Solutions, Acids and Bases Modern Chemistry

Solution Solution – a homogeneous mixture of a solute and a solvent. soluble - capable of being dissolved Solute – the chemical that is dissolved Solvent – the substance it is dissolved in Ex.) Salt in water Different types depend on state of solute/solvents: Solid-liquid Liquid-liquid Gas-liquid Liquid-gas Solid-solid Gas-gas

Mixture types Solutions Colloids Homogenous Smallest particle size Does not separate on standing Does not separate by filtration Does not scatter light Colloids Heterogeneous Medium particle size Do not separate on standing Cannot be separated by filtration Scatters light

Mixtures cont. Suspensions Heterogeneous Largest particle size Particles settle out Can be separated by filtration May scatter light, but are not transparent

A substance that dissolves in water to give a solution that conducts electric current is called an electrolyte. Any soluble ionic compound, such as sodium chloride, NaCl, is an electrolyte.

Do all compounds dissolve as well as others? No Solubility - Maximum amount of solute that can dissolve in a given amount of solvent at a given temperature

Factors affecting solubility 1. “Like dissolves like” Polar solvents – dissolve ionic/polar solutes Nonpolar solvents – dissolve nonpolar solutes 2. Pressure No impact on solid-liquid solutions For gas-liquid solutions,  P  Solubility 3. Temperature Solid-liquid solutions, T Solubility Gas- liquid solutions, T Solubility

Speed of solution formation Impacted by: 1. surface area 2. agitation 3. temperature

Heat of solution Energy change when a solution forms Exothermic – releases energy (hot) Endothermic – absorbs energy (cold)

Once a solution forms… Saturated solution – contains the maximum amount of solute Unsaturated solution – contains less than the maximum amount of solute Supersaturated solution – contains more than the maximum amount of solute

Molarity (M) Moles solute Liters solution M = mol L M = Molarity is a standard used to express the concentration of a solution Moles solute Liters solution M = mol L M =

Example molarity problems You have 3.50 L of solution that contains 90.0 mol of sodium chloride, NaCl. What is the molarity of that solution? You have 0.8 L of a 0.5 M HCl solution. How many moles of HCl does this solution contain?

Example molarity problems You have 8.3 L of solution that contains 205 mol of KNO3. What is the molarity of that solution? You have 5.9 mol of HCl in a 1.5 M HCl solution. How many liters do you have?

Dilutions The dilution equation is used to accurately make weaker solutions from stronger solutions by adding water M1V1 = M2V2 Initial Molarity x initial volume = final Molarity x final volume Stock solution Weaker solution

Example If you have 5L of a 12M HCl solution and you want a 3.5M solution, how much water should you add? If you have 2L of a 8.5M HCl solution and you accidentally added 0.65L of distilled water, what is the new molarity?

Green Solution - At which cup did you stop seeing color?   Vanilla Solution At which cup did you stop seeing color? At which cup did you stop smelling vanilla?

Colligative Properties Properties that depend on the concentration of solute particles Freezing Point Depression – add solute and the freezing point goes down Boiling Point Elevation – add solute and the boiling point goes up

What are acids and bases? Special types of solutions with specific properties

Properties of acids and bases Electrolytes Sour taste Produce hydrogen gas when react with metal Corrosive React with a base to make salt + water (called neutralization) Turn litmus red Phenolphthalein - clear Electrolytes Bitter taste Slippery Caustic React with acid to make salt + water (called neutralization) Turn litmus blue Phenolphthalein - pink ACIDS BASES

Common acids Sulfuric Nitric Phosphoric Acetic Hydrochloric

Common Bases Sodium Hydroxide Ammonia Aluminum Hydroxide

Acid Naming Binary acid – contains only two different elements. Ex.) HCl, HF, HBr 1. The name begins with hydro-. 2. The root of the name of the second element follows. 3. The name then ends with the suffix –ic.

Acid Naming (cont.) Oxyacid – is an acid that is a compound of hydrogen, oxygen, and a third element, usually a nonmetal. Ex.) HNO3, H3PO4, H2SO4 Naming: Use the root of the third element and add –ic to the end

Self ionization of pure water Hydronium Hydroxide [H3O+] = [OH-] =1.0 X 10-7 mol/L [H3O+] > [OH-] Acid [H3O+] < [OH-] Base [H3O+] = [OH-] Neutral

How do you find [H3O+] and [OH-]? Use the ionization constant of water Remember… [H3O+] = [OH-] =1.0 X 10-7 mol/L Therefore… [H3O+] X [OH-] =1.0 x 10-14M

Given: Solution of 1.0 x 10-4 M HNO3 What is the hydronium and hydroxide concentrations?

Given: Solution of 1.0 x 10-2 M NaOH What is the hydronium and hydroxide concentrations?

Given: Solution of 1.0 x 10-3.6 M Ca(OH)2 What is the hydronium and hydroxide concentrations?

pH scale Much simpler to manage pH scale 0-6 Acid 7 Neutral 8-14 Base

Calculating pH pH = -log[H+] pOH = -log [OH-] pH + pOH =14

Determine the pH pH 3.0 1.0x10-3 M HCl pH 5.0 1.0x 10-5 M HNO3 pH 4.4 1.0 x 10-4 M NaOH 3.0x 10-2 M KOH pH 3.0 pH 5.0 pH 4.4 pH 10.0 pH 12.48

Indicator A chemical that changes color to help distinguish acids and bases Examples: Phenolphthalein Red cabbage Litmus paper Bromothymol blue

Neutralization Reaction Acidic compounds react with basic compounds neutralizing each other Ex.) NaOH + HCl  NaCl + H2O Baking Powder - NaHCO3 & H2C4H4O6 Antacid