Chem 2A Final Review
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Chem 2A Final Review
------Potentially Useful Information for the Problems Below------4 pKb of dimethylamine = 5.9 10 R=0.0821 (atm L)/(mol K) ------
1. An acidic solution has a pH of 3.43. What is the Hydronium ion concentration?
+ -4 Ans. [H3O ] = 3.7 10
What is the [OH-] concentration? pKw = pH + pOH 14 = 3.43 + pOH pOH=10.57 pOH=-log[OH-] -antilog (pOH)=[OH-] =2.69 10-11
2. What is the pOH of 0.050 M dimethylamine, a weak base?
+ - Me2NH + H2O ⇄ Me2NH2 + OH
+ - Kb = [Me2NH2 ] [OH ] / [Me2NH]
X2 = [(5.9 10-4) (0.050)]-1/2 = 0.0054 pOH = -log(0.0054) = 2.26 pH = 11.73
3.
4.
5. Rank the following from lowest to highest acidity.
1.8 10-5 1.0 10-10 1.2 10-2 8.0 10-9
1 6. In the following reaction what is (are) the base(s) and the acid(s)?
3HCl + Al(OH)3 ⇄ 3H2O + AlCl3
7. In the following reaction what are the initial acid and base
HCl + Mg(OH)2 ⇄ MgCl2 + H2O
8. Determine the number of moles of carbon dioxide produced in the following unbalanced combustion reaction.
C8H17OH + O2 CO2 + H2O
Ans = 8 moles
9. How many grams of NaH2PO4 are needed to react with 0.0106 moles of NaOH in the balanced reaction:
NaH2PO4 + 2NaOH Na3PO4 + 2H2O NaH2PO4 = 119.98 g/mol NaOH = 40.00 g/mol
Ans 0.639
10. In the following balanced reaction 8.00 g of oxygen is used to produce how many grams of HCN?
2NH3(g) + 3O2(g) + 2CH4(g) 2HCN(g) + 6H2O(l) ans 4.51
11. A gas has a volume (in Liters) of 6.00 liters at 27 C with a pressure of 1.0 atm. What is the volume of the gas at 327 C with a pressure of 3.00 atm. Ans. 4.00 12. When 35.6 L of ammonia is reacted with oxygen at 1.0 atm at 25 C, the answer closest to the number of grams of H2O produced in the unbalanced equations is: 4NH3 + 5O2 4NO + 6H2O
PV=nRT n = PV/RT=1 35.6 /0.0821 (25+273) =
13. The answer closest to the number of grams of NaH2PO4 needed to react with 38.74 mL of 0.275 M NaOH, according to the following balanced equation is: (NaH2PO4 = 119.98 g/mol) NaH2PO4 (s) + 2NaOH (aq) Na3POH4 (aq) + 3H2O
2 Ans.0.639
14. In the following reaction identify the compounds that get oxidized and reduced
Al + O2 Al2O3
15. The number of lone pairs of electrons in BrF3 is
+ 16. The molecular arrangement of atoms around H3O is:
Trigonal Pyramidal
17. Polar arrows indicate the polarity of bonds, indicate to which atom the positive side of the arrow would point to for the molecular fragments N-B, N-O, Br-Cl, S-Se respectively.
1. N, O, Cl, S 2. N, N, Cl, Se 3. B, N, Cl, S 4. B, N, Br, Se 5. B, O, Cl, Se
Ans. 4
18. What is the condensed electron configuration for Se
19. The maximum number of electrons an atom with a 1s, 2s, 2p, 3s electron configuration can have is?
20. What is the average atomic mass of iridium based on its two isotopes: 191Ir 190.9609 amu (abundance = 37.120%) and 193Ir 192.9633 amu (abundance = 62.880%) ans. 192.2200
3 21. The amount of heat is required to raise 100.0 g of water from 1.00 C to 99.0C: [heat capacity of water = 1.00 cal/(g C)] is closet to: heat absorbed = specific heat * mass * temp change
9.80 103 cal/(g C)
22. Express 96,342 m using two significant figures
9.60 104 m 9.6 104 m 9.60 10-4 m 9.63 104 m 9.60 104 m
23. The largest volume among the following is
10 nL 10,000 L 1,000 pL 0.01 dL 100 mL
24. The symbol A=37, Z=17, X- (where X stands for the element symbol) represents an ion of chlorine with 20 electrons chlorine with 16 electrons rubidium with 38 electrons rubidium with 36 electrons chlorine with 18 electrons
25. The most likely ionic form of the elements Ca and F is:
Ca2-, F+ Ca2+, F2- Ca2+, F- Ca+, F- Ca+, F2-
26. Convert 233. C to Fahrenheit.
4 451. F 506. F 112. F 130. F 273. F
27. The density of Au is 19.3 g/mL. How many 1-ounce coins could be manufactured from a 1 cubic foot block of gold?
1 ft3 = 0.02832 m3, 1 oz = 28.35 g
1.93 104 3.32 102 2.43 1010 7.30 105 8.21 10-2
28. A metal has a charge of 3+ and 39 electrons. The mass of one of its 7 isotopes is 96 amu and its abundance is 74.8%. Calculate the number of neutrons for this element and what is the element? neutrons = 19, Cl neutrons = 47, Kr neutrons = 54, Kr neutrons = 54, Mo neutrons = 54, Nb
29. A box of dimensions 2.00 inches 3.50 inches 2.500 inches (1 inch = 2.54cm) has a volume closest to
0.2868 L 17.5 L 0.287 L 0.04445 L 0.0444 L
30.. Determine the number of moles of carbon dioxide produced in the following unbalanced combustion reaction.
5 C8H17OH + O2 CO2 + H2O
2 8 6 18 12
31. What is the chemical formula given the following elemental analysis.
168.15g C, 20.16g H, 28.014g N, 32.06g S, 63.99 O
C7H10NSO2 C30H20N2S4O4 C16H2N3S3O6 C16H20N28S32O63 C14H20N2SO4
32. How many grams of NaH2PO4 are needed to react with 38.74 mL of 0.275 M NaOH?
NaH2PO4(s) + NaOH(aq) Na3PO4(aq) + H2O(l)
0.6392 0.2500 1.278 12.00 0.0106
33. In the following unbalanced reaction 8.00 g of oxygen are used to produce 2.14 g of HCN. What is the percent yield of HCN produced?
NH3(g) + O2(g) + CH4(g) HCN(g) + H2O(l)
Ans: 47.6%
6 34. Given that 41.4 g of water reacts with 42.0 g of C3H8, the limiting reactant is
C3H8 + H2O CO + H2
H2O C3H8 CO H2 None of these
35. The volume of 0.100 M Ba(OH)2(aq) solution needed to prepare 6.30 L of 0.003 M Ba(OH)2(aq) solution is
6.3 L 0.189 L 33.3 L 0.03 L 3.0 L
36. The chemical formula for a compound with the empirical formula C7H4O2 and a formula weight of 240.2 g/mol is
C7H4O2 C13H4O5 C21H12O6 C14H8O4 C3.5H2O
37. The formula of Vitamin C is C6H8O6. How many moles of Vitamin C are there in two 500 mg tablet?
1.000 5.68 0.176 2.84 10-3 5.68 10-3
38. The number of chlorine atoms in one mole of aluminum chloride is approximately:
7
3 35.5 6.02 1023 18.06 1023 2.01 1023
39. Potassium nitrate decomposes on heating, producing potassium oxide, gaseous nitrogen and gaseous oxygen. Choose the closest number of grams of KNO3 that must decompose in order to produce 1.35 g of O2 (in the original exam the chemical formula was given…but I want you to write chemical equation for practice).
4.26 6.82 3.41 5.33 0.0338
40. The density of mercury (Hg) is 13.5 g/mL. If a chemist wants to add 2.00 moles of Hg to a reaction vessel, how many milliliters should he add?
401 29.7 7.38 10-4 mL 7.43 14.8
41. If 2.50 moles of H2 reacts with Cl2 to form HCl according to the following unbalanced equation, what number below is closest to the number of moles of HCl produced?
H2(g) + Cl2(g) HCl(g)
1.25 5.00 2.50 3.75 0.625
8 42. Indicate whether the reactants and products are either a Solid (s), Gas (g) or Soluble in Water (aq) in the following double-replacement reactions. a)
2NaOH + Cd(NO3)2 Cd(OH)2 + 2NaNO3
ans. 2NaOH (aq) + Cd(NO3)2(aq) Cd(OH)2(s) + 2NaNO3(aq)
b)
2NaI + PbNO3 2NaNO3 + PbI2
2NaI(aq) + PbNO3(aq) 2NaNO3(aq) + PbI2(s)
43. Using solubility rules to determine which of the following are soluble = Aquous (aq) or insoluble = Solid (s) in water.
Ba(OH)2, BaSO4, BaS, Ba(NO3)2
ans. Ba(OH)2 (aq) , BaSO4 (s) , BaS (s) , Ba(NO3)2 (aq)
44. How many grams of salt (NaCl mw = 58.44 g/mol) are needed to make 65.0 mL of a 0.220 % saline solution?
Ans. (0.220 g NaCl/100 mL solution) 65.0 mL solution = 0.143 g NaCl
45. What is the mass percent in a solution containing 12.1 g of NaCl and 150.1 g water?
Ans. 12.1 g NaCl /(12.1 g NaCl + 150.1 g water) 100 = 7.57 %
9 46. Calculate the number of grams of solute in the following: 50.0 mL of a 12.0 M HNO3 solution
M = mol/L, mol = M L, 50.0 mL 1L/1000mL 12.0 M = 0.600 mol HNO3, mol = g/mw, g = mol mw = 0.600 mol 63.01 g / mol = 37.81 g HNO3
47. Calculate the number of grams of solute in the following: 1.20 L of a 0.0032 M Na2SO4 solution
M = mol/L, mol = M L = 1.20 L 0.0032 M = 0.0038 mol Na2SO4, mol = g /mw, g = mol mw = 0.0038 g/mol 142.04 g/mol = 0.545 g
48. Calculate the molarity of the following: 14.0 g silver Nitrate (AgNO3) in 1.00 L of solution.
Mol = g mw = 14.0 g mol/169.87 g = 0.0824 mol, M = mol/L = 0.0824 / 1.00 L = 0.0824 M
Calculate the molarity of the following: 0.025 mol of potassium chloride (KCl) in 50.0 mL of solution
M = mol/L = 0.025 mol / (50.0 mL 1L/1000mL) = 0.500 M
49. In a dialyzing bag containing colloidal-sized proteins, glucose and NaCl is place in pure water, describe what would happen.
50. Calculate the Osmolarity for: a) 3 M K3PO4
Osmolarity = molarity i = 3 4 = 12 b) 6 M protein
Osmolarity = molarity i = 6 1 = 6 c) what is the Osmolarity by combining the two above examples?
6 + 12 = 18
10 51. Why is the freezing point of a solution of MgCl2 lower then a solution of NaCl?
52. Determine the final concentration of a solution by adding 45 mL of water to 90.0 mL of a 3.0 M NaCl solution.
M1V1=M2V2, M2 = M1V1/V2 = 90 mL 3/45 mL = 6.0 M
53. Determine how many L of water must be added to 34.5 mL of a 12.0 M solution of nitric acid (HNO3) to make a 4.0 M solution.
M1V1= M2V2, V2 = M1V1/M2 = 34.5 mL 12/4 = 103.5 mL = 0.104 L
54. Classify the following reaction as either a combination, decomposition, single replacement, or double displacement reaction.
a) 2NaHCO3 Na2CO3 + CO2 + H2O b) 2Fe + 3Cl2 2FeCl3
55. Which of the following is Not a redox reaction? a) 2CuO 2Cu + O2 b) 2KclO3 2KCl + 3O2 c) CaCO3 CaO + CO2 ans C
56. Determine the oxidation number (oxidation state) of all the elements in the following reactions. a) Mg + 2HCl MgCl2 + H2 b) 2SO2 + O2 2SO3 c) 2Fe2O3 + 3C 4Fe + 3CO2
57. Which species (elements) are oxidized and which are reduced in the following reaction. a) Zn + CuCl2 ZnCl2 + Cu b) 3H2S + 2HNO3 3S + 2NO + 4H2O c) 2FeBr3 2FeBr2 + Br2
11 58. What effect would this have on the rate of a reaction: a) lower the temperature b) increasing the concentration of the reactants c) increasing the concentration of the products d) adding a catalysts
59. What is the correct Eeq for the following reactions: a) 2 NH4ClO4 ⇄ N2 + Cl2 + 2O2 + 4H2O (this is the space shuttle fuel) b) 2C6H6 + 15O2 ⇄ 12CO2 + 6H2O
60. The oxidation number (oxidation state) of sulfur in the following are?
K2SO2, K2S2O3, K2S
61. According to Le Chatelier’s principle what effects will take place on the equilibrium of the following reaction:
CO2 + H2 ⇄ H2O + CO a) Increase [H2] b) Increase [H2O] c) remove H2O and CO
62. Calculate the equilibrium constant for:
N2O4 ⇄ 2NO2
[N2O4] = 0.12 M [2NO2] = 0.55 M ans. = 2.5
63. At equilibrium, in a reaction vessel that is 0.32 L, the following reaction,
CH4 (g) + H2O (g) ⇄ CO (g) + 3H2 (g)
…was found to have an Eeq = 0.26. There are 0.26 mol CO, 0.091 mol H2 and 0.041 mol CH4. What is the concentration of the H2O? (Hint, the vessel is 0.32 L meaning that EACH species has a volume of 0.32L)
12 ans. 0.53 M TOPICS: Lewis Dot Lewis Structure VESPR Class name VESPR Molecular Shape name Polarity Solubility: the phenomena is Likes Dissolve Likes, the fact is molecules dissolve if they have the same solubility Melting and Boiling Points
Mole Amu, Molar Mass Empirical and Molecular Formula
Balancing Chemical Formulas Limiting Reagents Theoretical and Percent Yield
23 64. The answer that is closest to the number of grams of oxygen in 6.022 10 molecules of O2 is: 1) 1.0 4) 64.0 2) 16.0 5) 6.022 1023 3) 32.0
65. Both water and sulfur dioxide are produced from the reaction of sulfuric acid (H2SO4) with copper metal in the following balanced equation. How many moles of H2O will be produced at the same time that 10.0 moles of SO2 is produced? 2H2SO4 + Cu SO2 + 2H2O + CuSO4 1) 5 4) 25 2) 10 5) 30 3) 20
66. Chlorophyll, essential to plants for photosynthesis, contains one magnesium atom, three oxygen atoms, four nitrogen atoms, thirty three carbon atoms and twenty nine hydrogen atoms. What is the chemical formula for chlorophyll? 1) FeO3N4Ca33Hy29 2) Mn3O4N33C29H 3) NaO3Ni4Ca33H29 4) MgO3N4C33H29 5) MnO3N4C33H29
67. Vitamin C (mw = 176.12 g/mol) contains 40.9% C, 4.6% H and 54.5% O. What is the molecular formula of Vitamin C
68. If there are 2.62 1022 atoms in 1.00 g of sodium and they are lined up side by side, what is the length of the line of sodium atoms in miles? Assume that the atoms are spheres of diameter 0.372 nm.
13 69. Mystery element X combines with sulfur to form the compound X4S3 . The molecular mass of X4S3 is 220.09 amu. Mystery element X is: 70. What is the percent yield of sodium carbonate if 1.254 g of sodium hydrogen carbonate (84.01 g/mol) decomposes to give 0.765 g of sodium carbonate (105.99 g/mol)? 2NaHCO3 (s) Na2CO3 (s) + H2O (g) + CO2 (g) 1) 48.4% 2) 96.7% 3) 100% 4) 103% 5) 206%
71. What mass of BaSO4 is produced by starting with 12.1 g of Fe2(SO4)3, in the following balanced reaction?
3BaCl2 (aq) + Fe2(SO4)3 (aq) 3BaSO4 (s) + 2FeCl3 (s) 1) 8.98 10-4 4) 4.03 2) 2.34 5) 21.2 3) 3.03
72. Draw the Lewis dot structure for Barium, Lead, Bismuth, Polonium, and Radon
73. Draw the structure with no double bonds. SOF3- (S is the central atom)
74. Draw a 3-D diagram for each molecule and indicate if the molecule is polar or non-polar. a. OF2 b. PBr3
75. Draw the 3-D structure. Give the VSEPR electron-pair name, the molecular shape name for the following. a. NF3 b. CCl4 + c. CF3
76. Draw and example of hydrogen bonding between NH3 and HF
77. Would you expect the following pairs to be soluble with each other? a. CH4 with H2O
H
H C O H
H
b. with CH2F2
14 15