Chem 107, ch 4
Chem 107, ch 4 Chem 107
University of Louisiana at Lafayette
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This 3 page Class Notes was uploaded by Alexandra Notetaker on Wednesday October 5, 2016. The Class Notes belongs to Chem 107 at University of Louisiana at Lafayette taught by Dr. Daniel Rivera in Fall 2016. Since its upload, it has received 2 views. For similar materials see General Chemistry I in Chemistry at University of Louisiana at Lafayette.
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Date Created: 10/05/16
Chemistry notes on Reactions in Aqueous solutions Homogenous mixtures are called solutions (when the particles mix well) o Part that changes state is called solute o Part that dissolves a solute is called solvent o Dilute solutions: relatively small amount of solutes o Concentrated: relatively large amount of solutes Solution concentration is measured by molarity o Amount of solute in moles divided by volume of solution in liters o To dilute a solution you mix a new solution is made from a stock solution CV=CV Concentration of a solution depends on the amount of dissolved solutes per amount of solvent If two substance are capable of mixing the are called miscible; if the are immiscible the cannot mix Solubility describes the amount of one substance that will dissolve completely in a specified amount of solvent o Temperature affects solubility. Generally it increases solubility o Pressure affects only the solubility of gases o A saturated solution contains and equal amount of dissolved solute and undissolved solute o Unsaturated solutions contain less solute per volume than its saturated solution o Supersaturated solutions contain more solute per volume than its saturated solution Solution stoichometry can be used to figure out volumes or moles of unknown solutions o General formula for calculations is volume A > moles A> moles B> volume B When compounds are made of similar components they will dissolve completely (likes dissolve likes) When mixed together there are attractive forces between solvent and solutes called solute-solvent interactions o This is seen especially in strong electrolytes that completely dissociate into ions where dissolved in a solution. The dissociated ions will be surrounded by the particles in a solvent and form weak bonds Especially when the solvent is water, partial charge distributions can cause certain molecules or elements to be attracted to one another within the mixture Electrolytes: for a solution that will conduct electricity when dissolved o Strong > completely dissociate into ions when dissolved o These are: Ionic substances Strong acids and bases o Weak> only partially dissolve and some will remain as intact compounds o These are weak acids and bases Nonelectrolytes: will not conduct electricity when dissolved o These are mostly covalent compounds A compound is termed soluble if it dissolves in water and insolvable if it doesn't Precipitation reactions occur when a solid forms when two solutions are mixed o The solid is called a precipitate o Left over substances that didn't form the precipitate are called spectator ions o A net ionic equation is a written precipitation reaction without the spectator ions Arrhenius definition of acids and bases o Acids form H+ ions when dissolved in water Polyprotic acids contain more than one ionizable proton and release them sequentially o Bases form OH- when dissolved in water Naming acids o Binary acids: have H+ cation and nonmetal anion Write nonmetal name Has hydro prefix, write ic as the ending and write the word acid after o Oxyacids: have H+ cation and polyatomic anion Write polyatomic ion and depending on the ions ending change ending to ic if the poly ends in ate or change to ous if it ends in ite add the word acid to the end Note: for Oxyacids we don't add hydro as a prefix An acid base reaction is called a neutralization reaction o This particular reaction is completed when the moles of acid equal the moles of the base in the solution The product of a neutralization reaction is water and a salt Titration- a substance in a solution of a known concentration is reacted with another substance in a solution of an unknown concentration o The endpoint is when the reactants are in their stoichiometric ratio o This is usually done in an instrument called a burette o To be able to tell when the endpoint is reached, a chemical called an indicator is added that will change colors bases upon the changed of acidity/ alkalinity o When H+ equal OH- it's called the equivalence point Gas- evolution reactions occur when two solutions are mixed together and a gas forms as a product o The concept is the same as the precipitation reaction Oxidation- reduction reactions o Also called redox reactions o Atoms that lose electrons are being oxidized These are also called reducing agents o Atoms that gain electrons are being reduced Also called oxidizing agents o Oxidation numbers are assigned to elements participating in chemical reactions so that we can see whether or not a redox reaction has occurred o There are a set of rules that are used to assign these numbers Free elements and the sum of compounds equals zero Monoatomic ions and the sum of polyatomic ions equals their charge Group 1 metals have oxidation number +1 Group two metals have oxidation number +2 Fluorine -1, hydrogen +1, oxygen -2, group 7 -1, group 6 -2, group 5 -3 o Note: the higher up in this list of rules the more priority that particular element has o From there we can set up mini math problems to figure out complimentary oxidation numbers o After all numbers have been assigned, we can see whether or not elements underwent a change in their oxidation numbers during the chemical reaction Gravimetric analysis o Used to find percentages of unknown substances in certain solutions using its chemical reaction equation
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