g., Cobalt (II) Crystal chloride)
• What is the first step in preparing samples for spectrophotometry?

  Turn on the spectrophotometer
• Why should you let the spectrophotometer warm up?

  To ensure accurate readings
• What should you do if using reusable cuvettes?

  Clean them thoroughly before use
• What should you avoid touching on the cuvette?

  The clear sides where light passes through
• What is a blank solution in spectrophotometry?

  A control solution with only the solvent
• How should you prepare a blank solution?

  Use the same solvent as the sample
• What is the purpose of wiping the outside of the cuvette?

  To avoid interference from dirt or dust
• Why is it important to use a single wavelength of light?

  To make testing more effective
• What should you do after placing the blank in the spectrophotometer?

  Calibrate the machine with the blank
• What should the needle read when the blank is properly calibrated?

  Zero or 0 on the digital readout
• What indicates that the spectrophotometer is properly calibrated?

  The needle stays at 0 with the blank
• What should you do to measure the absorbance of your sample?

  Place the experimental sample in the machine
• How long should you wait after placing the sample in the machine?

  About 10 seconds
• What should you do if your sample has multiple unknown compounds?

  Repeat readings at 25 nm intervals
• What is transmittance in spectrophotometry?

  Light that passes through the sample
• How is absorbance calculated?

  By measuring how much light is absorbed
• What should you do with absorbance values after measuring?

  Plot them versus the wavelengths on a graph
• How can you identify unknown compounds in your sample?

  By comparing absorbance plots to known compounds
• What is the first step in determining the molar absorption coefficient?

  Select a blank cuvette and place it in the spectrophotometer
• What should you do after measuring the absorbance of a known concentration?

  Record the wavelength at maximum absorbance
• How do you calculate the molar absorption coefficient?

  Using the appropriate equation
• What is the purpose of titration?

  To determine the concentration of a solution
• What is the principle of titration?

  Complete chemical reaction between analyte and titrant
• What is an analyte in titration?

  The solution of unknown concentration
• What is a titrant in titration?

  The solution of known concentration
• What is a standard solution?

  A solution of known concentration
• What is the first step in the titration procedure?

  Pour 20 mL of acid solution into a beaker
• Why should you rinse the pipet with the acid solution?

  To avoid contamination of the sample
• How should you fill the pipet for accurate measurement?

  Have the meniscus at eye level
• What should you add to the Erlenmeyer flask during titration?

  2-3 drops of phenolphthalein indicator
• What is the purpose of clamping the burette?

  To keep it stable during titration
• What should you do after rinsing the burette with base solution?

  Drain and discard the base solution
• Why is it important to ensure no air bubbles in the burette tip?

  To ensure accurate volume measurements
• What should you do when you are close to the end point of titration?

  Use the drop-by-drop approach
• What indicates an over-titrated end point?

  Dark pink color in the solution
• What should be done with the burette before use?

  Rinse it three times with solution