Solutions Homogeneous mixtures of 2 or more substances Can be: Solid Sterling Silver Gas Air Liquid **Used most frequently in chemistry**

Solution Components: Solvent Solute the component present in the greatest amount all other components dissolved in solvent

Aqueous Solutions Solvent Solute Whatever is dissolved in the water In chemical equations, denoted as aqueous (aq)

Universal solvent POLAR molecule Oxygen has higher electronegativity than Hydrogen so it pulls the bonded electrons closer to it giving it a partial negative charge δ+ δ-

How things dissolve in 1) Ionic Compounds (Salts) Ionic compounds dissociate into component ions & surrounded by water molecules (solvated) Compound of cation & anion (normally metal + nonmetal)

How things dissolve in 2) Covalent Compounds (Molecules) Compounds of nonmetals Molecular substances dissolve without forming ions - water molecules surround molecules *EXCEPTION: Acids/Bases

How things dissolve in 3) Acids & Bases Form IONS in solution Acids usually have Hydrogen at start of chemical formula or contains COOH group

STRONG ACID/BASESWEAK ACID/BASES Completely dissociate Partially dissociate

Electrolyte & Nonelectrolyte Electrolyte: a substance whose aqueous solutions contains ions Nonelectrolyte: a substance whose aqueous solutions does not contain ions Ions are able to carry electrical charge to and from electrodes— conduct electricity No ions to carry electrical charge to and from electrodes— do not conduct electricity

Nonelectrolyte Strong electrolyte Weak electrolyte

Identifying Electrolytes Strong electrolyteWeak electrolyteNonelectrolyte Ionic Molecular AllNone Strong Acids Weak Acids/Bases All other compounds Strong AcidsStrong Bases HCl HBr HI HClO3 HClO4 HNO3 H2SO4 (first proton) Group 1A metal Hydroxides Heavy Group 2A Hydroxides [Ca(OH)2, Sr(OH)2, Ba(OH)2]

Equations of Strong/Weak Electrolytes HCl (aq) H + (aq) + Cl - (aq) CH 3 COOH (aq) H + (aq) + CH 3 COO - (aq)  Half arrows in opposite direction indicate chemical equilibrium- forward reaction is equal to rate of backward reaction In this case, molecules are ionizing and ions are recombining to form molecules

BaF 2 *water molecules not shown for simplicity* Electrolyte or Nonelectrolyte? Strong or Weak? Ions present? - Ba 2+ F-F-

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Electrolyte or Nonelectrolyte? Strong or Weak? Solution of: MgCl 2 KCl K 2 SO 4 *water molecules not shown for simplicity* Extra Credit: Write the correctly balanced electrolyte equation that the picture could represent.

Precipitate Reactions Reaction in which two aqueous solutions produce an insoluble product called a precipitate

KI (aq) + Pb(NO 3 ) 2 (aq)  KNO3 (aq) + PbI 2 (s)

Solubility Rules Soluble Compounds Contain: C 2 H 3 O 2 -, CH 3 COO - NH 4 + NO 3 - CN - ClO - ClO 2 - ClO 3 - ClO 4 - Br - Cl - I - SO 4 -2 Common Exceptions: None Compounds of Ag +, Pb 2+, Hg 2 +2 Compounds of Sr +2, Ba +2, Pb +2, Hg 2 +2 Insoluble Compounds Contain: CO 3 -2 PO 4 -3 CrO 4 -2 Cr 2 O 7 -2 OH - S -2 Common Exceptions: Compounds of NH 4 + & Alkali Metal Compounds of NH 4 + Alkali Metal, Ca +2, Sr +2, and Ba +2

Ag 2 SO 4 (aq) + Na(NO 3 ) (aq)  

Ionic Equations & Spectator Ions 2KI(aq) + Pb(NO 3 ) 2 (aq)  PbI 2 (s) + 2KNO 3 (aq) Chemical Equation: shows chemical formulas without indicating ionic character Complete Ionic Equation: all soluble strong electrolytes shown as ions 2K + (aq) + 2I - (aq) + Pb 2+ (aq) +2NO 3 - (aq)  PbI 2 (s) +2K + (aq) +2NO 3 - (aq) Net Ionic Equation: only the ions and compounds directly involved in reaction shown Ions that appear in identical form on both sides of ionic equation are called spectator ions - they don’t play a role in the reaction 2I - (aq) + Pb 2+ (aq)  PbI 2 (s)

Which ions if any, are spectator ions in this reaction? NaCl(aq) + AgNO 3 (aq)  AgCl(s) + NaNO 3 (aq)

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Concentration of Solutions Concentration: amount of solute dissolved in given quantity of solvent or quantity of solution

Molarity (M) Way to measure the concentration of a solution Number of moles of solute in a liter of solution moles solute volume of soln (L) Molarity = mol V M =

Practice! Calculate the molarity of a solution made by dissolving 23.4g of sodium sulfate in enough water to form 125mL of solution.

Converting between molarity, moles & volume mol V M =

Practice! A solution of HNO 3 has a concentration of 0.200M; how many moles does a 2.0L solution contain?

Making Solutions Mass appropriate amount of solute Add to container (volumetric flask, beaker, Erlenmeyer flask etc) Add water, swirl to dissolve Continue to add water until required volume of solution reached

Dilution Process of making a lower concentration solution from a higher concentrated solution.

Dilution **Since you’re not changing the amount of solute:** Mol of solute before dilution = mol of solute after dilution mol V M = M 1 V 1 =M 2 V 2

Practice! How many milliliters of 3.0M H 2 SO 4 are needed to make 450mL of 0.10 M H 2 SO 4 ?