Chemistry and the Environment: Chapter 4-5 Study Guide
Chemistry and the Environment: Chapter 4-5 Study Guide CHEM 105
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This 6 page Study Guide was uploaded by Haley Deml on Thursday October 8, 2015. The Study Guide belongs to CHEM 105 at St. Cloud State University taught by Dr. Roby Kurian in Fall 2015. Since its upload, it has received 105 views. For similar materials see Chemistry and the Environment in Chemistry at St. Cloud State University.
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Date Created: 10/08/15
Chemistry and the Environment Study Guide 2 Chapter 4 5 Chapter Four Molecules Compounds and Chemical Reactions 0 O O v Molecular Changes Cause behavior of matter No exception to rule 339 Chemical Compounds 0 O 0 Two elements that are bonded together H20 2 Hydrogen atoms bonded to 1 Oxygen atom 339 Chemical Formulas O O 0 Indicates the elements present in the compound as well as the number of atoms of each element ie H20 I 2 Hydrogen to every 1 Oxygen If you change any numbers in the formula you will change the chemical makeup itself Joke Two chemists go into a restaurant The first one says quotI think I39ll have an H20quot The second one says quotI think I39ll have an H2O tooquot and he died C6H1206 Glucose Formula I 6 Carbon Atoms I 12 Hydrogen Atoms I 6 Oxygen Atoms v IonicMolecular Compounds Electron configurations EC shows which elements have stable orbitals Noble Gases have a stable outer orbital that contains 8 electrons Elements with unstable EC will form compounds and transfer electrons or sharing electrons to other elements to gain stability 0 O O v Ionic Compounds Metal and Nonmetal compound ie NaCl Sodium Chloride Metals Na lose electrons while Nonmetals Cl39 gain electrons Subscripts represent the ratio of atoms in a compound 339 Molecular Compounds 0 O 0 Contain only Nonmetals Electrons are shared but not evenly ie H20 This is a covalent bond Subscripts represent the actual s of each kind of atom in the molecule I 2 hydrogen molecules for every 1 oxygen molecule Naming Compounds 0 Ionic Compounds I Name begins with cation metal I Followed by the base name of the anion nonmetal ide I NaBr sodium bromide I MgBr2 Magnesium Bromide I Don t contain prefixes to show the of each type of atom 339 Common Anions 0 000000 FluorineFluoride ChlorineChloride BromineBromide Iodine Iodide OxygenOxide Sulfur Sulfide Nitrogen Nitride Chemistry and the Environment 0 v Example 0 L120 I Lithium Oxide 339 Naming Compounds Continued 0 Anions and Polyatomic Ions I Polyatomic Ions Names Formula Acetate CH3COO39 Ammonium NH4 Carbonate C032quot Chlorate C103quot Chromate CrO4239 Cyanide CN39 Dichromate Cr202239 Dihydro gen H2PO439 Phosphate Hydrogen HCO339 Carbonate Hydrogen HPO4239 Phosphate Hydrogen HSO439 Sulfate Hydroxide OH39 Hypochlorite ClO39 Nitrate N03quot Permanganate MnO439 Phosphate PO43quot Sulfate SO4239 Su1fite SO3239 Nitrite N02quot I Polyatomic ions are made up of two or more atoms and behave as a single unit I Ex MgOH2 Magnesium Hydroxide 0 Molecular Compounds I The metallic element is listed first followed by nonmetallic element I ie CaCO3 I Calcium Carbonate Study Guide 2 O 09 O 09 Chapter 4 5 I Prefixes are used to show the of atoms of the element that are present I Mono prefix is not used on the first element I Ex N205 dinitrogen pentoxide Prefixes Pre x 1 Mono 2 Di 3 Tri 4 Tetra 5 Penta 6 Hexa 7 Hepta 8 Octa 9 Nona 10 Deca Formula Mass Formula Mass Weight Atoms x Atomic Weight 0 EX Nazs o Na 2 atoms x 2299 4598amu 0 81 atom x 3206 3206amu o 4598 3206 7804amu 0 Formula Mass 7804amu Molar Mass MM o It is the same as Formula Mass it just has different units 0 Conversion Factor between grams and moles of a compound Moles to Grams Grams to Moles Formula MM of sub Grams of substance in rams Moles of substance 1 mole Ex 100 grams sample of H2S 0 Molecular Mass H2 2016mm S 32060mm 34076mm o How many moles Step 1 Chemistry and the Environment 100g H28 34076mmH28 X moles 1 mole 339 Step 2 Cross Multiply 100g H28 X 1 mol 34076mm X xmoles 339 Divide 100g H28 34076 0293 moles 0 To find grams you would leave g of substance empty and fill in how many moles there are 339 If you need to go from grams to molecules atoms you will use this diagram to help you Grams of Substance Divide Multiplytl by by Molar Molar Mass Mass V Moles of Substance Divide n Multiply by by Avogadr Avogadr o s o s V Number of Atoms or Molecules 339 EX 100 g sample of H28 Study Guide 2 Chapter 4 5 o How many molecules 339 Step 1 100g H28 X 1 mol H28 029346 mol 34076g H28 339 Step 2 029346 melH28 X 6022X1023molecules 1 mol 339 Step 3 Answer 177X1023 molecules 0 You can do it all in one as well and you ll get the same results 0 100 x 60221023 34076 339 Chemical Formulas as Conversion Factors 0 Chemical formula gives equivalences between the elements in a particular compound 0 2 Hydrogen atoms H2O molecule 339 EX 525g of H28 0 How many moles of H are present 0 We know that H28 has 34076 g already 5 252 H28 1 mol H28 2mol H atoms l34076g st 1 mol st 0308 moles of H 339 Chemical Reactions 0 Chemical reactions result in compounds 0 Compounds can be transformed by further chemical reactions called chemical equations CH4 202 V CO2 2H2 Reactants Products 0 The equation must be balanced and each element must have the same on both side of the equation Chemistry and the Environment 0 v Balancing Equations 0 Rules Change only coefficients not subscripts o If an element stands alone 02 balance that last 0 If an element occurs in only one compound balance first CH4 02 gt C02 H20 C l C 1 H 4 H 2 O 2 O 3 UNBALANCED 339 Step 1 start with carbon or hydrogen 0 Carbon is already equal on both sides so we move on to Hydrogen CH4 02 gt C02 2H20 C l C 1 H 4 H 2 4 O 2 033 4 339 Step 2 Balance Oxygen CH4 202 V C02 2H20 339 C l C 1 339 H 4 H 24 339 O 2 4 O 3 4 BALANCED 339 Stoichiometry N2 3H2 gt 2NH3 o How many moles of nitrogen gas are required to convert 115 moles of Hydrogen gas to ammonia 115 molesH2 I 1 mole N2 I 3 moles H2 I 383 moles of N2 CH4 202 gt C02 2H20 339 Using this balance equation we will find out how many grams of H20 are produced when 213X108 grams of methane is burned per day v Make sure to find the molar mass of both CH4 and H20 to help with the conversion 213X1082CH4I 1molCH4 I2 molH2O I 1802gH2O 1604gCH4I lmolCH4 lmolH2O Study Guide 2 Chapter 4 5 479 X108g H2O Chapter Five Chemical Bonding 339 Lewis Theory 0 A model for chemical bonding 339 Valence Shell Electron Pair Repulsion VSEPR o A theory that allows the prediction of the shapes of molecules based on the idea that electrons either as one pairs or as bonding pairs repel one another 0 EX It predicts H2O to have a bent or boomerang shape 339 GN Lewis s model focuses l Valence electrons are most important in chemical bonding 2 Valence electrons are transferred from one atom to another to form ionic bonds or shared to for covalent bonds 3 Being transferred or shared causes a fain in stability in electron configurations because of the octet rule a Meaning they will have 8 electrons around their outer orbital making them stable 339 Lewis Structure 0 element symbol surrounded by of dots that the of valence electrons I ignore inner electrons I doesn t matter where you put the dots 0 ex Si39 Chemistry and the Environment 0 Chemical bonding brings elements together so they can become stable 0 Stablility is a result of atoms forming an octet 391 Ionic Lewis Structure 0 The transfer of electrons from a metal to a nonmetal 0 Metal becomes a cation I A positively charged ion I Loses electrons o Nonmetal become an anion I Gained electrons I Are negatively charged EX N 39Cl gt NaC1l39 U 0 O O 391 Charges Ionic Lewis Structures 0 Charges go to the upper right corner of the symbol I Na 0 Put the anion in brackets 39 Cll39 9 v Covalent Lewis Structures 0 Covalent bonds share electrons 0 Both atoms have eight electrons I The atoms just share one of the bonds I That is called bonding pairs 0 Electrons on a single atom that do not share a bond are called lone pairs 0 Bonding pair electrons count toward the octet of both atoms EX H I O O H O H o 0 Study Guide 2 Chapter 4 5 0 Line represents the bonding pairs 0 Two individual dots represents lone pairs 391 Multiple Bonds 0 Elements can create double bonds or triple bonds to complete the octet EX Ioof 9 v Draw the structure of CH4 1 H C H H 9 v Chemical Bonding in Ozone o Atmospheric gas that protects life on Earth from excessive UV light 393 Lewis Structure Ozone o 2 valid structures 0 o 00 00 00 O OOlt gtO O O quot g o co quot 391 These are resonance structures 0 Represented with double arrow between them 391 The shape of Molecules o Helps determine properties of substances 0 VSEPR allows us to predict molecule shapes from their Lewis Structure eX N Hy WH H Ends up looking like a pyramid with a triangle bottom Chemistry and the Environment Study Guide 2 9 v Best to Look at table 5 1 in your book 391 Electronegativity 0 Increase as you move right across a row on the periodic table 0 Decreases when you go down a column 0 Polar bond I Uneven electron distribution I A negative and positive pole o Entire molecule may be polar I Uneven electron distribution with the molecule I A negative pole and positive pole 391 Bond Polarity A O K Positive end Negative end 391 Electronegativity is a measure of an atom s ability to attract electrons in a bond 0 CO is a polar molecule 0 C02 has polar bonds but is nonpolar 0 Because the two Oxygen are pulling away from each other the polar bonds cancel out 391 If you look at the structure CF4 0 We can tell C F is a polar bond 0 But with all 4 Fluorine atoms pulling away from each other Chapter 4 5 it is overall a nonpolar molecule
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