Problem Sets 3 Chapters 12 13 1 Which of the following statements concerning dipole dipole attractions is correct a Dipole dipole attraction is a weaker force than covalent bonds being about 50 as strong b Dipole dipole attractions increase as the distance between the dipoles increase c Dipole dipole attractions are weak due in part to the fact that the charges associated with dipoles are only partial rather than full charges d All the above statements are correct e None of the above statements are correct 2 Which one of the following molecules is the most polarizable a H3C I d H3C H e H3C OH b H3C CH3 c H3C F Note On an exam I might ask you to the order of boiling points lowest to highest for these 5 compounds 3 For a series of small molecules of comparable molecular mass which of the following choices lists the intermolecular forces in the correct increasing order a dipole dipole forces London forces hydrogen bonds b hydrogen bonds dipole dipole forces London forces c dipole dipole forces hydrogen bonds London forces d London forces dipole dipole forces hydrogen bonds e hydrogen bonds London forces dipole dipole forces 4 The order of the boiling points for the hydrogen halides except for HF is HI HBr HCl The reason for this order can be attributed to a the relative covalent bond strengths b differences in hydrogen bonding c differences in dipole dipole attractions d differences in London forces e differences in dipole induced dipole interactions 5 Which compound below would be expected to have the highest boiling point a CH3 CH2 CH2 CH2 CH2 CH2 CH3 b CH3 CH2 CH2 CH2 CH CH3 CH3 c CH3 CH CH2 CH CH3 CH3 CH3 CH3 d CH3 CH C CH3 CH3 CH3 6 Three factors control the rate of evaporation of a liquid surface area temperature and strengths of intermolecular forces More than one of the statements given described a correct effect The statements are 1 the larger the surface area the faster the rate of evaporation of the liquid 2 the higher the temperature the faster the rate of evaporation of the liquid and 3 the stronger the intermolecular attractive forces the faster the rate of evaporation of the liquid Which choices are correct a choices 1 and 2 b choices 1 and 3 c choices 2 and 3 d all three choices are valid and describe a correct effect e none of the three choices describe a correct effect G 43 8 o C J 93 7 o C M 56 7 o C T 83 5 o C R 63 6 o C 7 Given the following substances and their normal boiling points in o C Which set below correctly lists some of these liquids in order of increasing intermolecular forces at 20 oC a G R J b J T R c R T G d G J M e J R M 8 Where in the phase diagram of a compound do all phases exist together a at the sublimation point b at the boiling point c at the melting point d at the critical point e at the triple point 9 Which of the following molecular solids will exhibit dipole dipole intermolecular forces NH3 BF3 I2 and H2S a NH3 and H2S correct b NH3 BF3 and H2S BF3 has polar bonds but is a nonpolar molecule c I2 only d BF3 and I2 e NH3 BF3 I2 and H2S 10 Which of the following properties of water can be explained using hydrogen bonding arguments 1 its ability to dissolve most ionic compounds 2 its high boiling point 3 its low vapor pressure a only 1 or only 2 or only 3 b 1 and 2 only c 1 and 3 only d 2 and 3 only e 1 and 2 and 3 ANSWERS 1 C 2 A 3 D 4 D 5 A 6 A 7 A 8 E 9 A 10 E