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American Chemical Society General Chemistry Stoichiometry

The mole, formulas, limiting reactants, yields, and gas volumes.

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 sample of carbon dioxide has a mass of 88.0 g. The molar mass of CO2 is 44.0 g/mol. How many moles of CO2 are in the sample?

  2. 2.Find the mass of 3.00 mol of water. The molar mass of H2O is 18.0 g/mol.

  3. 3.Sodium hydroxide pellets have a combined mass of 80.0 g. The molar mass of NaOH is 40.0 g/mol. How many moles of NaOH is that?

  4. 4.A chemist needs 0.500 mol of calcium carbonate. The molar mass of CaCO3 is 100 g/mol. What mass should be weighed?

  5. 5.Methane in a sealed bulb has a mass of 16.0 g. The molar mass of CH4 is 16.0 g/mol. How many moles of methane are present?

  6. 6.Calculate the mass of 4.00 mol of ammonia. The molar mass of NH3 is 17.0 g/mol.

  7. 7.An acid bottle contains 49.0 g of sulfuric acid. The molar mass of H2SO4 is 98.0 g/mol. How many moles of H2SO4 are in the bottle?

  8. 8.A cylinder delivers 2.50 mol of oxygen gas. The molar mass of O2 is 32.0 g/mol. What is the mass of that oxygen?

  9. 9.A beaker holds 180 g of glucose, C6H12O6. The molar mass of C6H12O6 is 180 g/mol. How many moles of glucose are in the beaker?

  10. 10.How many molecules are in 2.00 mol of nitrogen gas, N2? Use 6.022 × 10^23 per mole.

  11. 11.A storage tank holds 3.011 × 10^23 molecules of carbon dioxide. Use 6.022 × 10^23 per mole. How many moles of CO2 is that?

  12. 12.How many atoms are in 1.00 mol of water? Each H2O molecule has 3 atoms. Use 6.022 × 10^23 per mole.

  13. 13.A flask contains 0.250 mol of O2 molecules. Use 6.022 × 10^23 per mole. How many oxygen molecules are in the flask?

  14. 14.An iron wire contains 1.2044 × 10^24 Fe atoms. Use 6.022 × 10^23 per mole. How many moles of iron atoms is that?

  15. 15.How many oxygen atoms are in 0.500 mol of CO2? Each molecule has 2 oxygen atoms. Use 6.022 × 10^23 per mole.

  16. 16.Count the molecules in 5.00 mol of hydrogen chloride, HCl. Use 6.022 × 10^23 per mole.

  17. 17.A sample of ammonia contains 1.8066 × 10^24 molecules. Use 6.022 × 10^23 per mole. How many moles of NH3 are present?

  18. 18.Phosphorus vapor is P4. How many atoms are in 0.100 mol of P4? Each molecule has 4 atoms. Use 6.022 × 10^23 per mole.

  19. 19.A sample contains 36.0 g C and 6.0 g H. Atomic masses: C 12.0, H 1.0. The molar mass is 42.0 g/mol. What is the molecular formula?

  20. 20.A hydrocarbon is 80.0% C and 20.0% H by mass. Atomic masses: C 12.0, H 1.0. The molar mass is 30.0 g/mol. What is the molecular formula?

  21. 21.Combustion leaves a compound analysis of 24.0 g C, 4.0 g H, and 32.0 g O. Atomic masses: C 12.0, H 1.0, O 16.0. The molar mass is 60.0 g/mol. What is the molecular formula?

  22. 22.A mineral is 40.0% Ca, 12.0% C, and 48.0% O by mass. Atomic masses: Ca 40.0, C 12.0, O 16.0. The molar mass is 100 g/mol. What is the molecular formula?

  23. 23.An alkene sample contains 60.0 g C and 10.0 g H. Atomic masses: C 12.0, H 1.0. The molar mass is 70.0 g/mol. What is the molecular formula?

  24. 24.A nitrogen hydride is 87.5% N and 12.5% H by mass. Atomic masses: N 14.0, H 1.0. The molar mass is 32.0 g/mol. What is the molecular formula?

  25. 25.An oxide sample contains 28.0 g N and 64.0 g O. Atomic masses: N 14.0, O 16.0. The molar mass is 92.0 g/mol. What is the molecular formula?

  26. 26.A liquid hydrocarbon contains 72.0 g C and 6.0 g H. Atomic masses: C 12.0, H 1.0. The molar mass is 78.0 g/mol. What is the molecular formula?

  27. 27.An iron oxide is 70.0% Fe and 30.0% O by mass. Atomic masses: Fe 56.0, O 16.0. The molar mass is 160 g/mol. What is the molecular formula?

  28. 28.The equation is already balanced: N2 + 3 H2 → 2 NH3. How many moles of NH3 form from 4.00 mol N2 when H2 is in excess?

  29. 29.Water forms by 2 H2 + O2 → 2 H2O, already balanced. How many moles of O2 react with 6.00 mol H2?

  30. 30.Methane burns as CH4 + 2 O2 → CO2 + 2 H2O, already balanced. How many moles of O2 are required for 5.00 mol CH4?

  31. 31.Aluminum burns as 4 Al + 3 O2 → 2 Al2O3, already balanced. How many moles of Al2O3 form from 8.00 mol Al when O2 is in excess?

  32. 32.Ethane burns as 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O, already balanced. How many moles of CO2 form from 3.00 mol C2H6 when O2 is in excess?

  33. 33.Limestone decomposes as CaCO3 → CaO + CO2, already balanced. How many moles of CO2 form from 0.250 mol CaCO3?

  34. 34.Sulfur dioxide is oxidized as 2 SO2 + O2 → 2 SO3, already balanced. How many moles of SO3 form from 0.800 mol O2 when SO2 is in excess?

  35. 35.Iron ore is reduced as Fe2O3 + 3 CO → 2 Fe + 3 CO2, already balanced. How many moles of CO are needed to produce 6.00 mol Fe?

  36. 36.Dinitrogen tetroxide dissociates as N2O4 → 2 NO2, already balanced. How many moles of NO2 form from 1.50 mol N2O4?

  37. 37.Hydrogen burns as 2 H2 + O2 → 2 H2O. What mass of H2O forms from 8.00 g H2 when O2 is in excess? Molar masses: H2 2.00 g/mol, H2O 18.0 g/mol.

  38. 38.Carbon burns as C + O2 → CO2. What mass of CO2 forms from 6.00 g C when O2 is in excess? Molar masses: C 12.0 g/mol, CO2 44.0 g/mol.

  39. 39.Sodium reacts as 2 Na + Cl2 → 2 NaCl. What mass of NaCl forms from 4.60 g Na when Cl2 is in excess? Molar masses: Na 23.0 g/mol, NaCl 58.5 g/mol.

  40. 40.Heating drives CaCO3 → CaO + CO2. What mass of CaO forms from 50.0 g CaCO3? Molar masses: CaCO3 100 g/mol, CaO 56.0 g/mol.

  41. 41.Ammonia is made by N2 + 3 H2 → 2 NH3. What mass of NH3 forms from 14.0 g N2 when H2 is in excess? Molar masses: N2 28.0 g/mol, NH3 17.0 g/mol.

  42. 42.A chlorate decomposes as 2 KClO3 → 2 KCl + 3 O2. What mass of O2 forms from 24.5 g KClO3? Molar masses: KClO3 122.5 g/mol, O2 32.0 g/mol.

  43. 43.Rust forms as 4 Fe + 3 O2 → 2 Fe2O3. What mass of Fe2O3 forms from 11.2 g Fe when O2 is in excess? Molar masses: Fe 56.0 g/mol, Fe2O3 160 g/mol.

  44. 44.Propane burns as C3H8 + 5 O2 → 3 CO2 + 4 H2O. What mass of CO2 forms from 11.0 g C3H8 when O2 is in excess? Molar masses: C3H8 44.0 g/mol, CO2 44.0 g/mol.

  45. 45.Aluminum dissolves as 2 Al + 6 HCl → 2 AlCl3 + 3 H2. What mass of H2 forms from 5.40 g Al when HCl is in excess? Molar masses: Al 27.0 g/mol, H2 2.00 g/mol.

  46. 46.The balanced reaction is N2 + 3 H2 → 2 NH3. A mixture starts with 2.00 mol N2 and 3.00 mol H2. How many moles of the excess reactant remain?

  47. 47.Water forms by the balanced equation 2 H2 + O2 → 2 H2O. Starting amounts are 5.00 mol H2 and 2.00 mol O2. How many moles of the excess reactant remain?

  48. 48.Methane burns by CH4 + 2 O2 → CO2 + 2 H2O, already balanced. The feed is 3.00 mol CH4 and 4.00 mol O2. How many moles of the excess reactant remain?

  49. 49.Aluminum burns as 4 Al + 3 O2 → 2 Al2O3, already balanced. The charge is 8.00 mol Al and 3.00 mol O2. How many moles of the excess reactant remain?

  50. 50.The contact step is 2 SO2 + O2 → 2 SO3, already balanced. A reactor holds 5.00 mol SO2 and 2.00 mol O2. How many moles of the excess reactant remain?

  51. 51.Coke burns as C + O2 → CO2, already balanced. The feed is 4.00 mol C and 2.50 mol O2. How many moles of the excess reactant remain?

  52. 52.Ethane burns as 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O, already balanced. The charge is 2.00 mol C2H6 and 14.0 mol O2. How many moles of the excess reactant remain?

  53. 53.The reduction is Fe2O3 + 3 CO → 2 Fe + 3 CO2, already balanced. Starting amounts are 1.00 mol Fe2O3 and 6.00 mol CO. How many moles of the excess reactant remain?

  54. 54.Hydrogen sulfide burns as 2 H2S + 3 O2 → 2 SO2 + 2 H2O, already balanced. The mixture has 4.00 mol H2S and 3.00 mol O2. How many moles of the excess reactant remain?

  55. 55.A preparation has a theoretical yield of 40.0 g and an actual yield of 30.0 g. What is the percent yield?

  56. 56.A student isolates 20.0 g of product. The calculated theoretical yield is 25.0 g. What is the percent yield?

  57. 57.An esterification is expected to give 10.0 g and actually gives 9.00 g. What is the percent yield?

  58. 58.Carbon burns as C + O2 → CO2. From 3.00 g C, the actual mass of CO2 is 5.50 g. Molar masses: C 12.0 g/mol, CO2 44.0 g/mol. What is the percent yield?

  59. 59.The reaction is 2 H2 + O2 → 2 H2O. From 4.00 g H2, the actual mass of water is 27.0 g. Molar masses: H2 2.00 g/mol, H2O 18.0 g/mol. What is the percent yield?

  60. 60.Limestone decomposes as CaCO3 → CaO + CO2. From 25.0 g CaCO3, the actual mass of CaO is 8.40 g. Molar masses: CaCO3 100 g/mol, CaO 56.0 g/mol. What is the percent yield?

  61. 61.Ammonia forms by N2 + 3 H2 → 2 NH3. From 7.00 g N2, the actual mass of NH3 is 6.80 g. Molar masses: N2 28.0 g/mol, NH3 17.0 g/mol. What is the percent yield?

  62. 62.Salt forms by 2 Na + Cl2 → 2 NaCl. From 4.60 g Na, the actual mass of NaCl is 4.68 g. Molar masses: Na 23.0 g/mol, NaCl 58.5 g/mol. What is the percent yield?

  63. 63.Rust forms as 4 Fe + 3 O2 → 2 Fe2O3. From 11.2 g Fe, the actual mass of Fe2O3 is 12.0 g. Molar masses: Fe 56.0 g/mol, Fe2O3 160 g/mol. What is the percent yield?

  64. 64.What is the molarity of a solution made by dissolving 0.200 mol NaCl in water to a total volume of 250 mL?

  65. 65.Hydrochloric acid is prepared by dissolving 0.500 mol HCl and diluting to 100 mL. What is the molarity?

  66. 66.A 2.00 M stock solution is diluted by transferring 25.0 mL into a flask and adding water until the volume is 0.250 L. What is the final molarity?

  67. 67.How many milliliters of 6.00 M HCl are needed to prepare 0.500 L of 1.20 M HCl?

  68. 68.Potassium hydroxide, 0.150 mol, is dissolved and diluted to 500 mL. What is the molarity of the solution?

  69. 69.A student pipets 50.0 mL of 0.400 M NaOH into a flask and dilutes it to 0.200 L. What is the new molarity?

  70. 70.How many milliliters of 4.00 M H2SO4 are needed to make 0.250 L of 0.800 M H2SO4?

  71. 71.Glucose, 1.00 mol, is dissolved in water and the solution is brought to 250 mL. What is the molarity?

  72. 72.Diluting 40.0 mL of stock acid to 0.200 L produces a 1.50 M solution. What was the molarity of the stock?

  73. 73.Silver chloride precipitates by AgNO3 + NaCl → AgCl + NaNO3. What mass of AgCl forms from 0.200 mol AgNO3 when NaCl is in excess? The molar mass of AgCl is 143.5 g/mol.

  74. 74.A 25.0 mL sample of 0.200 M HCl is titrated with NaOH. The reaction is HCl + NaOH → NaCl + H2O. How many moles of NaOH are required?

  75. 75.Barium sulfate precipitates by BaCl2 + Na2SO4 → BaSO4 + 2 NaCl. How many moles of BaSO4 form from 0.150 mol BaCl2 when Na2SO4 is in excess?

  76. 76.A 40.0 mL portion of 0.500 M NaOH is neutralized by H2SO4. The reaction is 2 NaOH + H2SO4 → Na2SO4 + 2 H2O. How many moles of H2SO4 are required?

  77. 77.Calcium carbonate precipitates by CaCl2 + Na2CO3 → CaCO3 + 2 NaCl. What mass of CaCO3 forms from 0.100 mol CaCl2 when Na2CO3 is in excess? The molar mass of CaCO3 is 100 g/mol.

  78. 78.A 15.0 mL aliquot of 0.400 M KOH is titrated with HCl. The reaction is KOH + HCl → KCl + H2O. How many moles of HCl are required?

  79. 79.Lead(II) iodide precipitates by Pb(NO3)2 + 2 KI → PbI2 + 2 KNO3. How many moles of PbI2 form from 0.0800 mol Pb(NO3)2 when KI is in excess?

  80. 80.A 50.0 mL sample of 0.100 M Ca(OH)2 is titrated with HCl. The reaction is Ca(OH)2 + 2 HCl → CaCl2 + 2 H2O. How many moles of HCl are required?

  81. 81.Magnesium hydroxide precipitates by MgCl2 + 2 NaOH → Mg(OH)2 + 2 NaCl. What mass of Mg(OH)2 forms from 0.0500 mol MgCl2 when NaOH is in excess? The molar mass of Mg(OH)2 is 58.0 g/mol.

  82. 82.The reaction is CaCO3 → CaO + CO2. Complete decomposition of 0.500 mol CaCO3 produces CO2. What volume does that CO2 occupy at 0.821 atm and 300 K? Use R = 0.0821 L atm / mol K.

  83. 83.Water decomposes as 2 H2O → 2 H2 + O2. What volume of O2 forms from 2.00 mol H2O at 1.642 atm and 400 K? Use R = 0.0821 L atm / mol K.

  84. 84.Ammonia forms by N2 + 3 H2 → 2 NH3. If 3.00 mol H2 react completely, what volume of NH3 forms at 0.821 atm and 250 K? Use R = 0.0821 L atm / mol K.

  85. 85.A 12.0 L sample of O2 is held at 0.821 atm and 300 K. How many moles of O2 are present? Use R = 0.0821 L atm / mol K.

  86. 86.What pressure does 2.00 mol of N2 exert in a 10.0 L vessel at 500 K? Use R = 0.0821 L atm / mol K.

  87. 87.At what temperature does 1.00 mol of gas occupy 20.0 L at 0.821 atm? Use R = 0.0821 L atm / mol K.

  88. 88.The decomposition is 2 KClO3 → 2 KCl + 3 O2. Complete reaction of 0.200 mol KClO3 produces O2. What volume does that O2 occupy at 0.821 atm and 400 K? Use R = 0.0821 L atm / mol K.

  89. 89.Methane burns as CH4 + 2 O2 → CO2 + 2 H2O. Combustion of 0.250 mol CH4 produces CO2 collected at 1.642 atm and 400 K. What is the CO2 volume? Use R = 0.0821 L atm / mol K.

  90. 90.A reaction produces 0.800 mol of H2. What volume does that hydrogen occupy at 0.821 atm and 350 K? Use R = 0.0821 L atm / mol K.

  91. 91.What is the percent by mass of H in CH4? The molar mass of CH4 is 16.0 g/mol, and the hydrogen in the formula contributes 4.0 g per mole.

  92. 92.What is the percent by mass of O in SO3? The molar mass of SO3 is 80.0 g/mol, and the oxygen in the formula contributes 48.0 g per mole.

  93. 93.What is the percent by mass of Fe in Fe2O3? The molar mass of Fe2O3 is 160 g/mol, and the iron in the formula contributes 112 g per mole.

  94. 94.What is the percent by mass of Ca in CaCO3? The molar mass of CaCO3 is 100 g/mol, and the calcium in the formula contributes 40.0 g per mole.

  95. 95.What is the percent by mass of C in C2H6? The molar mass of C2H6 is 30.0 g/mol, and the carbon in the formula contributes 24.0 g per mole.

  96. 96.What is the percent by mass of N in N2H4? The molar mass of N2H4 is 32.0 g/mol, and the nitrogen in the formula contributes 28.0 g per mole.

  97. 97.What is the percent by mass of Mg in MgO? The molar mass of MgO is 40.0 g/mol, and the magnesium in the formula contributes 24.0 g per mole.

  98. 98.What is the percent by mass of O in CuO? The molar mass of CuO is 80.0 g/mol, and the oxygen in the formula contributes 16.0 g per mole.

  99. 99.What is the percent by mass of N in NH4NO3? The molar mass of NH4NO3 is 80.0 g/mol, and the nitrogen in the formula contributes 28.0 g per mole.

  100. 100.A 2.50 g sample of CuSO4.xH2O loses 0.90 g of water when heated. The molar mass of CuSO4 is 160 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?

  101. 101.A 2.86 g sample of Na2CO3.xH2O leaves 1.06 g of anhydrous Na2CO3 after heating. The molar mass of Na2CO3 is 106 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?

  102. 102.Heating 2.46 g of MgSO4.xH2O leaves 1.20 g of anhydrous MgSO4. The molar mass of MgSO4 is 120 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?

  103. 103.A 2.44 g sample of BaCl2.xH2O loses 0.36 g of water on heating. The molar mass of BaCl2 is 208 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?

  104. 104.A 2.38 g sample of CoCl2.xH2O leaves 1.30 g after the water is driven off. The molar mass of CoCl2 is 130 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?

  105. 105.Heating CaCl2.xH2O drives off 0.72 g of water and leaves 1.11 g of anhydrous CaCl2. The molar mass of CaCl2 is 111 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?

  106. 106.A 4.64 g sample of Na2SO4.xH2O leaves 2.84 g of anhydrous Na2SO4. The molar mass of Na2SO4 is 142 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?

  107. 107.A 1.89 g sample of CuCl2.xH2O loses 0.54 g of water when heated. The molar mass of CuCl2 is 135 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?

  108. 108.Heating FeSO4.xH2O leaves 1.52 g of anhydrous FeSO4 and releases 1.44 g of water. The molar mass of FeSO4 is 152 g/mol, and the molar mass of H2O is 18.0 g/mol. What is x?