Mixtures (Solutions) Ms. Rosendo

characteristics of these Mixtures a combination of two or more substances that do not combine chemically, but remain the same individual substances; can be separated by physical means Two types: Heterogeneous Homogeneous Based on the prefixes “hetero” and “homo,” what do you think are characteristics of these two types of mixtures?

Heterogeneous Mixture “Hetero” means different consists of visibly different substances or phases (solid, liquid, gas) a suspension is a special type of heterogeneous mixture of larger particles that eventually settle Example: Notice the visibly different substances Trail Mix

Homogeneous Mixture “Homo” means the same has the same uniform appearance and composition throughout; maintain one phase (solid, liquid, gas) Commonly referred to as solutions Example: Notice the uniform appearance Salt Water

Solution a mixture of two or more substances that is identical throughout can be physically separated composed of solutes and solvents Salt water is considered a solution. How can it be physically separated? the substance in the smallest amount and the one that dissolves in the solvent the substance in the larger amount that dissolves the solute Iced Tea Mix (solute) Water (solvent) Iced Tea (solution) Colloids (milk, fog, jello) are considered solutions

Concentration the amount of solute dissolved in a solvent at a given temperature described as dilute if it has a low concentration of solute described as saturated if it has a high concentration of described as supersaturated if contains more dissolved solute than normally possible

Solubility the amount of solute that dissolves in a certain amount of a solvent at a given temperature and pressure to produce a saturated solution influenced by: What do we call things that are not soluble? Temperature Pressure Solids increased temperature causes them to be more soluble and vice versa Gases increased temperature causes them to be less soluble and vice versa Ex. Iced Coffee Solids increased pressure has no effect on solubility Gases increased pressure causes them to be more soluble and vice versa Ex. Soda, “The Bends”

Concentration of Solute The amount of solute in a solution is given by its concentration. Molarity ( M ) = moles solute liters of solution

PROBLEM: Dissolve 5.00 g of NiCl2 in enough water to make 250 mL of solution. Calculate the Molarity. Step 1: Calculate moles of NiCl2 Step 2: Calculate Molarity [NiCl2] = 0.154 M

moles = M•V USING MOLARITY Step 1: Change mL to L. What mass of oxalic acid, H2C2O4, is required to make 250. mL of a 0.0500 M solution? moles = M•V Step 1: Change mL to L. 250 mL * 1L/1000mL = 0.250 L Step 2: Calculate. Moles = (0.0500 mol/L) (0.250 L) = 0.0125 moles Step 3: Convert moles to grams. (0.0125 mol)(90.00 g/mol) = 1.13 g

Learning Check How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution? 1) 12 g 2) 48 g 3) 300 g

Two Other Concentration Units MOLALITY, m m of solution = mol solute kilograms solvent % by mass grams solute grams solution % by mass =

Calculating Concentrations Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g of H2O. Calculate molality and % by mass of ethylene glycol.

pH Scale ranges from 0-14 Acids  found between a number close to 0 & 7 Bases  found between 7 & 14 Neutral  7 measures the acidity or basicity of a solution by focusing on the concentration of hydrogen ions (H+) in a solution equals the negative log of the concentration of H+ NaOH (sodium hydroxide) Tums (antacid tablets) Pure Water (distilled) Soda HCl (hydrochloric acid)