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American Chemical Society General Chemistry

Atomic structure, stoichiometry, bonding, solutions, equilibrium, and electrochemistry.

These questions are original. This is not an official American Chemical Society exam, and FreeExam is not affiliated with the American Chemical Society.

  1. 1.A neutral sodium atom has atomic number 11 and mass number 23. How many neutrons are in its nucleus?

  2. 2.An ion has 17 protons, 18 neutrons, and 18 electrons. Which description of that ion is correct?

  3. 3.Two neutral atoms each have 6 protons. One has 6 neutrons and the other has 8 neutrons. Which statement is correct?

  4. 4.Which particle has a charge of 1- and a mass much smaller than the mass of a proton?

  5. 5.In a gold-foil experiment, most alpha particles pass through the foil and a few bounce back. Which picture of the atom fits that result?

  6. 6.A chlorine sample contains 75.0 percent chlorine-35 atoms and 25.0 percent chlorine-37 atoms. What is the average atomic mass?

  7. 7.How many protons, neutrons, and electrons are in 40Ca2+? The atomic number of calcium is 20.

  8. 8.Which statement about the mass number of an atom is correct?

  9. 9.What is the ground-state electron configuration of a neutral oxygen atom? Oxygen has atomic number 8.

  10. 10.Which configuration is the ground state of a neutral sodium atom? Sodium has atomic number 11.

  11. 11.Ground-state nitrogen has the configuration 1s2 2s2 2p3. How many unpaired electrons does that atom have?

  12. 12.Which species has the ground-state configuration 1s2 2s2 2p6?

  13. 13.What is the noble-gas shorthand for ground-state calcium? Calcium has atomic number 20.

  14. 14.Chromium has atomic number 24 and an exceptional ground state. Which configuration is correct?

  15. 15.Copper has atomic number 29 and an exceptional ground state. Which configuration is correct?

  16. 16.Neutral iron is [Ar] 4s2 3d6. Which configuration matches Fe3+?

  17. 17.Which set of quantum numbers is allowed for an electron?

  18. 18.How many orbitals are in a 3p subshell, and how many electrons can that subshell hold?

  19. 19.Which atom has the largest atomic radius?

  20. 20.Which element has the highest first ionization energy?

  21. 21.Why does atomic radius increase from lithium down Group 1 to cesium?

  22. 22.Which order of electronegativity is correct for fluorine, chlorine, and bromine?

  23. 23.Na+ and F- each have 10 electrons. Which comparison is correct?

  24. 24.A chlorine atom gains one electron and becomes Cl-. How does the radius change?

  25. 25.Which element is a halogen?

  26. 26.Which comparison of oxygen and sulfur is correct?

  27. 27.The first four ionization energies of an element, in kJ/mol, are 580, 1820, 2750, and 11600. What does the jump after the third electron indicate?

  28. 28.Which statement about metals on the periodic table is correct?

  29. 29.Methane, CH4, has four bonding pairs and no lone pairs on carbon. What is its molecular shape?

  30. 30.A water molecule has two bonding pairs and two lone pairs on oxygen. What is the molecular shape?

  31. 31.Ammonia has three bonding pairs and one lone pair on nitrogen. What is the molecular shape?

  32. 32.Carbon dioxide has two double bonds and no lone pairs on the carbon atom. Which description fits CO2?

  33. 33.Boron trifluoride has three bonding pairs and no lone pair on boron. What is its molecular shape?

  34. 34.Which substance is ionic?

  35. 35.Water boils far higher than hydrogen sulfide, H2S. Which attraction best explains that difference?

  36. 36.Which bond is the most polar?

  37. 37.Which statement describes the bond that holds the two atoms together in one H2 molecule?

  38. 38.Which description matches London dispersion forces?

  39. 39.How many moles of water are in 36.0 g of H2O? Use 18.0 g/mol.

  40. 40.What mass of O2 contains 2.00 mol of oxygen molecules? Use 32.0 g/mol.

  41. 41.The equation is 2 H2 + O2 -> 2 H2O. If 4.00 mol of H2 reacts with excess O2, how many moles of water form?

  42. 42.Carbon burns by C + O2 -> CO2. What mass of CO2 forms from 2.00 mol of carbon when oxygen is excess? Use 44.0 g/mol for CO2.

  43. 43.A synthesis has a theoretical yield of 20.0 g. The isolated product has a mass of 15.0 g. What is the percent yield?

  44. 44.For 2 H2 + O2 -> 2 H2O, a flask contains 4.00 mol of H2 and 1.00 mol of O2. Which statement is correct?

  45. 45.What mass of water can form from 10.0 g of H2 and 64.0 g of O2 by 2 H2 + O2 -> 2 H2O? Use 2.00 g/mol for H2, 32.0 g/mol for O2, and 18.0 g/mol for water.

  46. 46.A compound is 75.0 percent carbon and 25.0 percent hydrogen by mass. What is its empirical formula? Use 12.0 g/mol for C and 1.00 g/mol for H.

  47. 47.Propane burns by C3H8 + 5 O2 -> 3 CO2 + 4 H2O. How many moles of CO2 form when 4.00 mol of C3H8 burns in excess oxygen?

  48. 48.Using C3H8 + 5 O2 -> 3 CO2 + 4 H2O, what mass of O2 is required to burn 2.00 mol of propane? Use 32.0 g/mol for O2.

  49. 49.The smallest whole-number equation for aluminum burning in oxygen is 4 Al + ? O2 -> 2 Al2O3. What belongs in front of O2?

  50. 50.A 4.00 g sample of CaCO3 decomposes completely by CaCO3 -> CaO + CO2. What mass of CO2 forms? Use 100.0 g/mol for CaCO3 and 44.0 g/mol for CO2.

  51. 51.How many grams of NaCl are needed to prepare 0.250 L of 0.400 M NaCl? Use 58.5 g/mol.

  52. 52.Excess zinc is added to 0.200 mol of HCl. The equation is Zn + 2 HCl -> ZnCl2 + H2. How many moles of H2 can form?

  53. 53.What volume does 1.00 mol of an ideal gas occupy at 1.00 atm and 300. K? Use R = 0.0821 L atm / mol K.

  54. 54.An ideal gas has P = 2.00 atm, n = 1.00 mol, and T = 300. K. What is its volume? Use R = 0.0821 L atm / mol K.

  55. 55.A gas sample occupies 2.00 L at 300. K. The pressure stays constant while the temperature becomes 600. K. What is the new volume?

  56. 56.A gas occupies 3.00 L at 2.00 atm. Temperature stays constant and the pressure becomes 1.00 atm. What is the new volume?

  57. 57.A rigid flask holds a gas at 1.50 atm and 300. K. The gas is heated to 600. K, and the amount of gas stays the same. What is the new pressure?

  58. 58.An ideal gas starts at 1.00 atm, 2.00 L, and 300. K. It is changed to 2.00 atm and 600. K. What is the new volume?

  59. 59.A mixture contains 0.250 mol of N2 and 0.750 mol of O2 at a total pressure of 2.00 atm. What is the partial pressure of N2? Treat both gases as ideal.

  60. 60.What is the density of O2 gas at 1.00 atm and 300. K? Use 32.0 g/mol and R = 0.0821 L atm / mol K.

  61. 61.A gas has a density of 1.79 g/L at 1.00 atm and 300. K. What is its molar mass? Use R = 0.0821 L atm / mol K.

  62. 62.A 2.00 L vessel at 300. K contains an ideal gas at 1.00 atm. How many moles of gas are in the vessel? Use R = 0.0821 L atm / mol K.

  63. 63.How much heat is required to raise the temperature of 100.0 g of liquid water by 10.0 degrees Celsius? Use c = 4.18 J/g degree Celsius.

  64. 64.A reaction releases 200. kJ when 2.00 mol of a reactant is consumed. What is the enthalpy change per mole of that reactant?

  65. 65.In a coffee-cup calorimeter, 50.0 g of water warms by 4.00 degrees Celsius. How much heat did the water absorb? Use c = 4.18 J/g degree Celsius and ignore the cup.

  66. 66.One thermochemical step has delta H = -200. kJ. A second step, added to reach the target reaction, has delta H = +50. kJ. What is delta H for the target?

  67. 67.Which process is exothermic?

  68. 68.The standard enthalpy of combustion of a fuel is -800. kJ/mol. How much heat is released when 0.250 mol of the fuel burns completely?

  69. 69.A metal has specific heat 0.450 J/g degree Celsius. A 20.0 g sample cools from 80.0 degrees Celsius to 30.0 degrees Celsius. How much heat does the metal release?

  70. 70.A reaction is carried out at constant pressure. Which statement about its enthalpy change is correct?

  71. 71.Breaking the bonds in the reactants of a gas-phase reaction requires 600. kJ, and forming the bonds in the products releases 750. kJ. Estimate delta H.

  72. 72.A 25.0 g metal sample at 100.0 degrees Celsius is placed in 100.0 g of water at 20.0 degrees Celsius. Both reach 22.0 degrees Celsius, and the calorimeter loses no heat. What did the water gain? Use c = 4.18 J/g degree Celsius for water.

  73. 73.A solution contains 0.500 mol of solute in 0.250 L of solution. What is its molarity?

  74. 74.A student dilutes 50.0 mL of 2.00 M HCl with water until the solution volume is 250.0 mL. What is the new molarity?

  75. 75.Which mixture is a solution?

  76. 76.A mixture is prepared from 5.00 g of NaCl and 95.0 g of water. What is the mass percent of NaCl in the mixture?

  77. 77.What mass of KCl is needed to prepare 0.500 L of 0.200 M KCl? Use 74.6 g/mol.

  78. 78.Which dissolved substance behaves as a strong electrolyte?

  79. 79.Concentrated hydrochloric acid is 12.0 M. What volume of this acid contains 0.300 mol of HCl?

  80. 80.Which solute should dissolve best in liquid water?

  81. 81.A chemist adds a catalyst to a reaction mixture. Which effect does that catalyst have?

  82. 82.A reaction is first order in reactant A. Temperature is constant, and the concentration of A is doubled. What happens to the initial rate?

  83. 83.A reaction is warmed, and its rate increases. Which explanation fits the usual effect of temperature?

  84. 84.A measured rate law is rate = k[NO]^2[Cl2]. What is the overall order of the reaction?

  85. 85.A first-order decay has a half-life of 20.0 minutes. If 8.00 g is present at the start, how much remains after 60.0 minutes?

  86. 86.Which statement about an experimental rate law is correct?

  87. 87.For the equilibrium aA + bB <=> cC + dD, which expression is the concentration equilibrium constant Kc?

  88. 88.The equilibrium N2(g) + 3 H2(g) <=> 2 NH3(g) is disturbed by adding more H2 at constant volume and temperature. Which change occurs?

  89. 89.The volume of an equilibrium mixture of N2(g), H2(g), and NH3(g) is decreased at constant temperature. The equation is N2 + 3 H2 <=> 2 NH3. Which way does the system shift?

  90. 90.A reversible reaction gives off heat in the forward direction. The equilibrium mixture is heated at constant volume. What happens?

  91. 91.For a reaction at a stated temperature, Kc = 4.0 x 10^6. Which conclusion is justified?

  92. 92.A catalyst is added to a mixture that is already at equilibrium. What is the expected result?

  93. 93.At 25 degrees Celsius, a solution has [H+] = 1.0 x 10^-3 M. What is its pH?

  94. 94.A solution has pH 2.00. What is its hydrogen-ion concentration?

  95. 95.What is the pH of 0.010 M HCl at 25 degrees Celsius if the acid dissociates completely?

  96. 96.At 25 degrees Celsius, [OH-] = 1.0 x 10^-3 M and Kw = 1.0 x 10^-14. What is the pH?

  97. 97.A weak acid HA is initially 0.10 M. At equilibrium [H+] = 1.0 x 10^-3 M, and that amount is small beside 0.10 M. What is Ka?

  98. 98.Which statement about a Bronsted-Lowry acid-base pair is correct?

  99. 99.In the half-reaction Zn(s) -> Zn2+(aq) + 2 e-, what happens to zinc?

  100. 100.In the half-reaction Cu2+ + 2 e- -> Cu, what happens to Cu2+?

  101. 101.Using the rules that H is +1 and O is -2 in H2SO4, what is the oxidation number of sulfur?

  102. 102.In a galvanic cell, which statement about the electrode where oxidation occurs is correct?

  103. 103.In a galvanic cell, which path do the electrons take through the external wire?

  104. 104.A galvanic cell oxidizes Zn and reduces Cu2+. The standard reduction potential is +0.34 V for Cu2+/Cu and -0.76 V for Zn2+/Zn. What is E degree cell?

  105. 105.A redox reaction has a standard cell potential of +1.10 V. What does that positive value mean?

  106. 106.Which description of electrolysis is correct?

  107. 107.A radioactive sample contains 80.0 mg of an isotope with a half-life of 2.0 hours. How much of that isotope remains after 6.0 hours?

  108. 108.Which description of nuclear radiation is correct?