Final Practice Test Solutions - WordPress.com · Final Practice Test Solutions 1. In a...
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Final Practice Test Solutions
1. In a double-displacement reaction, hydrogen chloride and sodium hydroxide react to produce sodium chloride. Another product is
a. water. c. hydrogen gas.
b. potassium chloride. d. sodium hydride.
• HCl + NaOH NaCl + H2O
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2. The number of atoms in 1 mol of carbon is
a. 5.022 x 1022. c. 6.022 x 1023.
b. 6.022 x 1022. d. 5.022 x 1023.
• 1 mole of anything Avogadro’s number = 6.022 x 1023
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3. A prospector finds 39.39 g of pure gold (atomic mass 196.9665 amu). She has
a. 1.204 x 1023 atoms of Au. c. 2.308 x 1023 atoms of Au.
b. 6.022 x 1023 atoms of Au. d. 4.306 x 1023 atoms of Au.
• 39.29 g Au moles Au atoms Au
• 39.29 g Au x 1 moles Au = 0.2 moles Au196.96 g Au
• 0.2 moles Au x 6.022 x 1023 atoms = 1.2 x 1023 atoms Au1 mole
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4. The equation AX A + X is the general equation for a
a. decomposition reaction. c. single-displacement reaction.
b. synthesis reaction. d. combustion reaction.
• Decomposition - AX A + X
• Synthesis – A + X AX
• Single – AX + B AB + X
• Double – AX + BY AY + BX
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5. How many moles of atoms are in 50.15 g of mercury (atomic mass 200.59 amu)?
a. 0.2500 mol c. 0.1001 mol
b. 0.1504 mol d. 0.4000 mol
• Grams moles
• 50.15 g Hg x 1 mole Hg = 0.25 mole Hg200.59 g Hg
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6. The equation 2C2H7OH + 9O 6CO2 + 8H2O is an example of which type of reaction?
a. single-replacement reaction
b. double-replacement reaction
c. combustion reaction
d. decomposition reaction
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7. When the equation Fe3O4 + Al Al2O3 + Fe is correctly balanced, what is the coefficient of Fe?
a. 9 c. 6
b. 4 d. 3
• 3Fe3O4 + 8Al 4Al2O3 + 9Fe
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8. How many liters of hydrogen gas (H2) are needed to react with CS2 to produce 2.50 L of CH4 at STP?
4H2 + CS2 CH4 + 2H2S
a. 7.50 L c. 10.0 L
b. 2.50 L d. 5.00 L
• 4H2 + CS2 CH4 + 2H2S
• 2.50 L CH4 x 4 L H2 = 10 L H2
1 L CH4
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9. For the reaction represented by the equation
SO3 + H2O H2SO4
how many grams of sulfuric acid can be produced from 200. g of sulfur trioxide and 100. g of water?
a. 200. g c. 100. g
b. 245 g d. 285 g
• 200 g SO3 g H2SO4
• 200 g SO3 x 1 mol SO3 x 1 mol H2SO4 x 98 g H2SO4 = 245 g H2SO4
80 g SO3 1 mol SO3 1 mol
• 100 g H2Ox1 mol H2O x1 mol H2SO4 x 98 g H2SO4 = 544 g H2SO4
18 g H2O 1 mol H2O 1 mol
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10. Calculate the approximate volume of a 0.600 mol sample of gas at 15.0°C and a pressure of 1.10 atm.
a. 139 L c. 12.9 L
b. 22.4 L d. 24.6 L
• PV = nRT
• P = 1.10 atm
• V = ?
• N = 0.600 mol
• R = 0.0821
• T = 15 C + 273.15 = 288.15 K
• (1.10)V = (0.6)(0.0821)(288.15)
• V = 12.9 L
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11. What is the volume, in liters, of 0.500 mol of C3H8 gas at STP?
a. 11.2 L c. 22.4 L
b. 16.8 L d. 0.0335 L
• PV = nRT
• P = 1 atm (at STP)
• V = ?
• N = 0.500 mol
• R = 0.0821
• T = 0 C + 273.15 = 273.15 K
• (1)V = (0.5)(0.0821)(273.15)
• V = 11.2 L
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12. Which coefficients correctly balance the formula?
NH4NO2 N2 + H2O
a. 1,2,2 c. 1,1,2
b. 2,1,1 d. 2,2,2
• 1NH4NO2 1N2 + 2H2O
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13. For the reaction represented by the equation
N2 + 3H2 2NH3
how many moles of nitrogen are required to produce 18 mol of ammonia?
a. 18 mol c. 9.0 mol
b. 27 mol d. 36 mol
• 18 mol NH3 x 1 mol N2 = 9 mol N2
2 mol NH3
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14. For the reaction represented by the equation
2Na + Cl2 2NaCl
how many grams of chlorine gas are required to react completely with 2.00 mol of sodium?
a. 35.5 g c. 141.8 g
b. 70.9 g d. 212.7 g
• 2 mol Na x 1 mol Cl2 x 70.9 g Cl2 = 70.9 g Cl2
2 mol Na 1 mol Cl2
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15. How many moles of aluminum are needed to react completely with 1.2 mol of FeO?
2Al(s) + 3FeO(s) 3Fe(s) + Al2O (s)
a. 2.4 mol c. 1.2 mol
b. 0.8 mol d. 1.6 mol
• 1.2 mol FeO x 2 mol Al = 0.8 mol Al 3 mol FeO
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16. How many grams of chromium are needed to react with an excess of CuSO to produce 27.0 g Cu?
2Cr + 3CuSO4 Cr2(SO4)3 + 3Cu
a. 18.0 g c. 33.2 g
b. 14.7 g d. 81.5 g
• 27 g Cu mol Cu mol Cr g Cr
• 27 g Cu x 1 mol Cu x 2 mol Cr x 52 g Cr = 14.7 g Cr 63.5 g Cu 3 mol Cu 1 mol Cr
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17. What is the molarity of a solution that contains 0.202 mol KClin 7.98 L solution?
a. 0.459 M c. 1.363 M
b. 0.0132 M d. 0.0253 M
• Molarity = moles volume (L)
• M = 0.202 = 0.0267.58 L
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18. What is the molarity of a solution that contains 125 g NaCl in 4.00 L solution?
a. 0.535 M c. 31.3 M
b. 2.14 M d. 8.56 M
• Molarity = moles volume (L)
• Volume = 4.00 L
• Moles = ? use grams and convert to moles
• 125 g NaCl x 1 mol NaCl = 2.14 mol NaCl58.5 g NaCl
• 2.14 mol = 0.53 M NaCl4.00 L
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19. How many mL of a 2.0M NaBr solution are needed to make 200.0 mL of 0.50M NaBr?
a. 100 mL c. 25 mL
b. 150 mL d. 50 mL
• M1V1 = M2V2
• M1 = 2.0 M
• V1 = ?
• M2 = 0.50 M
• V2 = 200 mL (no need to convert to Liters)
• (2.0) V1 = (0.50)(200)
• V1 = (0.50)(200)(2.0)
• V1 = 50 mL
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20. For a process in which ∆H is –298 kJ and ∆S is 100 J/k, calculate the change in the free energy at 0°C.
a. –325 kJ c. –198 kJ
b. –298 kJ d. –271 kJ
• ∆G = ∆H - T∆S
• ∆H = -298 kJ
• ∆S = 100 J Convert to kJ 100/1000 = 0.1 kJ
• T = 0 C Convert to K 0 + 273.15 = 273.15 K
• ∆G = (-298) – (273)(0.1)
• ∆G = -325 kJ
• ∆G = free energy
• ∆H = enthalpy (heat)
• ∆S = entropy (disorder)
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21. Which expression defines the change in free energy?
a. ∆H + T∆G c. ∆S – T∆H
b. ∆H + T∆S d. ∆H – T∆S
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22. Spontaneous reactions are driven by
a. decreasing enthalpy and decreasing entropy.
b. decreasing enthalpy and increasing entropy.
c. increasing enthalpy and increasing entropy.
d. increasing enthalpy and decreasing entropy.
• Spontaneous reactions Low ∆H and high ∆S
• Non-spontaneous reactions High ∆H and low ∆S
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23. How much energy does a copper sample absorb as energy in the form of heat if its specific heat is 0.384 J/(g•°C), its mass is 8.00 g, and it is heated from 10.0°C to 40.0°C?
a. 0.0016 J c. 92.2 J
b. 92.2 J/(g•°C) d. 0.0016 J/(g•°C)
• Q = mc∆T
• M = 8.00 g
• C = 0.384 J/(gC)
• ∆T = Tfinal – Tinitial = 40-10 = 30 C
• Q = (8)(0.384)(30) = 92.2 J
Unit for specific heat!
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24. The standard molar enthalpy of vaporization for water is 40.79 kJ/mol. What mass of steam is required to release 500. kJ of energy upon condensation? (Molar mass of water is 18.02 g/mol.)
a. 221 g c. 325 g
b. 1130 g d. 1660 g
• Q = Hv m
• Q = 500 kJ
• Hv = 40.79 kJ/mol
• M = moles (see unit above?)
• 500 kJ = (40.79 kJ/mol)m
• 500 = m = 12.26 moles40.79
• 12.26 moles H2O x 18 g H2O = 220.6 g H2O 1 mol H2O
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25. In the reaction represented by the equation
HClO3 + NH3 NH4+ + ClO3
-
, the conjugate base of HClO3 is
a. not shown. c. NH3.
b. NH4+ d. ClO3
-
• Conjugate acid-base pairs • HClO3 and ClO3
-
• NH3 and NH4+
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26. The pH of a solution is 9.0. What is its H3O+ concentration?
a. 1 x 10-9 M c. 1 x 10-7 M
b. 1 x 10-5 M d. 9 M
• [H3O+]= [H+]
• pH = -log[H+]
• [H+] = 10-pH
• [H+] = 10-9 = 1 x 10-9
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27. What is the pH of a 10–5 M KOH solution?
a. 11 c. 3
b. 9 d. 5
• KOH = base 10-5 = [OH-]
• Kw = [H+] x [OH-]
• Kw = [H+][OH-]
• 1 x 10-14 = 10-9
10-5
• pH = -log[H+]
• -log[10-9] = 9
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28. What is the molarity of an HCl solution if 125 mL is neutralized in a titration by 76.0 mL of 1.22 M KOH?
a. 0.455 M c. 0.371 M
b. 0.617 M d. 0.742 M
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29. What are the Brønsted-Lowry acids in the following equilibrium reaction?
CN + H O HCN + OH
a. CN-, H2O c. H2O, OH-
b. CN-, OH- d. H2O, HCN
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30. Which of the following is the correctly balanced equation for the incomplete combustion of heptene, C7H14?
a. C7H14 + O2 + C7O2 + 7H2 c. 2C7H14 + 21O2 + 14CO + 14H2O
b. C7H14 + 14O + 7CO + 7H2O d. C7H14 + 7O2 + 7CO + 7H2O
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31. How many atoms are in 0.075 mol of titanium?
a. 1.2 x 10-25 c. 2.2 x 1024
b. 6.4 x 102 d. 4.5 x 1022
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32. In the equation 2KClO3 2KCl + 3O2, how many moles of oxygen are produced when 3.0 mol of KClO3 decompose completely?
a. 4.5 mol c. 1.0 mol
b. 3.0 mol d. 2.5 mol
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33. For the reaction represented by the equation 2Fe + O2 2FeO, how many grams of iron(II) oxide are produced from 8.00 mol of iron in an excess of oxygen?
a. 1310 g c. 712 g
b. 71.8 g d. 575 g
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1. A
2. C
3. A
4. A
5. A
6. C
7. A
8. C
9. B
10. C
11. A
12. C
13. C
14. B
15. B
16. B
17. D
18. A
19. D
20. A
21. D
22. B
23. C
24. A
25. D
26. A
27. B
28. D
29. D
30. D
31. D
32. A
33. D