מדידה מדעית ומיומנויות מעבדה
At the end of this lab, students should know...
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Q1: What personal protective equipment should you wear when preparing a laboratory?
Wear a lab coat, chemical splash goggles, and gloves to protect yourself from chemical hazards during solution preparation. These items shield your skin, eyes, and clothing from potential splashes or spills when handling reagents like erythrosin B dye and other chemicals throughout the experiment.
Q2: How do you prepare a 1.5 × 10⁻⁵ M erythrosin B solution?
Weigh 0.0066 g of erythrosin B on an analytical balance and transfer it to a 250-mL Erlenmeyer flask. Add 200 mL of deionized water, stir until homogeneous, then transfer to a 500-mL volumetric flask and fill to the line with deionized water. Invert several times to ensure thorough mixing and proper concentration.
Q3: Why is a volumetric flask used when preparing solutions?
A volumetric flask ensures precise solution concentration by allowing you to fill to an exact volume mark with accuracy. This precision is critical for reproducible experimental results, especially when preparing dilute solutions like erythrosin B dye at specific molarity concentrations for consistent lab outcomes.
Q4: What glassware and equipment should be set up at each student lab station?
Each station requires beakers (50, 100, 250, 400, 600 mL), a 500-mL filter flask, Büchner funnel, graduated cylinders, volumetric pipettes, volumetric flask, watch glass, stirring rod, rubber policeman, and filter paper. Additional items include tubing, ruler, rubber adapter, stopper, string, and disposable pipette for independent student work.
Q5: How should you store the prepared erythrosin B dye solution?
Transfer the solution into a labeled 500-mL squeeze bottle indicating its concentration and store it on a mat in the hood. This storage method protects the solution from light exposure and contamination while keeping it accessible for student use during the experiment.
Q6: What materials should be prepared for student access during the lab?
Place acetone in an accessible area, with approximately 40 mL per student. Set out weigh boats, scoops, and sand (about 3 g per student) next to a balance. Position an organic waste container in a central hood for safe disposal of chemical materials used throughout the experiment.