1) Identify the main intermolecular force acting between the following molecules: 4+4=8. (g) (h) Ionic Bonding Dipole-Dipole. (j) N. polar.

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1 CEMISTRY 11 AP INTERMOLECULAR ORCES WORKSEET 1) Identify the main intermolecular force acting between the following molecules Licensed to Walnut Grove Secondary for school use only from September to June (a) C Valence E O (g) C * C t tetrahedral (b) (e) London (dispersion) forces DipoleDipole London (dispersion) forces C O C N S ydrogen Ibonding (h) (k) DipoleInduced Dipole S C DipoleDipole (c) Al (i) 3 O ftpj#3tciii C I tci5sn/r?pjrtrigonalbipyramidalisrthpjr Ionic Bonding DipoleDipole (d) (j) N 2 Valence octahedral Valence London (dispersion) forces Nitrogen tribromide DipoleDipole e NN linear

2 0 (f) (l) Si 4 valence E i i" sit tetrahedral IonDipole force London (dispersion) forces 2) Predict which compound in each pair will have the higher melting point/boiling point Explain your answer (a) CS 2 or C 4 CS2 valence e CC Valence e q;&l p c ci linear I on C ntetrahedral C 4 Since both are the compound that has the stronger London (dispersion) forces will have the higher MP/BP London (dispersion) forces get stronger as the molecular mass increases valence E I ie?iktcii2&2va1encee (b) I or KI KI KI has ionic bonds while I possesses weaker dipoledipole forces (c) 2 or D 0 6 G 0 + x e 6 a 2 Since both are the compound that has the stronger London (dispersion) forces will have the higher MP/BP London (dispersion) forces get stronger as the molecular mass increases

3 C (d) Na 2 O or 2 O sovalenceei [ Nail D] [ NAI % bent st s st Na 2 O Na 2 O has ionic bonds while 2 O possesses weaker hydrogen bonding (e) SiO 2 or CO g g 902 valence e si0 Cckvalencee linear O C O SiO 2 SiO 2 is a network covalent solid so covalent bonds would need to be broken while CO 2 has weak London (dispersion) forces (f) C 4 or N 3 µ 1 t Ctkvalencee Ntbvalencee tetrahedral g ql siingtrigonal #pyramidal g+ stt of N 3 N 3 has hydrogen bonding while C 4 possesses weaker London (dispersion) forces (g) C 3 or C 4 CA }uakncee &??jeg µ * name " 4+28 ro#fpittftfaahredra a C 3 C 3 has dipoledipole forces while C 4 possesses weaker London (dispersion) forces tetrahedral

4 Polar (h) B 3 or P 4 P 4 Since both are the compound that has the stronger London (dispersion) forces will have the higher MP/BP London (dispersion) forces get stronger as the molecular mass increases (i) Ca 2 or 618 you may think Btzvalencee Pyvalenoee trigonalplanar p p isthis B when infaotit s P ~ both of / \ p ; this fualencee ftptshfnoture " P Pare them P EEICCATTEEI SI Ca 2 Ca 2 has ionic bonds while possesses weaker hydrogen bonding 3) The industrial production of ammonia N 3 from 2 and N 2 is called the aber process named for ritz aber the German chemist who developed it just before World War I During the process in a gaseous mixture of all three substances N 3 must be separated from 2 and N 2 This is done by cooling the gaseous mixture so as to condense only the N 3 This leaves the elemental nitrogen and hydrogen as gases to be recycled and produce more ammonia Why does only the ammonia liquefy upon cooling but not the 2 or N 2? Since hydrogen bonds exist between ammonia molecules but only London (dispersion) forces exist between diatomic molecules of nitrogen and hydrogen the ammonia has a higher boiling point and therefore liquefies (condenses) at a higher temperature than nitrogen and hydrogen that remain in the gaseous phase upon cooling 4) Rank the following compounds from weakest intermolecular forces to strongest Justify your answers asvalencee 2 S I 2 N 2 2 O 8T say st si!? 1028 N±N ben a N 2 and I 2 are so they only have London (dispersion) forces I 2 has stronger forces since it is larger 2 S has dipoledipole forces therefore it is stronger than I 2 2 O has hydrogen bonding therefore it is stronger than 2 S N 2 < I 2 < 2 S < 2 O aovalencee MY?fet2t2N2valenceej sioiqbent sty

5 5) Rank the following from weakest intermolecular forces to strongest Justify your answers all valence E ^ 2 Se 2 S 2 Po 2 Te v5 oio#opdar 8T Paige "qa3 0h s si benf 8T bent bent set Pos Te These compounds are all the same bent shape Although 2 S is slightly more than the others it is not very so it has very weak dipoledipole forces Therefore the differences in London (dispersion) forces are more important for these compounds 2 Po is the largest and therefore has the strongest London (dispersion) forces 6) Iodine is a diatomic molecule yet its molecules have enough attraction for each other that the element exists as a solid at room temperature Identify the attractive force and explain why it is strong enough to keep the molecules of I 2 attached to each other even at room temperature I 2 is a relatively large and massive diatomic molecule and the strength of London dispersion forces increases as the size of the molecules involved increases This is because large electron clouds are more loosely held than smaller clouds and therefore more easily deformed or ized by a nearby dipole than compact tightly held clouds In addition large molecules with more surface area have electron clouds that are spread out and so are more easily distorted by neighbouring dipoles As a result the dispersion forces are strong enough to keep the molecules of I 2 attached to each other even at room temperature 7) Surface tension is the ability of a fluid to act as a thin elastic membrane at its surface Explain why molecules usually have much lower surface tension than ones Surface tension results when the molecules at a surface attract each other to be able to form a thin elastic membrane or example 2 O (due to their hydrogen bonding) has surface tension since the positive hydrogen pole of one water molecule is attracted to the negative oxygen pole of a neighbouring water molecule tbent Since molecules are not attracted to each other as much as in molecules these molecules are much less likely to have high surface tension

6 8) Ionic compounds such as Na have very high melting points because a great deal of energy is required to overcome the many attractive forces between the oppositely charged ions in an ionic crystal lattice Na melts at 801 C yet its ions will readily separate from each other at room temperature when the solid is added to water Explain this by discussing the predominant force that allows an ionic compound to dissolve in water Although the ionic bonds holding a crystal lattice together are strong when the surface of that lattice is in contact with water each ion on that surface will attract the oppositely charged end of water molecules near them That attraction between an ion and a molecule is called an iondipole force These attractive forces soon overcome those existing between the ions themselves and so the crystal structure begins to break down and the ionic compound dissolves As the ions move away from the lattice surface they immediately become surrounded or enclosed in what chemists call a hydration shell Iondipole forces are the primary force responsible for the solubility of ionic compounds in water Na+ Na+ water molecule with dipole iondipole attraction