1. UNIT 17 Review, Part IV Lewis, IMF, Bonding, Acid-Base, Solutions

2. Molecular Compounds:  Are made of nonmetals  Nonmetals have high electronegativity, so they do NOT release their electrons.  Two nonmetals share some of their valence electrons (in bonds) to achieve full octets.  The atoms are CO-valent-ly bonded! LPChem:Wz (after Johannesson) Shared Valence

3. Molecular Geometry  Geometry = shapes  VSEPR Theory  Valence  Shell  Electron  Pair  Repulsion  AKA: electrons hate each other LPChem: Wz Unit 12: Molecular Structure

4. VSEPR Theory  The electrons interacting in molecules (valence shell electron pairs)  Are REPULSED by each other.  The electron pairs around the central atom orient themselves as far apart as possible– in order to minimize their mutual repulsion. Unit 12: Molecular Structure LPChem: Wz

5. I. Lewis Dot Structures  NH 3 LPChem:Wz (after Johannesson) N H H H COO O H H H2OH2O C H H H H  CH 4  CO 2

6. H Cl ++ --

7. ++ --  Assume ALL bonds are polar unless the same element is on both ends!  N 2, O 2, & F 2 are made of nonpolar bonds.  So are N 3 & O 3

8. I. Lewis Dot Structures  NH 3 LPChem:Wz (after Johannesson) N H H H COO O H H H2OH2O C H H H H  CH 4  CO 2 All of these bonds are polar.

9. I. Lewis Dot Structures N3N3 LPChem:Wz (after Johannesson) N N N O O H H H2H2 Cl  Cl 2 O2O2 All of these bonds are nonpolar.

10. The bonds are all polar. Is the MOLECULE Polar?  NH 3 LPChem:Wz (after Johannesson) N H H H COO O H H H2OH2O C H H H H  CH 4  CO 2 POLAR NONPOLAR

11. This ATTRACTION between the molecules is the IMF.

12. The three IMFS: o London Dispersion o Dipole-Dipole o Hydrogen Bonding STRONG weak

13. between temporary dipoles due to uneven e - dispersion All atoms & molecules Weakest strength Stronger for molecules with greater masses. Instantaneous attraction

14. Charge attraction between permanent dipoles All polar molecules Medium strength It is stronger when the molecules are closer.

15. I. Lewis Dot Structures  NH 3 LPChem:Wz (after Johannesson) N H H H COO O H H H2OH2O C H H H H  CH 4  CO 2 POLAR NONPOLAR HIGHER melting points and boiling points (dipole-dipole) LOWER melting points and boiling points (no dipole-dipole)

16. Extreme attraction between molecules with N-H, O-H, or F-H bonds. Molecules with H bound directly to N, O, F Greatest strength Sometimes called a “pseudo bond”, but it is NOT chemical bonding.

17. Which ones exhibit hydrogen bonding?  NH 3 LPChem:Wz (after Johannesson) N H H H COO O H H H2OH2O C H H H H  CH 4  CO 2 H-Bonding! Nope

21. To get to the valence electron on the other side!

26. Nonmetals share because their electronegativities are too high to let any electrons go.

28. POLAR molecules are soluble in (polar) water. NON-polar molecules are insoluble.

29. Metals release their valence electrons because their electronegativities are too low to hold on.

31. Metals release their valence electrons because their electronegativities are too low to hold on to them.

32. STRONGEST WEAKEST

33. C. Johannesson ACID-BASE  electrolytes  turn litmus red  sour taste  react with metals to form H 2 gas  slippery to touch  turn litmus blue  bitter taste ChemASAP  vinegar, milk, soda, apples, citrus fruits  ammonia, lye, antacid, baking soda

34. C. Johannesson ACID-BASE  High H + (H 3 O + ) conc.  High OH - conc.  turn litmus red  Low pH (<7)  Formula: begins with H ends with a NM  Formula (usually): begins with a M Ends with OH  turn litmus blue  High pH (>7) ChemASAP

35. C. Johannesson B. Definitions AcidsAcids release hydrogen ions (H + ) AcidsAcids create hydronium ions (H 3 O + ) H HHHH H Cl OO – + acid hydronium

36. C. Johannesson B. Definitions BasesBases form hydroxide ions (OH - ) H H H H H H N NO O – + H H H H base hydroxide

37. LPChem:Wz B. pH Calculations pH pOH [H + ] (H 3 O + ) [OH - ] -log[H 3 O + ]-log[OH - ] 10^ (–pH) 10^ (–pOH) K w = [H 3 O + ][OH - ] 14 = pH + pOH

38. _  2 sig figs C. Johannesson B. pH Scale  What is the pH of 0.010 M HNO 3 ? pH = -log[H 3 O + ] pH = -log[0.010] pH = 2.00 Acidic or basic? Acidic __  2 sig figs after the decimal strong acid         pH < 7

39. LPChem:Wz B. pH Scale  What is the [H 3 O + ] of a solution with pH = 7.45?  pH = -log[H 3 O + ]  Therefore 10^ -pH = [H 3 O + ]  10^ -7.45 = [H 3 O + ]  = 3.6 x 10 -8 M

40. LPChem:Wz A. Neutralization  Chemical reaction between an acid and a base.

41. LPChem:Wz A. Neutralization  Chemical reaction between an acid and a base.  Products are a salt (ionic compound) and water.

42. A. Neutralization ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H 2 O Acid + Base = Salt + Water is a neutralization reaction. Titration is used to solve for an unknown concentration in acid-base neutralizations.

43. C. Johannesson B. Titration moles H 3 O + = moles OH - M  V  n = M  V  n M:Molarity V:volume n:# of H + ions in the acid or OH - ions in the base

44. LPChem:Wz B. Titration  10.0 mL of 2.3M LiOH are required to neutralize 20.0 mL of HNO 2. Find the molarity of HNO 2. H3O+H3O+ M = ? V = 20.0 mL n = 1 OH - M = 2.3M V = 10.0 mL n = 1 MV# = MV# (2.3M)(10.0mL)(1) = M(20.0mL)(1) M = 1.15M HNO 2

45. C. Johannesson A. Definitions  Solution -  Solution - homogeneous mixture Solvent Solvent – the dissolver (present in greater amount) Solute Solute - substance being dissolved

46. LPChem:Wz B. Solvation Strong Electrolyte Non- Electrolyte Ionic compounds, Strong acids, Strong bases Molecular substances Weak Electrolyte Weak acids & Weak bases i =1 1 < i < 2 i =2 or more

47. C. Johannesson B. Solvation NONPOLAR POLAR “Like Dissolves Like”

48. C. Johannesson C. Solubility SATURATED SOLUTION no more solute can dissolve UNSATURATED SOLUTION more solute can dissolve SUPERSATURATED SOLUTION Unstable. crystals form if solute is added concentration

49. C. Johannesson A. Definition  Colligative Property property that depends on the concentration of solute particles, not their identity

50. B. Types  Freezing Point Depression  Freezing Point Depression (  T f ) f.p. of a solution is lower than f.p. of the pure solvent  Boiling Point Elevation  Boiling Point Elevation (  T b ) b.p. of a solution is higher than b.p. of the pure solvent T b(normal) +  T b = T b(elevated) T f(normal) -  T f = T f(depressed) LPChem:Wz

51. C. Johannesson C. Calculations  T : change in temperature (° C ) K :constant based on the solvent (° C·kg/mol ) m :molality ( m ) i :ion number (# of particles)  T = K · m · i