Checklist for Second Semester Exam
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Chemistry I-Honors Checklist for Second Semester Exam
Chemical Bonding EN & bond type ionic, polar covalent, nonpolar covalent, pure covalent, metallic bonds, single vs. multiple bonds - sigma vs. pi, Octet rule, Lewis structures, formal charge dative or coordinate covalent bonding, resonance, lattice energy of solids
Molecular Geometry VSEPR theory, shapes, bond angles, lone pair vs. bonded pair, exceptions to the Octet Rule, shape with resonance & multiple bonds, polarity of the bonds vs. polarity of the molecule, hybridizations, paramagnetic vs. diamagnetic
Intermolecular Forces ionic, covalent network, metallic, dipole-dipole, hydrogen, van der Waals (London dispersion forces) induced dipoles
Gas Laws Laws & relationships - Boyle, Charles, Gay-Lussac, Amonton, Avogadro, Combined Gas Laws Equation, Ideal Gas Equation & Molecular Wt. determination, Graham’s Law of Effusion, Dalton’s Laws of Partial Pressure Stoichiometry involving gases at STP and non-STP conditions, Ideal vs. Real gases, barometer, units of pressure,standard conditions, manometer
Liquids & Solids M. Pt. & B. Pt - relationship w/ IMF, phase diagram - M. Pt., normal M. Pt., B. Pt., normal B.Pt., triple point, critical point, negative slope of water, names of phase changes phase change problems viscosity, vapor pressure, surface tension, capillary action glass - “supercooled liquid”, amorphous solids
Thermodynamics H, S, & G standard conditions, calorimetry, specific heat of metals heat of formation values, heat of combustion, heat of reactions
Solution Theory “like dissolves like”, solubility of gases vs. Pressure or Temp changes, solubility of solids & temp. changes significance of endo. vs. exothermic dissolution processes, dynamic equilibrium, thermodynamics of the dissolution process colloids & suspensions vs. true solutions saturated vs. unsaturated vs. supersaturated factors that affect solubility, factors that affect the rate of dissolving
Solution Concentrations molality, molarity, normality, percent by mass, mole fraction, solute vs. solvent vs. solution Colligative Properties vapor pressure lowering, freezing point depression, boiling point elevation, osmotic pressure strong vs. weak vs. nonelectrolytes, van’t Hoff factor, Tyndall effect
Gaseous Equilibrium LeChatelier’s Principle -effect of temp. pressure/volume changes, inert gas, catalyst, adding or removing reactants or products, state of matter and effect on value of K, Kc vs. Kp, calc. of Kc or Kp from I.C.E., relationship of kinetics to equilibrium, Law of Mass Action, Q vs. K
Acid-Base Equilibrium + - Kw, pH, pOH, [H ], [OH ] Theories of acids & bases - Arrhenius, Bronsted-Lowry, & Lewis strong vs. weak acids & bases, Ka, Kb, percent dissociation Chemistry I-Honors Second Semester Review Solution Set
1. What is the [OH-1] of an acidic solution if the pH = 2.22? if the pH = 2.22, then pOH = 11.78 , then [OH-1] = 1.7 x 10-12 M
Using the following reaction, answer questions 2 - 11:
2 A(gas) + B(liq) <======> 3 C(gas) + 2 D(solid) H = +110.4 kcal/mole @335 K
2. F Increasing the concentration of C would shift the equilibrium to the right (produce more products).
3. T Increasing the temperature would shift the equilibrium to the right.
4. T Increasing the pressure on the reaction would cause the equilibrium to shift to the left (back to make more reactants). [Note the states of matter!]
5. T A decrease in temperature will alter the value of the equilibrium constant; it would be smaller.
6. F Putting a catalyst into the reaction vessel would not change the value of the equilibrium constant, but it would shift the equilibrium to the right. [Would not cause a shift either.]
7. F Moving the reaction from a 1.0-liter vessel into a 2.0-liter vessel would cause the equilibrium to shift to the left. (Volume increase = pressure decrease)
8. F Removing a small amount of B (still leaving some B at equilibrium) from the reaction would cause the value of Keq to become smaller. [Only temperature changes K]
9. T If 2.0 moles of both reactant A and product C are added to the reaction vessel, no change will occur in the value of K.
10. T Adding 5.0 moles of argon gas (an inert gas) will have no effect on the position of the equilibrium of the reaction.
11. 84.4 For the reaction above, it was determined that, at equilibrium at 25o C, there were 0.600 moles of A, 1.29 moles of B, 4.50 moles of C and 3.00 moles of D. The reaction took place in a 3.00-liter container. What is the KC for the reaction? (Be careful when you set up your equilibrium expression.) A) 5.0; B) 84; C) 589; D) 65; E) 14.2
3 2 3 2 KC = [C] / [A] = [1.50] / [0.200] = 84.4 12. For the reaction: 2 A(g) + 3 B(g) <======> 4 C(g) initially 15.00 moles of A and 12.00 moles of B were placed into a 3.00-liter reaction vessel. Once equilibrium was reached, the number of moles of C was found to be 8.00 moles. What was the equilibrium concentration of B at equilibrium? CAREFUL!
2 A(g) + 3 B(g) <======> 4 C(g) I 15.00 12.00 0.0 [B] = 6.00 mol / 3.00 liter = 2.00 M C -4.00 -6.00 +8.00 E 11.00 6.00 8.00
13. Give the solubility product constant for aluminum chloride if only 0.00255 moles of the compound dissolves in 50.0 liters of water.
+3 - AlCl3 → Al + 3Cl K = [Al][Cl-]3 = (5.10 x 10-5)(1.53 x 10-4)3 = 1.83 x 10-16
o 14. When 16.00 moles of HI are put into a 3.00 liter container and heated to 400 C, it decomposes into H2 gas and I2 vapor until equilibrium is reached. Determine the value of the equilibrium constant, at equilibrium, if HI ionizes 3.50%. You need to write a balanced equation.
2 HI <======> H2 + I2
I 16.00 0.0 0.0
C - 0.0350(16.00) = -0.56 +0.28 +0.28
E 15.44 0.28 0.28
[0.28 mol /3.00 liter]2 -4 KC = ------= 3.3 x 10 [15.44 mol / 3.00 liter ]2
The reaction: 2 A + B <======> C + D (all gases)
I 6.25 3.50 0 0 R -6.00 -3.00 +3.00 +3.00 E 0.25 0.50 3.00 3.00
is studied by placing 6.25 moles of A and 3.50 moles of B in an empty 1.0-liter container. The temperature is kept constant. At equilibrium, 0.50 mole of B remains unreacted. Use this information to answer the next set of questions (#26-28). 15. A What is the number of moles of A that actually reacted? A) 6.0; B) 3.0; C) 10.0; D) 12.0; E) 4.0.
16. C What is the number of moles of C present at equilibrium? A) 6.0; B) 0.50; C) 3.0; D) 2.0; E) 4.0.
17. E What is the value of the equilibrium constant for this system? A) 0.046; B) 0.80; C) 1.0; D) 216; E) 288.
2 2 KC = [3.00] /[0.25] [0.50] = 288 ......
18. It was determined that there were 4.66 x 1011 Pb2+ ions present in 25.00 ml in a saturated solution of lead(II) phosphate. What is the KSP for Pb3(PO4)2?
[Pb+2] = 3x = 4.66 x 1011/6.02 x 1023/ 0.02500 liter = 3.10 x 10-11
+2 3 -3 2 -11 3 -11 2 -53 KSP = [Pb ] [PO4 ] = (3.10 x 10 ) (2.07 x 10 ) = 1.28 x 10
-1 19. What is the geometric shape of OF2? 20 e 2/2 bent
-1 for PCl3? 26 e 3/1 trigonal pyramid
-2 -1 for SeF4 ? 36 e 4/2 square planar
-1 for CH4? 8 e 4/0 tetrahedral
20. What is the molecular weight of a gas if 4.90 grams is contained in a 6.00-liter vessel at 550.0 mm Hg pressure and 220.0oC?
MW = gRT / PV = [(4.90 g)(0.0821)(493 K)] / [(550.0 mm)(1 atm / 760 mm) 6.00 liters]
MW = 45.7 g/mol
21. If the density of propanol is 0.93 g/ml, what is the molality of a solution in which 100.0 grams of sucrose (MW = 342 g/mole) is dissolved in 1800.0 ml of propanol (MW = 60.0 g/mole)?
mass of propanol = 1800.0 ml x 0.93 g /ml = 1674 grams
m = (100.0 g / 342 g/mol ) / 1.76 kg = 0.175 m
22. In a reaction, manganese dioxide (MnO2) changes to give a permanganate ion. Was the substance: A) oxidized; B) reduced; C) neutralized. 23. How many electrons are transferred in the following unbalanced redox reaction? ( 6 electrons )
(+3 e-1)
-1 2- + +3 2 Br + CrO4 + H ------> Br2 + Cr + H2O
(-2 e-1)
24. An aqueous solution boils at 106.2oC when 90.0 grams of an unknown solute is dissolved in 75 ml of o water. What is the molecular weight of the solute? Kb = 0.512 C/m.
o g x kf (90.0 g)( 0.512 C/m) MW = ------= ------= 99.1 g/mol t x kg (6.2oC)(0.075 kg)
25. Which of these molecules would be expected to show a dipole moment (be polar)?
A) SO2; B) CH3F; C) AsF3; D) CCl4; E) OF3. yes yes yes no no
26. Give an example of a material that may be considered to be amorphous. Glass
24 27. Atoms of Mg12 will most readily unite by ionic bonding with atoms of the element having atomic number: A) 18; B) 3; C) 14; D) 13; E) 34 (Se)
28. What is the term for the smallest portion of the crystal lattice that exhibits the pattern of the lattice structure? Ion
+1 +1 29. In the reaction, NH4 + H2O ------> NH3 + H3O , the water molecule serves as: A) a proton donor; B) a proton acceptor; C) a weak base; D) an electrovalent compound.
+1 30. What is the pH of a solution that has a hydronium ion [H3O ]concentration of 0.00340 mole per liter? What would be the pOH of this solution? pH = 2.47; pOH = 11.53
31. How many moles of methane (MW = 16.0 g/mole) are there in a 20.00-liter container if the pressure is 1200.0 mm Hg and the temperature is measured to be -75.0oC?
PV = nRT n = [(1200.0 mm / 760.0)(20.00 liters)] / [(0.0821)(198 K)] = 1.94 moles
32. When a substance can act as either an acid or a base depending on the reaction in which it is involved, the substance is called: A) amphoteric; B) divalent; C) allotrophic; D) covalent; E) isomeric.
33. If an acid is said to be strong, this means: A) it is highly corrosive; B) it is ionized completely in aqueous solution; C) it has a sharp bitter odor; D) it holds together in water as a molecule rather than as ions.
34. Which of the following does not affect the rate of a reaction? A) temperature; B) concentration of the reactants; C) time; D) catalyst; E) nature of reactants.
Give the shape, type of hybridization, and bond angle for the following:
35. xenon tetrachloride 36 e = 4/2 square planar sp3d2 90o
36. ethyne linear sp 180o
37. phosphorus pentachloride 40 e = 5/0 trig bipyramid sp3d 90o & 120o
38. sulfur tetrafluoride 34 e = 4/1 seesaw sp3d 90o & 120o
39. carbonate ion 24 e = 3/0 trig. planar sp2 120o
40. hydrogen sulfide gas 8 e = 2/2 bent sp3 109.5o
41. ammonia gas 8 e = 3/1 trig. pyramid sp3 < 109.5o
42. What is the molal freezing point constant for an organic solvent given the following information: when 4.00 grams of a nonvolatile, nonelectrolyte (MW = 255 g/mole) is added to 150.0 grams of the organic solvent the freezing point of the solution is measured at 34.5oC. The pure solvent freezes at 38.2oC.
o MW = g x kf / t x kg, then kf = MW x t x kg / g = (255 g/mol)(3.7 C)(0.1500 kg) / 4.00 g
o kf = 35 C / m
Classify the following solids: (ionic, covalent network, atomic/molecular, or metallic
43. magnesium chloride ionic
44. ammonia molecular
45. silicon dioxide covalent network
46. methane molecular
47. pure copper metallic
48. glucose molecular 49. What is the molecular weight of an unknown gas is its rate of effusion is 34.5 ml/sec while oxygen's rate of effusion is 25.1 ml/sec?
Rate X 34.5 ml/sec
------= ------= (32.0 g/mol) / X M.WtX = 16.9 g/mol
Rate O2 25.1 ml/sec
Tell what the predominant type of intermolecular force exists between:
50. water and ethyl alcohol hydrogen bonding
51. oil and vinegar van der Waals
52. potssium nitrate dissolved in water ion - dipole
53. hydrogen bromide gas mixed with hydrogen chloride gas dipole - dipole
54. an alloy of brass composed of copper and zinc metallic
======55. What type of hybridization is exhibited by the sulfur trioxide molecule? sp2
56. What type of hybridization exists in the phosphorus trifluoride molecule? sp3
57. If 5.00 liters of gas that is confined in a movable piston at STP has the temperature raised to 500oC and the pressure decreased to 35.0 kPa, what will be the new volume of this gas?
V2 = (V1P1 / T1) x (T2 / P2) = [(5.00 liters)(101.3 kPa) / 273 K] x [773 K / 35.0 kPa]
V2 = 41.0 liters
58. How many kilocalories are released when 25.0 grams of steam, originally at 165oC, is cooled to form liquid water at 35oC?
o o H1 = mCt = (25.0 g)(0.440 cal/g- C)(65 C) = 715 cal
H2 = mH = (25.0 g)(540 cal/g) = 13,500 cal
o o H3 = mCt = (25.0 g)(1.00 cal/g- C)(65 C) = 1625 cal
Htotal = 715 + 13500 + 1625 = 15840 = 15.8 kcal
59. What is the specific heat of a metal given the following information: 166.0 grams of the metal, when dropped into 45.0 grams of distilled water, has its temperature lowered by 45.5o. The water temperature rises by 13.4o
o o o Cmetal = mCt / mt = [(45.0 g)(4.184 J-g C)(13.4 C)] / [(166.0 g)(45.5 C)] o Cmetal = 0.334 J-g C
60. What is the van’t Hoff factor for a 0.885-molal solution of carbonic acid if the freezing point of this aqueous solution is –2.55oC? 2.55 = i(1.86oC/m)(0.885 m) i = 1.55
61. What is the term for the property of colloids that diffracts light? Tyndall effect
62. When 10.0 grams of ice, originally at 0oC, are added to 125.0 grams of water, originally at 92.0oC, what will be the final temperature of the mixture?
H = mHfusion = (10.0 g)(80 cal/g) = 800 cal
o o H = 800 cal = mCt = (125.0 g)(1.00 cal/g- C)(t) = t = 6.4 C o Tfinal of the warm water is now 92.0 - 6.4 = 85.6 C
mCt = mCt o o o (10.0 g)(1.00 cal/g- C)(final - 0) = (125.0 g)(1.00 cal/g- C)(85.6 C - Tfinal) o Tfinal = 79.3 C
63. Based on the phase diagram below, identify the following, using either a point or an arrow: (A) normal boiling point, (B) normal freezing point, (C) critical point, (D) sublimation, (E) deposition, (F) vaporization, (G) melting, (H) triple point, (I) liquefaction, (J) condensation
C
1.0 B A F G
Pressure J (in atm.) 0.50 H
D
E | | | | | | | | 50 100 150 200 250 300 350 400 Temperature (in Kelvin)