Dipole Moment Ch 5-6 Answer Key

Chapter 5 study guide DIPOLE MOMENT Definition – The MEASURED VALUE with the SEPARATION of PARTIAL POSITIVE AND PARTIAL NEGATIVE CHARGES in a MOLECULE - Farther = Larger = Higher percentage ionic character - Closer = Weaker = Lower percentage ionic character Ex. Identify the compound with the largest dipole moment in the gas phase. A) Cl2 B) ClF C) HF D) LiF 6) Identify the compound with the smallest dipole moment in the gas phase. A) Cl2 B) ClF C) HF D) LiF ) Identify the compound with the highest percent ionic character. A) HF B) IBr C) HCl D) LiF Answer: D Diff: 1 Var: 1 Page Ref: 5.2 Global: G2 8) Identify the compound with the smallest percent ionic character. A) HF B) IBr C) HCl D) LiF FORMAL CHARGE Formal charge is the charge of an atom that it would have if all bonding electrons were shared equally between the bonded atoms IONIC CHARACTER INCREASE ACROSS PERIOD INCREASE DOWN GROUP Ex. Using periodic trends, place the following bonds in order of increasing ionic character. S-I Se-I O-I A) Se-I < S-I < O-I B) S-I < Se-I < O-I C) O-I < Se-I < S-I D) Se-I < O-I < S-I E) O-I < S-I < Se-I 10) Using periodic trends, place the following bonds in order of decreasing ionic character. Sb-Cl P-Cl As-Cl A) Sb-Cl > As-Cl > P-Cl B) As-Cl > Sb-Cl > P-Cl C) Sb-Cl > P-Cl > As-Cl D) P-Cl > As-Cl > Sb-Cl E) As-Cl > P-Cl > Sb-Cl TYPES OF BONDS FIND IT BY SUBTRACTING ELECTRONEGATIVITIES PURE = 0 NONPOLAR COVALENT = 0.1 - 0.4 POLAR COVALENT = 0.5 – 1.9 IONIC = 2.0+ Ex. Which molecule or compound below contains a pure covalent bond? A) Li2CO3 B) SCl6 C) Cl2 D) P Br3 E) Li F 12) Which molecule or compound below contains a polar covalent bond? A) C2H4 B) MgS C) K F D) NI3 E) Ag Cl 13) Which molecule or compound below contains an ionic bond? A) C S2 B) C2Cl4 C) Si F4 D) OCl2 E) NH4NO3 14) The electronegativity is 2.1 for H and 1.9 for Sb. Based on these electronegativities SbH3 would be expected to A) be ionic and contain H- ions. B) be ionic and contain H+ ions. C) have polar covalent bonds with a partial negative charges on the H atoms. D) have polar covalent bonds with a partial positive charges on the H atoms. E) have nonpolar bonds BOND ORDER (# ELECTRONS IN BONDING – ELECTRONS NOT IN BONDING)/2 INCOMPLETE VS EXPANDED OCTECTS INCOMPLETE = LESS THAN 8 ELECTRONS EXPANDED = OVER 8 ELECTRONS ELEMENTS FROM ROW 3 AND BELOW CAN HAVE EXPANDED OCTECTS Ex. Which of the following elements can form compounds with an expanded octet? A) As B) C C) Li D) F E) All of the above elements can form compounds with an expanded octet. 22) Which of the following elements can form compounds with an expanded octet? A) N B) I C) F D) Be E) None of the above can form compounds with an expanded octet. 23) How many of the following elements can form compounds with an expanded octet? I O Br Si A) 2 B) 0 C) 3 D) 1 E) 4 LEWIS STRUCTURE - USE FORMAL CHANGE WHICHEVER WITH LEAST BONDS IS BETTER Ex. 20) Choose the best Lewis structure for SF4. A) B) C) D) E) 21) Choose the best Lewis structure for BF3. A) B) C) D) E) Exceptions: RED QUESTIONS!!! Consider the molecule below. Determine the molecular geometry at each of the 2 labeled carbons. A) C1 = tetrahedral, C2 = linear B) C1 = trigonal planar, C2 = bent C) C1 = bent, C2 = trigonal planar D) C1 = trigonal planar, C2 = tetrahedral E) C1 = trigonal pyramidal, C2 = see-saw Consider the molecule below. Determine the molecular geometry at each of the 3 labeled atoms. A) 1 = trigonal planar, 2 = tetrahedral, 3 = trigonal pyramidal B) 1 = tetrahedral, 2 = tetrahedral, 3 = tetrahedral C) 1 = trigonal planar, 2 = tetrahedral, 3 = tetrahedral D) 1 = tetrahedral, 2 = tetrahedral, 3 = trigonal planar E) 1 = trigonal planar, 2 = trigonal pyramidal, 3 = trigonal pyramidal Rank the following molecules in decreasing bond energy. Br2 F2 I2 Cl2 A) I2 > Br2 > Cl2 > F2 B) Cl2 > Br2 > F2 > I2 C) I2 > Cl2 > Br2 > F2 D) Cl2 > I2 > F2 > Br2 Answer: B BONDS AND THEIR TRENDS Length: MORE ATOMS = INCREASE SHORT RESPONSE QUESTIONS 7) Draw the Lewis structure for the acetate ion, CH 3CO2⁻, including any important resonance structures. Label each atom with its formal charge. Answer: There should be two equivalent resonance structures drawn. All atoms should have a formal charge of "0" except the singly bonded O will have a formal charge of -1. 8) Draw the Lewis structure for BrO3-. Make sure to include any important resonance structures. Answer: Three equivalent resonance structures should be drawn, each containing 1 single Br-O bond and 2 double Br-O bonds. Bromine has a lone pair, each double-bonded oxygen has two lone pairs, and the single-bonded oxygen has three lone pairs. 10) Define bond energy. Answer: Bond energy is the energy required to break 1 mole of the bond in the gas phase. 11) Is it possible for a molecule to be nonpolar even though it contains polar bonds? Explain your answer and give an example. Answer: Yes. The polarity of a molecule depends on the molecular geometry and whether or not all of the dipoles (polar bonds) cancel one another. If the molecular geometry causes all of the dipoles to cancel, the molecule will be nonpolar. An example is CF4 where there are four polar bonds, but the dipoles sum to 0 making the molecule nonpolar. 12) Explain why oil and water do not mix. Answer: Water molecules are polar and oil molecules are not polar. 13) Determine the molecular geometry about each interior atom in the following structure. Sketch the three-dimensional structure and label the interior atoms with the corresponding molecular geometry. CH2CHCCCH3 Answer: The sketch should show all of the appropriate multiple bonds, with a double bond between carbons 1 and 2 and a triple bond between carbons 3 and 4. The first two carbons are trigonal planar, the second carbons are linear and the last carbon is tetrahedral. Chapter 6 Study guide HYBRIDIZATION DETERMINED BY THE # OF BONDS MOST STABLE = LEAST ELECTRONS MOLECULAR ORBITAL DIAGRAM 1. 2. 3. 4. 5. FIND ELECTRON CONFIGURATION DRAW IT OUT WITH THE DASHES DRAW LEWIS STRUCTURE BOX THE S ORBITAL WITH NECESSARY # OF P ORBITALS FILL IN DIAGRAM FROM ENDS, THEN BOTTOM TO TOP Ex. Use the molecular orbital diagram shown to determine which of the following is MOST stable. A) C22⁺ B) N22⁺ C) B2 D) C22⁻ E) B22⁺ Use the molecular orbital diagram shown to determine which of the following is LEAST stable. A) C22⁺ B) O22⁺ C) B2 D) C22⁻ E) B2⁺ SIGMA & PI BONDS SIGMA = SINGLE BONDS & END TO END P ORBITAL PI = DOUBLE BONDS & SIDE TO SIDE P ORBITAL ) Consider the following compound. How many sigma and pi bonds does it contain? CH3CHCHCO2H A) 9 sigma, 4 pi B) 11 sigma, 2 pi C) 9 sigma, 2 pi D) 13 sigma, 2 pi E) 6 sigma, 2 pi 25) Draw the Lewis structure for the molecule C3H4. How many sigma and pi bonds does it contain? A) 7 sigma, 1 pi B) 8 sigma, 1 pi C) 6 sigma, 2 pi D) 10 sigma, 2 pi E) 8 sigma, 2 pi RED QUESTIONS Consider the molecule below. Determine the hybridization at each of the 2 labeled carbons. A) C1 = sp3, C2 = sp2 B) C1 = sp2, C2 = sp2 C) C1 = sp2, C2 = sp3d D) C1 = sp3d , C2 = sp3d E) C1 = sp2, C2 = sp3 13) Consider the molecule below. Determine the hybridization at each of the 3 labeled atoms. A) 1 = sp2, 2 = sp3, 3 = sp2 B) 1 = sp2, 2 = sp3, 3 = sp3 C) 1 = sp3, 2 = sp3, 3 = sp3 D) 1 = sp3, 2 = sp3, 3 = sp2 E) 1 = sp , 2 = sp , 3 = sp2 2) Determine the hybridization about each interior atom in the following structure. Sketch the three-dimensional structure and label the interior atoms with their corresponding hybridization. CH2CHCCCH3 Answer: The sketch should show all of the appropriate multiple bonds, with a double bond between carbons 1 and 2 and a triple bond between carbons 3 and 4. The first 2 C's are sp2 hybridized, the next 2 C's are sp hybridized and the last C is sp3 hybridized. 3) According to molecular orbital theory, what is an antibonding orbital? Answer: An antibonding orbital is formed when 2 orbitals destructively interfere with eachother