Experimental Chemistry
What to know
Experimental chemistry covers lab technique, measurement, data analysis, and safety. Understand significant figures and precision vs accuracy; know how to read burets, graduated cylinders, and balances to the correct precision. Distinguish random error from systematic error. Recognize common separation techniques-filtration (insoluble solid from liquid), distillation (boiling-point differences), chromatography (differential affinity), and extraction.
Know standard lab procedures: titration (using a buret and indicator to find concentration), gravimetric analysis (precipitate, filter, dry, weigh), and calorimetry. Identify glassware by purpose-volumetric flasks for precise dilution, graduated cylinders for approximate volumes, pipets for exact aliquots. Understand safety: goggles, fume hoods for volatile/toxic substances, never adding water to concentrated acid (add acid to water), and proper waste handling.
Traps
- Reading a meniscus incorrectly (read the bottom of the curve at eye level).
- Reporting more significant figures than the instrument allows.
- Confusing precision (repeatability) with accuracy (closeness to true value).
- Choosing the wrong separation method for the property difference involved.
Worked example
A 25.0 mL sample of acid is titrated to the endpoint with 20.0 mL of 0.100 M NaOH. Moles NaOH = 0.0200 L × 0.100 = 0.00200 mol. For a 1:1 acid, moles acid = 0.00200; concentration = 0.00200/0.0250 = 0.0800 M. Rule of thumb: moles = M × V (in liters), then divide by the sample volume.