CHEM 1001 Lab 2: Solutions and Dilutions

Measuring Mass

• Distinction between scales (measurements based on a calibrated range) and balances (instruments for measuring mass).
• Mass refers to the amount of matter in an object, whereas weight measures the gravitational force on that object.
• Mass remains constant regardless of location, while weight varies with gravitational influence (e.g., rhinoceros on Earth vs. Moon).
• Balances are classified into mechanical (useful parts) and electronic (minimal moving parts).
• Further classification of balances into rough/top-loading (sensitivity ±0.01g) and analytical (sensitivity ±0.0001g).
• Lab involves measuring mass using various balances; instructor demonstrates proper handling.

Preparing Solutions

• Solution is a homogeneous mixture of solute (lesser amount) and solvent (greater amount) with uniform properties.
• Concentration expressed by the formula C = m/V (mass of solute per volume of solvent).
• % (w/v) concentration notation represents grams of solute per 100 mL of solvent.
• Example: 1% (w/v) solution = 1g solute in 100mL solvent.

Solutions to Prepare

• Solution 1: 0.10% (w/v), 100 mL, equivalent to 0.10 g/100 mL.
• Solution 2: 0.1775% (w/v), 50 mL, equivalent to 0.1775 g/100 mL.
• Solution 3: 0.0585% (w/v), 250 mL, equivalent to 0.0585 g/100 mL.

Preparation Procedure

• Calculations for solute amounts performed by the instructor before class begins.
• Rinse all glassware with distilled water to avoid contamination.
• Measure out the solute on an analytical balance using a weigh boat, then transfer to a beaker.
• Add approximately half the required solvent, stir until completely dissolved.
• Transfer contents to a volumetric flask using the quantitative transfer technique, ensuring no residue is left.
• Fill the volumetric flask to the etched line with solvent and mix by gentle inversion.
• Label a 50 mL centrifuge tube with solute type, solvent, concentration, date, and name before transferring solution.
• Repeat the procedure for each solution required for future labs.

Waste Disposal

• Dispose of liquid waste in the designated container within the fume hood.
• Dispose of weigh boats in the large biohazard container.

This quiz focuses on the essential concepts of measuring mass, specifically distinguishing between scales and balances in a chemistry lab setting. Understand the fundamental terms that are crucial for conducting experiments with solutions and dilutions. Test your knowledge and prepare for practical applications in lab work.