Chapter 4

Key Terms: Solution – homogeneous solution Aqueous solution – dissolved in water Solubility – amount of substance that dissolves in a given amount at specific temp Solute – substance being dissolved Solvent – what dissolved in Acid – produces H+ ions (proton donor) Base – produces OH- ions (proton acceptor) Electrolyte – conduct an electric current Molarity – moles of solute per liters of solution Precipitate – solid that forms from reaction Standard solution – solution whose concentration is accurately known

More Key Terms Spectator ions – ions that do not paticipate directly in reaction Net ionic equation – includes only those substances involved directly in the reaction Precipitation reaction – forms a solid through reaction Neutralization reaction – acid-base reaction Titration – delivery from a buret of solution of known concentration into solution being analyzed Indicator – substance that cause color changes Endpoint – where the indicator actually changes color Equivalence point – point where enough has been added to react exactly Oxidation – reduction reaction – transfer of electrons Oxidation states – oxidation numbers = charges

Water Common solvent Water is polar (partial charges on atoms – oxygen is negative, while hydrogen is positive) – “like dissolves like” – dissolves other polar substances – Hydration – positive ends of water attracted to negative ends of ions – Solubility – different levels of solubility for different substances

Aqueous Solutions Every solution has 2 parts – solute & solvent Electrical conductivity is used to characterize solutions – when dissolve do they break up into ions? Strong electrolytesweak electrolytes Ionize completelyionize partially Conduct wellconduct poorly Strong acids & basesweak acids & bases Soluble salts Non electrolytes – dissolve in water but no ions produced

Molarity Represented by M or [ ] (2.0 M NaCl [NaCl] = 2.0) Molarity = moles solute Liters solution Given grams – convert to moles Can find any of these terms as long as have 2 Dilutions = using a standard solution to make a new solution M 1 V 1 = M 2 V 2 1 = before dilution (standard/stock solution) 2 = after dilution (new solution)

Describing solutions Tell how the solution would be made by writing out a sentence. – Dissolve X grams of solute in enough solvent to get Y liters of __ M solution – Dilute X liters of stock solution in enough water to make a ____ M soltuion

Precipitation Reaction Using solubility rules determine what is soluble and insoluble in the equation Soluble compounds will dissolve and break up into their ions – Label with (aq) Insoluble compounds will not break up (gases and liquids also insoluble) – Label (s) Take formula equation and break up compounds to get complete ionic equation cancel out whatever is the same on both sides of the equation (called spectator ions) Rewrite what is left = called net ionic equation ( should only be what makes up the solid, gas, or liquid)

Acid-Base Reaction Also called neutralization reaction – Acid(aq) + Base(aq)  salt + water(l) Acid-base titrations are used to determine the exact volume or concentration needed – Titration – using a buret to deliver substance of known concentration (titrant) into a solution of unknown concentration (analyte) Volumetric analysis – technique to determine amount of a substance by doing titration – Use an indicator to show when nearing the equivalence point – color begins to appear but goes away – Endpoint is when the equivalence point has been reached – completely changes color

Oxidation-Reduction Reaction Called Redox for short Species in the reaction will transfer electrons Must identify the oxidation states (oxidation numbers) for all species involved – Like imaginary charges (most match regular charges) – Sum of molecule must equal zero – Sum for Polyatomic ions must equal their charge – Element represented by itself gets value of 0 Identify which is being oxidized and which is being reduced – OIL RIG – Oxidation involves loss (oxidation state increases) Called reducing agent – Reduction involves gain (oxidation state decreases) Called oxidizing agent

Balancing Redox Balancing using oxidation states Show electrons gained/lost by drawing lines (ties) Use coefficients to equalize electrons gained/lost Balance the rest by inspection and add states Balancing using the half reaction method Write half reactions – break up equation – Oxidation half reaction – Reduction half reaction Balance each by adding electrons to have charges balance Balance in acid or base – pay attention to specifics for each. – Acid adds H+ while base adds H 2 O