PRINCIPLES OF CHEMISTRY I
PRINCIPLES OF CHEMISTRY I CH 301
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This 12 page Class Notes was uploaded by Brady Spinka on Monday September 7, 2015. The Class Notes belongs to CH 301 at University of Texas at Austin taught by Deborah Walker in Fall. Since its upload, it has received 7 views. For similar materials see /class/181879/ch-301-university-of-texas-at-austin in Chemistry at University of Texas at Austin.
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Date Created: 09/07/15
This print out should have 57 questions Multiple choice questions may continue on the next column or page 7 nd all choices before answering It is better to understand the underlying reasons behind the periodic trends than to memorize the trends This is because we will apply the trends to other future topics 001 01 points For the reaction 7C6H6702 gt7COQ7HQO 446 grams of C6H6 are allowed to react with 1521 grams of 02 How much 00 will be produced by this reaction Correct answer 1508 grams Explanation HICSH6 446 g mo2 1521 g The balanced equation for the reaction is 206H615OQ gt120026HQO FW of C6H6 is 781118 gmol7 giving 0571 mol C6H6 FW of 02 is 319988 gmol7 giving 4753 mol 02 FW of CO is 440095 gmol 0571 10 H gtlt 151110102 mo 6 6 2 mol C6H6 4282 mol 02 which is less than what is actually present Therefore the limiting reactant must be C6H6 12 mol 002 0571 1 C H mo 6 6 X2moio6H6 X 440095 g 002 1 mol CO 002 01 points Which of the following could we describe as isoelectronic with Cl 1508 g 002 1 Ar correct 2 S 3 Ca 4 Rb Explanation The number of electrons in each particle is as follows 8 17 Ar 1 18 Cl 18 Ca L 19 Rb 37 003 01 points The n and 4 quantum numbers of the last electron of an element are n 4 and 0 The element is 1 a d transition metal 2 a noble gas 3 a nonmetal 4 an f transition metal 5 a representative element correct Explanation The value of 4 07 so the electronic con guration must contain an s orbital The representative elements are elements in which the last electron added was to an s or p or bital7 so the element must be a representative element 004 01 points In reactions to form ionic compounds7 metals generally 1 become non metals 2 lose electrons correct 3 gain electrons 4 do not react Explanation lonic bonds occur between metals and non metals Metals will generally lose electrons7 as the nonmetals will generally receive electrons 005 01 points Which of the following does NOT have a lled valence shell 1 A1 2 F 3 N2 correct 4 Ne 5 K Explanation N has ve valence electrons7 so N2 would have three 006 01 points Rank the following species from smallest to largest atomic radius K7 Mg7 Rlo7 Ca 1 Mg lt Ca lt K lt Rb correct 2RbltKltCaltMg 3MgltKltCaltRb 4MgltCaltRbltK 5MgltRbltKltCa Explanation Atomic radii increase down and to the left 007 01 points Which symbols in the periodic table represent elements having 7 valence electrons 1 R 2 Q 3 P and L correct 4Y 5 XandZ Explanation The halogens have seven valence electrons 008 01 points The correct Lewis dot structure for HCl is 1 2H Ki 2 H 1 correct 3 H Cl 4 H 351 Explanation Cl forms one covalent bond to H in order to complete its octet 009 01 points The Lewis dot structure for sulfur has 1 three pairs of electrons and one lone elec tron 2 one pair of electrons and three lone elec trons 3 two pairs of electrons and two lone elec trons correct 4 three pairs of electrons 5 two pairs of electrons and one lone elec tron Explanation S has 6 valence electrons The rst 2 elec trons pair as they would in the s orbital The following 3 electrons are placed unpaired as they would in the p orbital The last electron pairs up with one of the unpaired ones7 giving 2 paired electrons and two lone electrons 010 01 points Which of the following is the correct Lewis structure of magnesium chloride MgClg 1 Mg2 2 361 7 correct N ngi 1 GO 2iAg22 4 El 1 5Mg Explanation 011 01 points How many bonding and lone pairs does the carbon in CF4 have 1 4 and4 2 4 andl 3 0 and4 4 4 and2 5 4 and 0 correct Explanation The total number of valence electrons is C lgtlt467 46 F 4X7CT2867 326 The Lewis structure is 012 01 points In carbon containing compounds7 carbon usually forms 1 four bonds7 nitrogen usually forms three bonds7 oxygen usually forms two bonds7 and hydrogen only forms one bond correct 2 three bonds7 nitrogen and oxygen usually form two bonds7 and hydrogen only forms one bond 3 four bonds7 nitrogen usually forms ve bonds7 oxygen usually forms six bonds7 and hydrogen only forms one bond 4 four bonds7 nitrogen and oxygen usually form two bonds7 and hydrogen only forms one bond Explanation These bonding schemes C39 N I allow each atom except H to have a complete octet of valence electrons o H 013 01 points Which of the following exhibits resonance while strictly obeying the octet rule 1Hgo 2 NO correct 3 0103 4 02 Explanation The structure for the NO ion is This is a resonance structure because the double bond could be placed at any of the O atoms 014 01 points Which of the following contains exactly 2 un shared pairs of valence electrons 1 PH3 2 SiH4 3 CQH4 4 H28 correct 5 NaCl Explanation The HQS molecule contains exactly 2 un shared pairs of valence electrons H H You can check this structure for correctness by verifying that each atom has the correct number of electrons around it 8 for most ele ments7 2 for hydrogen and that the structure shows the correct total number of valence elec trons calculated by adding up the available valence electrons from each atom The CQH4 molecule contains no unshared pairs SiH4 contains no unshared pairs NaCl an ionic compound contains 4 unshared pairs and PH3 contains 1 unshared pair 015 01 points How many lone pairs of electrons are on nitrogen in NFg 1 two 2 none as three 5 four 63 thirteen q twenty 8 one correct Explanation The Lewis structure is quot i F 016 01 points Which one of the following compounds does NOT obey the octet rule 1 CH4 2 BF3 correct 3 NaCl 4 H20 Explanation 017 01 points The molecular formula for phosgene is 000127 with carbon being the central atom Select the correct response 1 There is 1 bond between carbon and oxy gen7 and 3 pairs of non bonding electrons on oxygen 2 There are 2 bonds between carbon and oxygen7 and 1 pair of non bonding electrons on oxygen 3 There is 1 bond between carbon and oxy gen7 and 2 pairs of non bonding electrons on oxygen 4 There are 3 bonds between carbon and oxygen7 and 1 pair of non bonding electrons on oxygen 5 There are 2 bonds between carbon and oxygen7 and 2 pairs of non bonding electrons on oxygen correct Explanation The Lewis dot structure is 018 01 points Which of these substances has a formula incorporating a triple bond 1 HOF 2 BFg 3 B13 4 H288 5 CQFQ correct 6 H01 7 H200 8 H20 9 B013 10 H28 Explanation The structure for CQFQ is C E C Each C brings in 4 valence 6 and each F brings in 77 for a total of 22 6 The octet rule is satis ed for each atom 019 01 points The ion BeF has a total of 7 shared electrons and 7 non bonded electrons 162 222 342 4 2 4 5 2 8 correct 6 44 9 63 Explanation Be is one of the exceptions to the octet rule The total number of valence electrons is Be 7 1X26 1gtlt7e 167 HKIN 6 6 6 F 71 charge 10 6 The Lewis Dot structure is Bei 020 01 points Which of the following would be expected tc have chemical properties similar to those 0 sulfur 1 Se correct 2 Ar 3 Mg 4 Si 5 P 6F Explanation 021 01 points Rank the following species from least tc greatest polarizability As7 Li7 l7 Rn7 Al 1AlltAsltlltRnltLi 2RnltLiltAlltAsltl 3 Li lt Al lt As lt l lt Rn correct 4AsltIltRnltLiltAl 5IltRnltLiltAlltAs Explanation Polarizability of neutral species is simply a function of total electron count More elec trons equates to greater polarizability 022 01 points Which of the following atoms has the greatest electron af nity 1 arsenic 2 uorine correct 3 sulfur Explanation Electron af nity is a measure of how readily a neutral atom will accept an electron to form a 71 ion The higher the EA the more readily this occurs Higher7 may mean more positive7 or more negative7 depending on how this has been de ned by your professor The GENERAL trend is EA will increase from left to right and from bottom to top Group VH elements have the highest values as they only need one more electron to complete an octet 023 01 points Which atom selenium Se or Arsenic As has the higher electron af nity and why 1 Arsenic because it has a stable half lled p subshell and adding an electron increases its stability 2 Selenium because it does not have a sta ble half lled p subshell and adding an elec tron does not decrease its stability correct 3 Selenium because it has a lower effective nuclear charge 4 Arsenic because it has a lower effective nuclear charge 5 Neither because selenium and arsenic have the same electron af nity Explanation Arsenic electron af nity 79 has a a half lled p subshell and one additional elec tron does not increase its stability in fact it perturbs it from a relatively stable con gu ration Selenium electron af nity 195 is moved slightly close to a lled shell and no ble gas con guration by addition of a single electron and sacri ces no half lled stability in the process 024 01 points Which ion has the larger radius 1 SeQ 2 Both have same radius 3 Unable to determine 4 As37 correct Explanation Ionic radii become larger as you move down a column or as you move from right to left across a row 025 01 points Which of the following is true about the fol lowing list of species Br SeQT Kr Rb 88 1 They are listed in order of increasing electronegativity 2 They are listed in order of decreasing electronegativity 3 They are isoelectronic correct 4 They are listed in order of increasing number of electrons 5 They are listed in order of decreasing number of electrons Explanation Each of these species has 36 electrons They are isoelectronic 026 01 points What is the correct order of increasing elec tronegativity 1 07 C7 N7 S7 P7 Si7 F 2 F7 07 N7 C7 S7 P7 Si 3 Si7 P7 S7 C7 N7 07 F correct 4 F7 Si7 P7 S7 N7 C7 0 Explanation Generally speaking electronegativity in creases frorn left to right across the periodic table and from bottom to top for elements within a group Si19 lt P22 lt S26 C26 lt N30 lt C34 lt F40 027 01 points The letters in the periodic table are used to identify four different elements Based on periodic table trends7 which el ernent is expected to have the GREATEST tendency to attract a shared pair of electrons 1 A 2 B 3 C correct 4D Explanation Electronegativity the ability to attract a shared pair of electrons increases going to the right and upward in the periodic table 028 01 points Rank the following from least to greatest ion ization energy silicon Si7 phosphorous P7 sulfur 1 P lt Si lt S 2 S lt Si lt P 3 Si lt S lt P correct 4 Si lt P lt S 5 S lt P lt Si 6 P lt S lt Si Explanation ionization energy increases increases across a given row7 but because of the added sta bility of a half lled p subshell7 sulfur has a lower ionization energy than would be simply predicted based on effective nuclear charge argurnents 029 01 points The electronegativity of H is 1 about equal to that of C correct 2 a lot more than that of C 3 a lot less than that of C Explanation 030 01 points The octet rule indicates that 1 atoms are most stable when involved in formation of eight bonds 2 all of the other responses are false 3 atoms prefer the octahedral electronic ge ornetry 4 most atoms are stabilized by a lled outer s and p shell correct 5 atoms gain or lose electrons to form bond ing orbitals Explanation The octet rule states that atoms in com pounds are generally most stable when they achieve noble gas con gurations Noble gases have lled outer s and p orbitals Since an s orbital can hold two electrons and a p orbital is lled with 6 electrons this is a total of 8 valence electrons 031 01 points Select the set of bonds below that lists in order an ionic bond polar covalent bond and and a nonpolar covalent bond 1N00HCH 2KOH7FC7H 3 BriBrCiHNaiS 4 Nais BriBrCiH 5NaiSCiHBriBr correct Explanation An ionic bond is formed when two sub stances of very different electronegativity form a bond 7 usually a metal and a non metal A polar covalent bond results when two substances of low to moderate differences in electronegativity form a bond When two of the same atoms bond or when two atoms having the same electronegativity bond the result is a nonpolar covalent bond as long as neither substance is a metal 032 01 points Compounds which are characterized as cova lent are generally made up of elements found in which part of the Periodic Table 1 left and right 2 upper left 3 upper right correct 4 lower left Explanation Covalent compounds are formed from ele ments with smallA E N or nonmetal elements These are found in the upper right corner of the periodic table Very metallic elements are found in the lower left corner of the periodic table 033 01 points When magnesium reacts with chlorine the reaction involves a 1 transfer of electrons from Cl to Mg 2 creation of electrons 3 sharing of electrons between Mg and Cl 4 transfer of electrons from Mg to Cl cor rect Explanation 034 01 points On the Pauling scale the HF and NaBr bonds both have an electronegativity difference of 19 But although HP is a vaguely water like liquid which boils at 19 C NaBr is a typical ionic solid which melts at around 7500 C and boils at around 14500 C What is the best explanation for this 1 Other factors in addition to electronega tivity play a part in determining whether or not a given substance will be ionic correct 2 Witchcraftl Call Winona Ryder Hurryl 3 The Pauling electronegativity scale is hor ribly wrong 4 The data for HP and NaBr are horribly wrong Explanation Other factors which determine the type of bonding between two elements include ioniza tion energies electron a inities atomization energies and crystal lattice energy 035 01 points How does a large electronegativity difference affect molecular properties 1 It makes the bonds highly polar 2 If molecular geometry permits7 it makes the molecule highly polar 3 All choices are correct correct 4 It makes the bonds stronger and shorter than otherwise expected Explanation 036 01 points Coordinate covalent bond formation is a pro cess in which 1 one atom gives up an electron to another atom 2 one electron in the covalent bond is sup plied by each atom 3 one atom gives up more than one electron to another atom 4 two atoms share more than one pair of electrons 5 both electrons in the covalent bond are supplied by the same atom correct Explanation All covalent bonds involve the sharing of electrons7 so we can rule out the two answer choices that involve the transfer of electrons where one atom gives electrons to another atom When two atoms share more than one pair of electrons it would result in a double or triple bond The correct answer is that a coordinate covalent bond is a bond in which one atom supplies both of the electrons for the bond 037 01 points Which of the following is the best description of covalent bonding 1 Bonding that occurs between elements with similar electronegativities7 and with transfer of electrons 2 Bonding that occurs between elements with very different electronegativities7 and with sharing of electrons 3 Bonding that occurs between ions and elements7 and with the sharing of electrons 4 Bonding that occurs between elements with very different electronegativities7 and with transfer of electrons 5 Bonding that occurs between elements with similar electronegativities7 and with sharing of electrons correct Explanation 038 01 points Which of the following contains both covalent and ionic bonding 1 CQF4 2 002 3 NaNOg correct 4 KF 5 CH4 Explanation For NaNOg the N70 bonds are covalent and the NaiN bond is ionic 039 01 points In the compound MgS7 the sul de ion has 1 lost one electrons 2 gained two electrons correct 3 lost two electrons 4 gained one electron Explanation If you locate sulfur on the periodic table7 it is in Group Vl as a nonmetal The elements in Group Vl would like to gain two electrons in order to be stable Magnesium is a metal in Group H the elements in Group H would like to lose two electrons in order to be stable The sulfur atom has gained two of magnesium7s electrons to become the sul de ion 040 01 points An element E has the electronic con gura tion 132 2s2 24 What is the formula of its compound with lithium 1 LigE correct 2 LiE 3 Li4E 4 LiEg Explanation E is oxygen since it has six valence elec trons7 it forms a 27 ion isoelectronic with Ne 041 01 points Which of the following bonds is strongest 1NO 2 CO correct 3 C C 4 NN Explanation 042 01 points A free radical will readily due to its 7 1 react lone electron pair 2 decompose high stability 3 react highly energetic nature correct 4 not react unstability Explanation Free radicals are very energetic and reactive particles that have an unpaired electron 043 01 points How many electrons do we expect to do chem istry for an Al atom 1 5 2 13 3 2 4 3 correct 51 Explanation 044 01 points Consider the bonds in ironlll oxide Are the bonds more ionic or more covalent 1 lonic correct 2 Covalent Explanation Bonds between metals like iron and non metals like oxygen are most likely ionic 045 01 points How many valence electrons are there in one ozone molecule Correct answer 18 Explanation Each oxygen atom has 6 valence electrons total electrons 3 X 6 6 each 0 atom 18 6 046 01 points Which atom in the molecule partially positive CiBr is 1 Br 2 C correct Explanation 047 01 points Given that elements C and S are bonded and the electronegativity difference is 00 deter mine the bond type and the more negative atom 1 nonpolar covalent bond C 2 ionic bond S 3 ionic bond same electronegativity 4 polar covalent bond S 5 polar covalent bond same electronegativ ity 6 None of these 7 nonpolar covalent bond S 8 nonpolar covalent bond same electroneg ativity correct 9 ionic bond C 10 polar covalent bond C Explanation Electronegativity difference 00 Electronegativity difference of 0 to 03 gives a nonpolar covalent bond 3 similarities in attractions for shared elec trons when the electronic and molecular ge ometries are the same 4 atoms that are bonded together but have unequal numbers of lone pair electrons 5 the optimal Lewis dot structure for any pair of atoms Explanation Polarity arises from an unequal sharing of electrons 049 01 points Consider a series of molecules in which carbon is bonded to second period elements 070 0 F C iN and 070 Rank these bonds from least polar to most polar 1 07F lt 070 lt CiN lt 070 2 CiC lt CiN lt CiF lt 070 3 Cic lt CiN lt 070 lt 07F cor rect 4 CiO lt CiN lt CiF lt CiC Explanation The most ionic bond will have the high est difference in electronegativity between the two atoms Since one of these atoms is al ways carbon in this question the order will be of carbon bonded to molecules of increas ing electronegativity Electronegativity in creases across a row so the order of increasing ionic polar character will be 070 CiN 070 and then CiF 048 01 points The concept of polarity is due to 1 one atom of a bonded pair of atoms ex erting a greater attractive force on the shared electrons correct 2 the number of electrons shared by any pair of atoms 050 01 points You would expect a nitrogen oxygen bond to be 1 polar with the nitrogen end having a partial negative charge 2 polar with the oxygen end having a par tial negative charge correct 3 non polar with neither end having a par tial charge 4 polar with neither end having a partial charge 5 non polar with the oxygen end having a partial negative charge 6 non polar with the nitrogen end having a partial negative charge Explanation 051 01 points Which covalent bond is the most polar 1H7N 2 H7O correct 3 H 7S 4 H 7 H Explanation In each case a pair of electrons is being shared between H and one other element The greater the difference in electronegativity be tween the two elements H and O N H and S the more polar the bond Electroneg ativity increases going from left to right and upward in the periodic table so the most elec tronegative element is 0 meaning the H70 bond is most polar 052 01 points You would expect a phosphorous chlorine bond to be 1 nonpolar with the phosphorus end having a partial negative charge 2 polar with neither end having a partial charge 3 nonpolar with the chlorine end having a partial negative charge 4 polar with the phosphorus end having a partial negative charge 5 nonpolar with the neither end having a partial charge 6 polar with the chlorine end having a partial negative charge correct Explanation 053 01 points Which pair of bonded atoms has the largest dipole moment 1 N 7 N 2 C 7 O 3 C 7 F correct 4 C 7 N 5 C 7 C Explanation Dipole moments result because of the differ ence in electronegativity EN between bond ing atoms The bonds with the largest dipole will have the largest difference in EN EN in creases from bottom to top and left to right on the periodic table C 7 C and N 7 N have the same EN so there is no dipole moment Between N O and F F is the most EN and has the largest difference in EN with C Therefore the C 7 N bond has the largest dipole 054 01 points Using charge density rank the following com pounds by lattice energy from least to great est Kl CaSe BeO FrAt 1 Kl lt BeO lt FrAt lt CaSe 2 FrAt lt Kl lt CaSe lt BeO correct 3 BeO lt CaSe lt Kl lt FrAt 4 Kl lt ErAt lt BeO lt CaSe
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