PREPARING SOLUTIONS AND REAGENTS

Chemical Solutions (aqueous = water is the solvent) Types of vessels (least to most precise): Beaker Erlennmeyer flask Graduated cylinder Volumetric flask

DEFINITIONS: SOLUTES -- substances that are dissolved SOLVENTS -- substance in which solutes are dissolved (usually water) AMOUNT -- how much

Goals Make solutions Dilute solutions Convert between different concentrations of solutions

Facts of Life Mass is measured in Grams, mg, μg 1g = 1000mg = 1,000,000µg Volume is measured in liters, mL, μL 1L = 1000mL = 1,000,000 μL Density of water is 1 g / mL

Facts of life (cont’d) Concentration means: amount of solute in a volume of solution

? = 0.63 mg, so the concentration is 0.63 mg/mL Each star represents 1 mg of NaCl. What is the total amount of NaCl in the tube? _____ What is the concentration of NaCl in the tube (in mg/mL)? _____   5 mg = ? 8 mL 1 mL 1mL x 5mg ————— = ? mg 8mL ? = 0.63 mg, so the concentration is 0.63 mg/mL 8 mL

Percent Solutions Per means “for every one” Cent means 100 Example: a 5% sugar solution has 5 grams of sugar for 100g of solution, or 5g 100 g of water = 100 mL, and the 100mL solution is mostly water.

Procedure 1. Measure out 7.5g of lemonade and put in 75mL of water. (This is the solution) 2. Measure out 2.25g of lemonade and put it in 75mL of water. (This is the 30% dilution)

Questions 1. What was the solvent in the lab? 2. What was the solute in the lab? 3. Independent variable? 4. Dependent variable? 5. Constants?