Week 2/3 notes. Chapter 3.3- 3.8
Week 2/3 notes. Chapter 3.3- 3.8 CHEM 103
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This 7 page Class Notes was uploaded by alex burgy on Saturday September 19, 2015. The Class Notes belongs to CHEM 103 at University of Wisconsin - Madison taught by Martin Zanni in Fall 2015. Since its upload, it has received 104 views. For similar materials see Chemistry 103- General Chemistry in Chemistry at University of Wisconsin - Madison.
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Date Created: 09/19/15
33 Precinitation Rethions Dissociation is the process by which cations and anions separate when an ionic compound dissolves Ex NaClaq Naaq Cl39aq Electrolytes substances that conduct an electric current when dissolved in water 0 Strong electrolyte is a compound that completely dissociates into its ions when it forms an aqueous solution 0 Weak electrolyte is a compound that dissociates only partially when it forms an aqueous solution Solubility rules look to table 31 on page 101 for these Do not have to memorize If a compound contains at least one for the ions indicated for soluble compounds in table 31 then the compound is at least moderately soluble Precipitation reaction is a reaction in which one or more insoluble products form from soluble reactants Ex PbN032aq Pb2aq 2 NO3aq K2Cr04aq 2 Kaq CrO4239aq PbN032aq K2Cr04aq 2KN03aq PbCrO4s Spectator ion any ion that is presented but is not involved directly in the reaction 34 AcidBase Re ons Acids Acids any substance that increases the concentration of aqueous Hydrogen ions Haq when dissolved in pure water The properties acidic solutions have in common are the properties of Haq Ionization is a process in which a molecule is transformed into positive and negative ions One of the ions formed by an acid is always Haq Strong acid An acid that is entirely converted to ions completely ionized when dissolved in water is a strong electrolyte aka a strong acid Weak acid an acid that ionizes only slightly is a weak electrolyte and is called a weak acid Bases Base is a substance that increases the concentration of aqueous Hydroxide ions OH39 aq when dissolved in pure water The properties that basic solutions have in common are properties attributed to the aqueous Hydroxide ion OH39 aq Strong base a soluble ionic compound that contains Hydroxide ions ex NaOH s H20 Na aq OH39 aq Weak base a weak electrolyte that produced OH39 aq ions Neutralization Reaction Acidbase neutralization reaction an acid reacts w a base and each neutralizes the properties of the other ex HCl Hydrochloric acid H aq Cl39 aq ex NaOH sodium Hydroxide Na aq OH39 aq HClaq NaOH aq H20 1 NaCl aq Net Ionic Equations for AcidB ase Reactions Reactions in Which Gases are Formed Gas forming reaction a reaction in which a gas is generated ex CaC03s HCl aq CaClz aq H20 1 C02 aq 0 Carbon dioxide always forms when acid reacts w metal carbonates 35 OxidationReduction amp Electron Transfer OxidationReduction Reaction one in which e39 are transferred from one reactant atom molecule or ion to another Oxidation is a loss of e39 from an atom molecule or ion After the loss of e39 the atom molecule or ion has been oxidized Reduction is a gain of e39 by an atom molecule or ion After the gain of e39 the atom molecule or ion has been reduced 2 Fundamental Conclusions 1 In every redox reaction the transfer of e39 occurs simultaneously E39 are lost by one reactant while being gained by another reactant When one reactant is oxidized another reactant must be reduced 2 Oxidation e39 loss is opposite of reduction e39 gain Oxidizing agent is a substance that causes something else to be oxidized Reducing agent is a substance that causes something to be reduced 0 The oxidizing agent is reduced by taking e39 from the reducing agent In this way the oxidizing agent causes the oxidation e39 loss of the reducing agent 0 The reducing agent is oxidized by donating e39 to the oxidizing agent By doing so the reducing agent causes the reduction e39 gain of the oxidizing agent 0 As a result oxidizing agents reduce reducing agents are oxidized Ex Formation of Magnesium Oxide Mg metal atoms are oxidized lose e39 so Mg is the reducing agent oxygen atoms are reduced gain e39 making oxygen the oxidizing agent Mg metal the reducing agent causes oxygen to reduce oxygen the oxidizing agent causes the Mg metal atoms to be oxidized Most metals are reducing agents and those in Groups 1A amp 2A are strong reducing agents A few nonmetallic elements such as oxygen and the halogens are strong oxidizing agents Remembering Trick Remember 3 words Ox Red Agent If the Substance is oxidized it is the Red Agent You only used each word one time or If the substance is Reduced it is the Ox Agent You only used each word one t1me Oxidation amp reduction occur readily when a strong oxidizing agent come into contact w a strong reducing agent The Oxidation oxidation state of an atom in a chemical formula is a measure of the apparent positive charge in the atom 0 Rule 1 The oxidation of an atom of an element is 0 ex Fe in metallic iron or C1 in C12 each has an ox of 0 0 Rule 2 The oxidation number of a monatomic ion equals its charge thus the oxidation of Cu2 is 2 and that of 8239 is 2 0 Rule 3 The sum of the oxidation numbers over all atoms in a complete formula for a compound is 0 0 Ex in H20 two times the Ox of each of the two H atoms plus the one times the Ox of one O atom must equal 0 0 Rule 4 The sum of Ox s over all atoms in a polyatomic ion equals the charge on the ion 0 Ex in NOz39 ion one times the Ox of N plus two times the Ox of O must equal 1 corresponding to the 1 charge on it 0 Rule 5 In an ionic compound Ox s in the cation are independent of those in the anion 0 Ex In NH4NOz separate OX s are assigned for the N in NH4 and the N in NOz39 0 Rule 6 Atoms of some elements have the same Ox in almost all of the compounds 0 An atom of F1 always has and OX of 1 o Atoms of the Alkali metals Li Na K Rb Cs have an Ox of 1 in nearly all their compounds 0 Atoms of the Alkalineth metals Be Mg Ca Sr Sc have an Ox of 2 in nearly all of their compounds 0 Hydrogen has an Ox of 1 unless it is combined w a metal in which case its oxidation is 1 0 Rule 7 Apply rules 7a amp 7b only of rules 16 have not determined Ox s for all atoms in a formula 0 a Oxygen has an Ox of 2 unless Rules 16 have already given Oxygen a different Ox o b In binary compounds of nonmetals the element closer to F1 in the periodic table is given a negative Ox equal to the charge on its common monatomic ion Because oxidation s indicate transfer of e39 oxidation always change during redox reactions Oxidation is defined as an increase in oxidation number from reactant to product the becomes more positive 0 Reduction is defined as a reduction in oxidation number from reactant to product the becomes less positive more negative Disproportionation reaction is a rare case when a reactant can serve as both the oxidizing and the reducing agent Ex C12g HzOl Haq Cl39aq HOCl aq pg 120 Activity series of metals table 34 ranks metals in order of decreasing ability to donate e39 during redox reactions A metal higher in the series will reduce ions of any metal lower in the series 36 The Mole Mole ration is a proportionality factor that relates the amount of one substance in the equation to the amount of another 3i Limiting reactant is that is completely converted to products 0 the amounts of products fromer is are always determined limited by the initial amount of limiting reactant 38 Percent Yield Theoretical yield the maximum quantity of product is called this Actual yield the quantity of desired product actually obtained from a synthesis Percent yield the ratio of actual to theoretical yield Percent yield Actual theoretical X 100 Green clean is the design development and the implementation of chemical products and processes to reduce or eliminate the use and generation of substances hazardous to human health and enVironment Atomic economy the fraction of the mass of starting materials that ends up in the desired final product or products 39 Combustion Analysis Combustion analysis a known small mass of compound especially organic compounds of C and H is burned in excess 02 converting all the C in the compound to C02 and all Hydrogen to H20 EX 1200g of butyric acid was burned 241 g of C02 and 982g H20 were produced 0 Calculate in grams of C H O mC in sample 241g of C02 X 1 mol C024401g C02 X 1 Mol C 1 Mol C02 X 1201g of C 1 Mol C 658g ofC mH in sample 982g of H20 X q Mol H20 1802 H20 X 2 Mol H 1 Mol H20 X 10079g H 1 Mol of H 110g ofH mO in sample 1200g 685g 110g 432g 0 0 Calculate the amount of each element in the sample NC in sample 658g of C X 1 Mol of C 1201 g C 0568 mole of C NH in sample 110g of H X 1 Mol of H 10079g H 109 mol of H NO in sample 432g of O X 1 M01 0 1600g of O 027 M01 of O 0 Obtain ratios 0548 Mol of C 0270 Mol of O 203 M01 of C 100 M01 of 0 amp 109 M01 of H 0270 Mol of O 403 mol of H 100 M01 of 0 You get 1 oxygen to 2 carbons to 4 hydrogens 1 O 2 C 4 H 310 Solution Concentration MolaritV Solute a substance that has been dissolved Solvent the thing that does the dissolving Concentration or Molarity the amount of solute per unit volume of solution Molarity amount of solute moles volume of solution liters 0 Calculate molarity 433 g of KMnO4 in 5000mL of water Molar mass of KMnO4 is 15803 gmol nKMnO4 433 g KMnO4 X 1 mol KMnO4 15803 KMnO4 274X 10393 mol KMIIO4 Molarity of KMnO4 cKMnO4 274X10393 mol KMnO4 5000 mL X 1000MmL 1 L 548X10393 MolL Dilution adding solvent to make a solution of lower concentration The amount of solute in the diluted solution is exactly the same as it was the concentrated solution cconc X vconc amount of solute cdil X vdil EX HCl solution diluting 250 mL of 60 M01 HCl to 500 mL Cdil Cconc X vconc vdil 60 MolL X 0250 L 500L 30 M01 L 312 Titrations in Aqueous Solutions Titration one Solution is added to another solution until just enough of the first solution has been added to react with all of the second solution Equivalent point the point at which the amount of reactant in the solution has been added just enough to react completely with the reactant in the other solution Standard solution a solution whose concentration is known accurately Indicator is a substance that can be added in a titration to show when the equivalent point has been reached End point the point at which an indicator is seen to change color Text Used Chemistry The Molecular Science 5th Edition with OwlV2 Online Homework Authors Moore and Stanitski Publisher Cengage
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