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Chemistry - Chap 12 Homework Answers 2014 1. State what the Kinetic-Molecular theory says about the particles of gases in terms of their: a) size small (point masses= has mass but takes up no space) b) motion rapid; random; travel in straight line, collisions are elastic c) energy high energy 2. Compare the density and compressibility of gases versus liquids and solids. solid, liquids = noncompressible. high density. gases = compressible and low density 3. Why is nearly seven times more energy needed to vaporize a given amount of water as to melt it? melting requires overcoming some of the attractive forces because the particles can now slide over one another but are still in contact. Boiling requires overcoming all attractive forces because the particles are freely moving 4. Briefly describe each of the following: a) ionic bonds in ionic compounds- transfer of electrons making ions and att are electrostatic. strong bonds b) covalent bonds in molecular compounds share localized prs of electrons. strong bonds c) metallic bonds in metallic solids.- sea of electrons. mobile nondirectional. strong bonds 5. Describe the following: a) dispersion forces attractions due to instantaneous dipoles. very weak b) dipole-dipole forces- attractions due to permanent dipoles. weak c) hydrogen bonds- att of H of one molecule to O,N,F of another. strongest of these 6. Identify the type of intermolecular forces acting in the liquid state of each of the following substances. a. CH4 disp b. HBr disp, dipole c. NF3 disp, dipole d. H2O disp, H e. Cl2 dispersion 7. What is vapor pressure? On a microscopic basis, how does a vapor pressure develop in a closed flask containing a small amount of liquid? What processes are going on in the flask? pressure exerted by vapor above a liquid. High energy particles at surface escape and exert the pressure 8. Which substance in each pair would be expected to show the largest vapor pressure at a given temperature? The largest vapor pressure means the particles are easy to separate, have low attractive forces: a. H2O (l) or C4H10 (l) only disp while water has disp, dipole, and H bonding. butane’s molecules can separate much easier b. C4H10 (l) or C8H18(l) both have only disp but octane is much larger. same reason as above c. HCl (l) or H2O (l) HCl has disp and dipole but water has all 3. same reasons. d.. Br2 or PH3 bromine has disp whiles PH3 is disp, and dipole so same reason e. H2O or NH3 both have disp, and H bonding. Water can H bond 4 times and 2 l.p. where ammonia has only 1 l.p. For 9-21, choose one of the following terms to match the definition or description given. 9 f 10 I 11 a 12 e 13 h 14 c 15 m 16 g 17 b 18 k 19 20 d 21 j 22. Which of the substances in each of the following sets would be expected to have the highest melting point? Explain why. a. H2, N2, Br2 all disp but bromine largest so most attractions b. H2O, NaCl, He sodium chloride ionic other two are molecular. ionic much higher m.p (memory) c. H2, HCl, H2O hydrogen disp only, HCl disp, and dipole but water all 3. 23.. Classify each of the following solids and describe their properties. a. CaSO4 ionic (has a polyatomic ION). high mp/bp, insulator as solid but conductor as liquid, brittle, low vp b. diamond network. (memory) very high mp.bp, insulator, brittle, very low vp c. Zn metallic.(duh!) high mp/bp, malleable, ductile, conductor, luster, low vp d. glucose, C6H12O6 molecular. low mp/bp, insulator, soft, higher vp e. Xe atomic (but same category as molecular) low mp/bp, insulator, soft, higher vp Chemistry - Chap 12 Homework II Answers 1. Complete the following table. Phase at room temperature = solid, liquid, or gas. Physical properties = brittle, malleable, gas, etc. Compound Type Forces present Phase at r.t. Name Hydrogen Ammonia High or low mp/bp low Low H2 1-NH3 molecular molecular Gas Gas H2O molecular CH3CH2-OH molecular 2-SO2 CO2 3-CaCO3 molecular molecular Ionic dispersion Dispersion, H bonding Dispersion, H bonding Dispersion, H bonding dispersion dispersion Ionic bonds LiClO3 ionic 4-PH3 molecular He CH4 Al(NO3)3 Physical properties at r.t. Soft,insulator Soft,insulator Liquid Water Low Soft,insulator liquid Ethyl alcohol Low Soft,insulator gas gas Solid Sulfur dioxide Carbon dioxide Calcium carbonate Low Low high Ionic bonds solid Lithium chlorate High Gas Gas Gas Solid Phosphorous trihydride Helium Methane Aluminum nitrate Low element molecular ionic Dispersion, dipole-dipole Dispersion Dispersion Ionic bonds Soft,insulator Soft,insulator Brittle, insulator as solid but cond as liquid Brittle, insulator as solid but cond as liquid Soft,insulator Low Low High C4H10 molecular Dispersion Gas Butane Low Soft,insulator Soft,insulator Brittle, insulator as solid but cond as liquid Soft,insulator C Covalent bonds Solid Diamond High Hard, brittle, insulator 5-Fe Network covalent metallic Metallic bond Solid Iron High Mg metallic Metallic bond Solid Magnesium High CCl4 molecular dispersion Gas Low C12H22O11 molecular Dispersion, H Bonding Solid Carbon tetrachloride Sucrose Maleable, ductile, cond, luster Maleable, ductile, cond, luster Soft,insulator Low Soft,insulator 2. Rank items numbered 1,2,3,4 and 5 above from lowest to highest in terms of their a) boiling point/melting point 1,2,4,3 and 5 tie (1,2,4= disp and dip.) (2 larger than 1 & 3 (but barely)) 4 & 5 = high b) vapor pressure. Reverse a answers (remember high attract = high m.p and low v.p) 3. Explain the following data. Compound CH4 only london (dispersion) so low B. P. (oC) -161 Cmpd HBr london and dipole so larger than just B.P. -70 london C2H6 london but larger so higher than above C3H8 london and larger that other two above F2 london and really small Br2 london and big and magic -89 -30 -188 59 HI same as HBr but larger -37 Rank the compounds above from 1-7 for vapor pressure, with 1 being the lowest vapor pressure and 7 the highest. Reverse the b.p.order (same as earlier) 4. Rank the following compounds from lowest to highest for their boiling points: KBr= 4 (highest) H2 =1 (lowest) C6H12O6 = 3 ionic, (rule ) molec; disp only molec; disp, dipole, H bond SO3= 2 molec; disp, dipole 5. Know the definitions for the following terms: ionic solid covalent network solid molecular solid Look them up, lazy intermolecular dipole-dipole attraction dispersion forces cohesion and adhesion viscosity surface tension fluidity boiling point vapor pressure vaporization 6. Naming Practice Magnesium hydroxide ammonium sulfide trisulfur nonoxide sulfur hexafluoride H2SO4 HC2H3O2 HNO3 SnCO3 Cu3(PO4)2 Al2(SO4)3 Fe(C2H3O2)3 Pb(SO3)2 Multiple Choice Ans 1. A 2. C 7. A 8. D 13. B 14. C Mg(OH)2 (NH4)2S S3O9 SF6 sulfuric acid acetic acid nitric acid Tin(II) carbonate Copper(II) phosphate Aluminum sulfate Iron(III)acetate Lead(II) sulfite 3. B 9. A 15. B 4. A 10. A 16. D 5. C 11. D 6. D 12. D