Test 3 Study Guide
Test 3 Study Guide CH 101
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This 16 page Study Guide was uploaded by Rani Vance on Tuesday October 20, 2015. The Study Guide belongs to CH 101 at University of Alabama - Tuscaloosa taught by a professor in Fall 2015. Since its upload, it has received 62 views. For similar materials see General Chemistry in Chemistry at University of Alabama - Tuscaloosa.
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Date Created: 10/20/15
Chem 101 Study Guide I will include all my notes for this test Additionally I will include my work for some of the homework problems Most of the problems for empirical formula just require lots of practice to really understand them I would make sure to understand all of the learning objectives as well Learning Objectives Lewis Structures Classify a compound as ionic metallic or covalent compounds are neutral Ionic compounds attraction between cations and anions electron is transferred Metallic compounds Covalent occur between two nonmetals electron is shared 0 Draw Lewis dot diagrams of atoms Practice practice practice the symbol of the electron represents the inner nucleus valence electrons are represented by the dots that surround the symbol Predict ionic formula from Lewis diagrams For example if a dot diagram contained Mg with 2 single electrons and O with 2 single electrons and two pairs of electrons the ionic formula would be MgO because both elements have 2 unpaired electrons that can be shared to create a full octet we can predict this because a metal atom should lose electrons and a nonmetal should gain electrons Explain experimental properties of ionic compounds using Lewis Bonding Theory we can predict the relative strengths of resulting ionic bonds from Coulomb s law Lewis Diagrams for covalent compounds Articulate the difference between covalent bonding and ionic bonding Because nonmetal atoms have relatively high ionization energies it is difficult to remove electrons from them They must share electrons in order to create a full octet Construct Lewis diagrams for covalent molecules Practice practice practice can form single double and triple bonds the more bonds there are the shorter the bond should be The more electrons two atoms share the stronger the bond Explain property differences ionic and covalent compounds Covalent attractions between atoms are directional melting and boiling point for covalent compounds is relatively low should not conduct electricity because there are no charged particles around that surround them Ionic transfer of an electron from a metal to a nonmetal tend to form crystals in solid state held together by electrostatic interactions high melting and boiling points Naming Ionic Compounds Know how to name ionic compounds including 1 write the symbol for the metal cation and its charge 2 write the symbol for the nonmetal cation and its charge 3 charge without sign becomes subscript for other ion 4 reduce to smallest whole number ratio 0 polyatomic ions eg oxy anions Binary compounds that contain a metal and form a cation follow the formula Ex NaCl Cation keeps name of element name of anion ide suffix sodium chloride Polyatomic Ions ate9 chlorate ate ions 1 0 9 same charge per prefix ate ion 1 0 9 same charge ite suffix ate ion 2 0 9 same charge hypo prefix ite suffix o Metals with multiple possible charges Metals that can form two types of cations Chromium Cr2 Chromium II Cr3 Chromium III Iron Fe2 Iron II Ferrous Fe3 Iron III Ferric Tin Sn2 Tin II stannous Sn4 Tin IV stanic Copper Cu1 Copper I cuprous Cu2 Copper II cupric hydrates Hydrated Ionic Compounds many ionic compounds form hydrates Naming Molecular Compounds prefiX name of 1st element prefix base name of second element ide Molar Mass Apply the concept of the mole to molecules 6022 X1023 0 Calculate the molar mass of compounds of atoms of 1St element atomic mass of the 1st element of atoms of 2rld element atomic mass of the 2rld element 0 Calculate element percent composition Mass of 1 element X 100 Mass of molecule 0 Calculate an empirical formula from experimental data Calculating the Empirical formula 1 Convert the to grams assume you start with 100g of the compound 2 Convert g9 moles 3 write pseudoformula using mol transcripts 4 divide all by smallest of moles if result is Within 01 round to the nearest Whole 5 Multiply all mol ratios by to make Whole a if ratio is 5 X by 2 if 33 or 67 X by 3 if 2575 X by 4 Week of Notes 105109 Stable Electron Arrangements and Ion Charges Metals form cations 10st electrons to get the same electron configuration as the previous noble gas nonmeta1s form anions by gaining electrons to get the same electron configuration as the next noble gas EX Octet Rule when atoms bond they tend to gain lose or share electrons to result in eight valence electrons n2 np6 Exceptions He Li Be B attain an electron configuration like He Lewis Symbols can be used to represent the transfer of electrons from metal atom to nonmetal atoms resulting in ions that are attracted to each other and therefore bond Lewis Theory predicts the number of electrons a metal atom should lose or a nonmetal atom should gain in order to attain a stable electron arrangement octet rule Predicting Ionic Formulas electrons transferred when metal loses all its valence electrons electron and the nonmetal has an octet Ionic Bonding in solid state ionic compounds tend to form crystals held together by electrostatic interactions breaking down crystal Ionic Compounds to conduct electricity a material must have charged particles that are able to ow through the material ionic compounds dissolve in water solution conducts Chapter 5 Lewis Diagrams for Covalent Compounds nonmetals have relatively high ionization energy so it is difficult to remove electrons from them nonmetals bond together by sharing electrons sharing holds atoms together potential energy lowest between two atoms Clicker Question How many valence electrons do main group elements want to obtain Answer 8 valence electrons Lewis Theory of Covalent Bonding atoms can achieve octet of valence electrons by sharing their valence electrons with one another sharecovalent bonding AG a LS qr u 3911 law xigr ll wfquot W434i 5 My M y 1rx4r c 4 J pgri r m MWMS mm Xgu on ctatti 1 HF rm 1 Ff H 5 fW mm lemma WWW m born pm W 55quot 1 a 5 M2911 MM1mqu azmmr JWP WY 0W 3 L3 Joe 0 X oz wmm pm H 3 vquot 39 390 303 Lewis think valence electrons Diagrams of Covalent Bonding When two atoms share 1 pair of electrons it is called a single covalent in a double covalent bond two atoms share two pairs of electrons share 4 electrons in double covalent triple covalent three atoms share two pairs of electrons share 6 electrons in triple covalent atoms do not always have the same number of lone pair electrons they had before bonding Covalent bonding the more electrons two atoms share the shorter the bond should be 9higher bond ordershorter bond Lewis Theory Predicts that the more electrons two atoms share the stronger the bond should be triple bonds require lots of energy to break them double bonds require a medium amount of energy to break them single bonds require less energy to break thme Lewis theory implies that some combinations should be stable whereas others should not because stable combinations result in octets or duets Lewis theory of covalent bonding implies that the attractions between atoms are directional interactions between bonding is strong but interactions between molecules is weaker Predicts melting and boiling points Melting point generally lt 300 degrees C molecular compounds are found in all 3 states at room temperature Covalent bonding neither molecular solids nor liquids conduct electricity no charged particles around all material to conduct 109 Naming Ionic Compounds How to Name Ionic Compounds remember ionic compounds form as a result of the attraction between cations and anions compounds are neutral Write formula of a compound 5 write the symbol for the metal cation and its charge 6 write the symbol for the nonmetal cation and its charge 7 charge without sign becomes subscript for other ion 8 reduce to smallest whole number ratio Naming ionic compounds binary ionic compounds containing a metla that forms one type of cation are simple to name NaC19 cation is same as element name of anion ide suffix sodium chloride Metals that can form two types of cations Chromium Cr2 Chromium II Cr3 Chromium III Iron Fe2 Iron 11 Ferrous Fe3 Iron III Ferric Tin Sn2 Tin II stannous Sn4 Tin IV stanic Copper Cu1 Copper 1 cuprous Cu2 Copper 11 cupric Patterns of Polyatomic Ions 1 Elements in same column form similar polyatomic ions 2 if polyatomic ions start with W H add hydrogen Naming Ionic Compounds Na2 SO4 1 Identify the ions 2 name the cation sodium 3 name the anion sulfate 4 sodium sulfate Polyatomic Ions ate9 chlorate ate ions 1 0 9 same charge per prefix ate ion 1 0 9 same charge ite suffix ate ion 2 0 9 same charge hypo prefix ite suffix Hydrated Ionic Compounds many ionic compounds form hydrates Naming Molecular Compounds prefix name of 1st element prefix base name of second element ide Chem 101 Week of Notes 10121016 10 12 Molar mass of compounds contribution chemical formula What is a mole 6022x 1023 Molar mass of a compound is equal to the sums of atomic masses of its constituent elements Formula mass of atoms of 1st element atomic mass 1st element of atoms of 2rld element atomic mass of 2nd element Example NaCl formula MMNa MMCI 2299 gmol Na 3545 gmol Cl 5844 gmol Water 11008 gmol H 2 1600 gmol O 18016 gmol 9 1802 gmol Mass of moles X molar mass What is the mass of 25 moles of NaCl Nmol Nac1 25 mol MMNaC1 5844gmol 25mol NaCl 5844 gmol NaCl 1461 g Clicllter Question Find the molar mass of CH4 Answer 1201 gmol C X 1 gmol H4 1601 g How many formula units of NaCl are there in 1 mol 6022 X1023 How many formula units are there in 8766 g of NaCl Mass moles of molecules 5844 gmol of NaCl 8766 g 1 mol X 6022 X 1023 molecules 903 X1023 molecules 5844 gmol 1 mol How many atoms of 02 are present in 32 g of water Mass of water 32g MM of water 18g Mass of water moles of water moles 02 32g X 1 mol 1778 mol 18g mol How many moles in 453 of A12 SO43 A12 227 gmol 54 S 33206 gmol 96 O 121600 gmol 192 342 453g lmol 0132mols 342 gmol Chemical formula Empirical formula gives the relative of atoms think of it as a ratio Molecular gives the actual of atoms ex A12 SO43 EX Molecular Empirical Glucose C6H1206 CHzO Hydrogen Peroxide H202 HO Carbon Dioxide C02 C02 Water H20 H20 Composition Chemical formulas give the element ratio Within a compound EX C6H1206 Ratio 1 C 2 H 1 0 Mass ratio different from atom ratio How to calculate composition mass of 1 element mass of element in moles Mass of molecule mass of 1 mole of molecule Find the C by mass in C02 Mass of C mass C in moles CO Mass of C02 in mole C02 MM C02 MMC 2 MMO 1201gmol 21601gmol 4401 gmol 9 1201gmol 273 4401 gmol How do chemists know What the composition of something is Chemists are able to very precisely measure the gases generated When something is combusted Works well Wcompounds containing H amp C What comes out C02 H20 Chapter 5 Calculating the Empirical formula 6 Convert the to grams assume you start With 100g of the compound 7 Convert g9 moles 8 write pseudoformula using mol transcripts 9 divide all by smallest of moles if result is Within 01 round to the nearest Whole 10 Multiply all mol ratios by to make Whole a if ratio is 5 X by 2 if 33 or 67 X by 3 if 2575 X by 4 MUST KNOW HOW TO DO FOR EXAM Composition9 Empirical Formula EX 1 C 4000 H 671 O 5328 1 C9 4000g H9 671g 09 5328 g 2 g9 moles C 4000g X liol 333 moles C 1201g H 671g X 1 mol 664 moles H 101g O 5328g X 1mol 333 moles O 1600g 3 C333 H664 0333 4 Divide by the smallest 333 9 C1 H199 01 9 round if it is Within 01 C1 H2 01 5 this step is not necessary for this example because they are easily rounded to Whole numbers EX 2 1 C 6000 9 6000 g C H 448 9 448 g H O 3553 9 3553 g 0 2 C 60g X 1mol 4996 moles l20lg H 448 g X 1 mol 443 moles l01g O 3553g X 1 mol 2221 moles 1601g 3 C4996 H443 02221 4 smallest number C2249 H1997 01 5 multiply to make a Whole ratio multiply by 4 because 025 9 C9 H8 04 empirical formula Chapter 6 Polar Covalent Bonding Covalent bonding between unlike atoms results in unequal sharing of the electrons one atom may pull an electron in the bond closer to itself bond becomes polar shifts to one side Result is a polar covalent bond atom With larger bond electron density gets a partial negative charge atom With less bond electron density gets a partial positive charge Electronegativity the ability of an atom to attract bonding electrons to itself is called electronegativity Most EN element is F least EN element is Fr the larger the difference in EN the more polar the bond F is good at attracting electrons because of the effective nuclear charge F more EN than H9 bond shifted toward F H9 partial positive 9 dipole partial and partial Bond Polarity most bonds have some degree of sharing and some degree of ion formation to them bonds classified as covalent if the amount of energy transfer in insufficient for the material to display the classic properties of ionic compounds if sharing is unequal enough to produce dipole Know polar ionic spectrum Determine What bond NO ENN 30 ENC 35 ENdelta ENCENN 05 biggestsmallest 05 on scale polar covalent Bond Polarity ClCl pure covalent HCl 3021 09 polar covalent Bond Dipole Moments Dipole moment mu is a measure of bond polarity material With positive and negative end directly proportional to size and charges Generally the more electrons two atoms share and the larger the atoms are the larger the dipole moment 1016 Exceptions to Octet Rule Lewis theory says that atoms most stable when they have their octet of valence electrons Some violate this rule Be 2 bonds with no lone pairs B9 3 bonds with no lone pairs 3rd row elements often ignore the octet rule and more than eight electrons odd electron species unpaired electrons freeradicals Lewis Structure Memorize common bonding pattern Picture Writing Lewis Structures from Molecular Compounds in 5 STEPS 1 Draw correct skeleton structure for molecule 2 calculate total of valence electrons add an extra electron for each negative charge subtract an electron for positive charge 3 Place two bonding electrons between each bonding atom Then try to fill the valence shell of atoms by adding electrons Start with the terminal atoms first 4 If any atoms lack an octet for double or triple bonds do this by moving electron pairs from terminal atoms into the bonding regions 5 check your work total number of electrons added to the Lewis structure should number of electrons in step 2 EX O 5 F0 g i 1 6V 4 6 l FOZHWOa lI50 flv39ol p 09 H 0 4 39t l mm mm ammt 3 53 H A C 1 D39L l 39 OU 7 0 z w 0 quotl W2 0 WM I 0 04601 0 l 3 Z I l 2 N971 an 0 75000 0 L1 1 0 g g 3 N 0 7 V quot39 F6 2 v 4 9 0 t N 5 wifgfwl o 7 W T Fiji 10 mm 1 olt501m 4 V might v 5mg cHCW format qu at I O39x Miw v39 5 Formal Charge During bonding atoms may end With more or fewer electrons than the valence electrons have brought in order to fulfill octets results in atoms having a formal charge FC starting With valence electrons nonbonding electrons 12 bonded electrons
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