Houston community college Chem 1405
1.Acetylene gas is 92.3% carbon and 7.7% hydrogen (by mass), and its molar mass is 26 g/mol. What is its molecular formula?
a. CH
b. C2H2
c. CH4
d. C4H4
e. none of these
2. A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen (by mass). Calculate the empirical formula.
a. CH2O
b. C2H2O
c. CH4O
d. C3H6O3
e. C2HO2
3. The empirical formula for the compound having the formula H2C2O4 is
a. COH
b. COH2
c. C2H2
d. C2O4H2
e. CO2H
4. A sample of metal weighing 2.59 g is combined with oxygen; the metal oxide weighs 3.01 g. The mass percent of oxygen in the compound is
a. 86.0 %
b. 14.0 %
c. 19.0 %
d. 31.2 %
e. cannot be determined from information given
5. What is the percent (by mass) of carbon in glucose, C6H12O6.
a. 40.0 %
b. 53.3 %
c. 25.0 %
d. 6.7 %
e. none of these
6. Determine the percentage composition (by mass) of lead in PbF2.
a. 84.5 %
b. 91.6 %
c. 45.8 %
d. 54.2 %
e. 7.7 %
7. Which of the following has the largest percent by mass of carbon?
a. CaCO3
b. CO2
c. CH4
d. NaHCO3
8. Choose the pair of compounds with the same empirical formula.
a. C2H2 and C6H6
b. NaHCO3 and Na2CO3
c. K2CrO4 and K2Cr2O7
d. H2O and H2O2
9. Calculate the mass of 0.314 mol of H2SO4.
a. g
b. 30.8 g
c. g
d. g
e. g
10. Calculate the mass of sulfur in 1.74 mol of H2SO4.
a. g
b. 18.4 g
c. 55.8 g
d. g
e. g
11. Calculate the number of molecules of CH4 in 41 g CH4.
a. molecules
b. molecules
c. molecules
d. molecules
e. none of these
12. Calculate the number of moles of CH4 in 67 g CH4.
a. 0.24 mol
b. mol
c. mol
d. mol
e. 4.2 mol
13. Calculate the number of moles in 2.28 g Rb2C2O4.
a. mol
b. 113.6 mol
c. mol
d. mol
e. mol
14. A sample with atoms of copper represents how many moles of copper?
a. mol
b. mol
c. mol
d. mol
e. 7.89 mol
15. How many molecules are present in
a. molecules
b. molecules
c. molecules
d. molecules
e. none of these
16. A 50.3-g sample of H2O contains how many molecules of water?
a. molecules
b. molecules
c. molecules
d. molecules
e. none of these
17. A 60.2-mL sample of Hg (density = 13.6 g/mL) contains how many atoms of Hg?
a. atoms
b. atoms
c. atoms
d. atoms
e. none of these
18. Convert: 460.2 g MgCl2 = ____ units of MgCl2
a.
b. 4.834
c.
d.
e.
19. A 84.9-g sample of SO2 contains how many moles of SO2?
a. 1.33 mol
b. mol
c. mol
d. mol
e. none of these
20. 7.98 moles of sulfur trioxide molecules contain how many oxygen atoms?
a. 1.44 1025
b. 4.81 1024
c. 2.52 1022
d. 1.60 1024
e. 383
21. The balanced equation tells us that 4.0 mol of Cu
a. reacts with 4.0 mol of O2
b. produces 4.0 mol of CuO
c. must react with 128 g of O2
d. cannot react with oxygen
e. produces 8.0 mol of CuO
22. A 3.1-mol sample of KClO3 was decomposed according to the equation
How many moles of O2 are formed assuming 100% yield?
a. 2.1 mol
b. 2.6 mol
c. 3.1 mol
d. 1.6 mol
e. 4.7 mol
23. The rusting of iron is represented by the equation . If you have a 1.45-mol sample of iron, how many moles of Fe2O3 will there be after the iron has rusted completely?
a. 0.483 mol
b. 0.725 mol
c. 0.97 mol
d. 1.45 mol
e. 2.18 mol
24. Refer to the following equation:
How many moles of ammonia will be required to produce 11.9 mol of water?
a. 4.76 mol
b. 11.9 mol
c. 7.93 mol
d. 5.95 mol
e. none of these
25. Refer to the following equation:
How many molecules of NO2 are produced when 5.38 mol of ammonia is completely reacted?
a. 21.52
b.
c.
d. 247
e. none of these
26. Refer to the following equation:
How many molecules of water are produced if 9.12 mol of NO2 is given off?
a.
b.
c. 164.2
d.
e. none of these
27. In the reaction how many moles of ammonia would be produced from 1.21 mol of hydrogen and excess nitrogen?
a. 1.57 mol
b. 3.63 mol
c. 0.807 mol
d. 2.42 mol
e. 0.403 mol
28. Which of the following reaction mixtures would produce the greatest amount of product, assuming all went to completion? Each involves the reaction symbolized by the equation
a. 3 moles of N2 and 3 moles of H2
b. 1 mole of N2 and 6 moles of H2
c. 5 moles of N2 and 3 moles of H2
d. 1 mole of N2 and 3 moles of H2
e. All would produce the same amount of product.
29. Refer to the following unbalanced equation:
What mass of oxygen (O2) is required to react completely with 11.7 g of C6H14?
a. g
b. 20.6 g
c. 4.34 g
d. 41.3 g
e. 0.136 g
30. Refer to the following unbalanced equation:
What mass of carbon dioxide (CO2) can be produced from 25.0 g of C6H14 and excess oxygen?
a. g
b. 12.8 g
c. 76.6 g
d. 38.3 g
e. 0.290 g
31. How many molecules of carbon dioxide will be formed if 2.21 g of propane is burned in the following reaction?
a. molecules
b. molecules
c. molecules
d. molecules
e. molecules
32. What mass of carbon dioxide will be produced when 29.9 g of butane reacts with an excess of oxygen in the following reaction?
a. 181.1 g CO2
b. 90.6 g CO2
c. 11.32 g CO2
d. 119.6 g CO2
e. none of these
33. Calculate the mass of water produced when 9.47 g of methane, CH4, reacts with an excess of oxygen in the following unbalanced reaction.
a. 10.64 g H2O
b. g H2O
c. 21.3 g H2O
d. 0.526 g H2O
e. 1.18 g H2O
34. Calculate the mass of carbon dioxide produced from 22.3 g of octane, C8H18, in the following reaction.
a. 68.7 g CO2
b. 137 g CO2
c. 77.3 g CO2
d. 1.074 g CO2
e. 1.562 g CO2
ANS: A
35. For the reaction
11.9 g Cl2 is reacted with 12.0 g NaOH. How many moles of NaCl are produced?
a. 0.300 mol NaCl
b. 0.400 mol NaCl
c. 0.150 mol NaCl
d. 0.252 mol NaCl
e. 0.225 mol NaCl
36. Consider the reaction
How many moles of excess reactant are left over if we start with 39.1 g of each reactant?
a. 0.13 mol
b. 2.04 mol
c. 1.66 mol
d. 2.17 mol
e. none of these
37. Sodium and water react according to the equation
What number of moles of H2 will be produced when 4.0 mol Na is added to 1.2 mol H2O?
a. 0.6 mol
b. 2.4 mol
c. 2.0 mol
d. 1.2 mol
e. 8.0 mol
38. Determine the mass of CO2 produced when 75.5 g of CaO is reacted with 50.0 g of C according to the unbalanced equation
a. 29.6 g CO2
b. 119 g CO2
c. 59.3 g CO2
d. 36.6 g CO2
e. none of these
39. True or false? A mole ratio is used to convert the moles of a starting substance to the moles of a desired substance.
ANS: T PTS: 1 DIF: easy
40. True or false? The equation can be interpreted by saying that 1 mol of N2 reacts with 3 mol of H2 to form 2 mol of N
41. Convert atm to torr.
a. torr
b. 1.289 torr
c. 68.1 torr
d. torr
e. torr
42. Convert torr to psi.
a. 1.08 psi
b. 15.9 psi
c. psi
d. psi
e. psi
:
43. Perform the following conversion of pressure units:
193 torr = ____________ atm
a. 1.91
b. 13.1
c. 0.254
d. 3.94
e. 953
44. Determine the pressure exerted by 2.26 mol of gas in a 2.92-L container at 32°C.
a. 2.03 atm
b. 56.6 atm
c. 19.4 atm
d. 5.93 atm
e. 17.3 atm
45. What is the volume of a helium balloon that contains 1.95 mol helium at 27°C and 1.10 atm?
a. 3.93 L
b. 39.7 L
c. 48.0 L
d. 43.6 L
e. 4.32 L
46. If temperature and pressure are held constant, the volume and number of moles of a gas are
a. independent of each other
b. directly proportional
c. inversely proportional
d. equal
e. not enough information given
47. A sample of an ideal gas containing 0.637 mol is collected at 742 torr pressure and 31°C. Calculate the volume.
a. 16.3 L
b. 1.66 L
c. L
d. L
e. none of these
48. An oxygen sample has a volume of 7.01 L at 27°C and 800.0 torr. How many oxygen molecules does it contain?
a.
b.
c.
d.
e. none of these
ANS: A
52. A 4.06-L sample of carbon monoxide is collected at 55°C and 0.892 atm. What volume will the gas occupy at 1.05 atm and 20.°C?
a. 1.25 L
b. 3.86 L
c. 3.08 L
d. 4.27 L
e. none of these
49. A gas occupies 18.5 L at STP. What volume will it occupy at 735 torr and 57°C?
a. 3.99 L
b. 21.6 L
c. 15.8 L
d. 15.5 L
e. 23.1 L
ANS: E
50. A 16.4-L sample of gas at STP is heated to 55°C at 605 torr. What is the new volume?
a. 24.8 L
b. 4.15 L
c. 17.1 L
d. 15.7 L
e. 16.6 L