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At the end of this lab, students should know...
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Q1: How do you prepare a 1 M NaOH solution in the laboratory?
Measure 4 g of solid NaOH and add it to a 125-mL Erlenmeyer flask with 50 mL of deionized water. Stir on a stir plate until dissolved. Once homogeneous, add another 50 mL of deionized water and transfer the solution to a labeled 100-mL polyethylene bottle. Always handle NaOH with caution as it is strongly corrosive.
Q2: What steps are involved in adjusting buffer pH to a target value?
Dissolve the buffer salt in deionized water and calibrate a digital pH meter. Clamp the pH sensor in the buffer solution and allow the reading to stabilize. Slowly add 1 M NaOH or 2 M HCl with pauses between additions to let the pH stabilize. Continue until reaching the target pH, then dilute to final volume with deionized water.
Q3: How should neutral red and riboflavin-binding protein solutions be prepared and stored?
Weigh the solid into a volumetric flask and add deionized water to approximately two-thirds full. Cover with plastic paraffin film and agitate until dissolved. Remove the film and fill to the marked line. Transfer to labeled vials and store both solutions in the refrigerator to maintain stability.
Q4: What personal protective equipment is required when preparing buffer solutions?
Wear a lab coat, chemical splash goggles, and gloves when handling buffer components. Prepare all solutions in a chemical fume hood to protect against vapors and splashes. These precautions are especially important when working with corrosive substances like sodium hydroxide.
Q5: How is a monosodium phosphate buffer brought to its final volume?
After adjusting the pH to the target value, pour the buffer solution into a clean 100-mL volumetric flask. Bring the solution up to the 100-mL mark with deionized water. Seal with plastic paraffin film and invert repeatedly until the solution appears homogeneous throughout.
Q6: What equipment should be set up at each lab station for buffer experiments?
Each pair of students needs a stir plate, pH meter, handheld spectrophotometer, graduated cylinders, beakers, pipettes, cuvettes, and a magnetic stir bar. Additionally, set out calibration buffers, a lab stand with thermometer clamp, micropipettes with tips, and labeled bottles containing prepared buffers in a central location.
Q7: How should prepared buffers and chemical solutions be stored after preparation?
Store prepared buffers in labeled polyethylene bottles capped and placed in the instructor's hood. Keep neutral red and riboflavin-binding protein solutions in labeled vials in the refrigerator. Store 1 M NaOH in a corrosives cabinet. Proper storage maintains solution stability and ensures safety in the laboratory.