Solutions: Molecules and Compounds Homework Set

This problem set was developed by S.E. Van Bramer for Chemistry 145 at Widener University.


  1. For the following molecules; write the chemical formula, determine how many atoms of each element are present in one molecule, determine the molecular weight, determine the number of moles in exactly 1 gram, and the number of moles in exactly 10-6 gram.
    1. carbon dioxide
    2. iron (II) chloride
    3. zinc (I) oxide
    4. dinitrogen pentoxide
    5. potassium fluoride
    6. dihydrogen monoxide
    7. iron (III) sulfate
    8. lithium acetate

    Name Formula Atoms MW mole (1 g) mole (10-6 g)
    carbon dioxide CO2 3 44.010 0.022722 2.2722x10-8
    iron (II) chloride FeCl2 3 126.752 7.88940x10-3 7.88940x10-9
    zinc (I) oxide Zn2O 3 146.78 6.8129x10-3 6.8129x10-9
    dinitrogen pentoxide N2O5 7 108.0105 9.258360x10-3 9.25836x10-9
    potassium fluoride KF 2 58.0967 1.72127x10-2 1.72127x10-8
    dihydrogen monoxide H2O 3 18.0153 5.55084x10-2 5.55084x10-8
    iron (III) sulfate Fe2(SO4)3 17 399.885 2.50072x10-3 2.50072x10-9
    lithium acetate LiCH3COO 8 65.986 1.5155x10-2 1.5155x10-8

  2. Name the following compounds, determine the molecular weight, determine the percent composition, and determine how many moles in 8.35 grams of the compound.
    1. KI
    2. CaF2
    3. Cu2SO4
    4. Cr(NO3)6
    5. NO
    6. NO2
    7. N2O
    8. N2O4
    9. LiOH
    10. SO2

    Formula Name MW % Comp mole in 8.35 g
    KI potassium iodide 166.0028 K = 23.5528
    I = 76.44719
    5.03x10-2
    CaF2 calcium fluoride 78.075 Ca = 51.333
    F = 48.667
    0.107
    Cu2SO4 copper (I) sulfate 223.156 Cu = 28.476
    S = 14.369
    O = 28.6785
    3.74x10-2
    Cr(NO3)6 chromium (VI) nitrate 424.0206 Cr = 12.2626
    N = 19.81989
    O = 67.9188
    1.97x10-2
    NO nitrogen monoxide 30.0061 N = 46.8818
    O = 53.3205
    0.278
    NO2 nitrogen dioxide 46.0055 N = 30.5776
    O = 69.5543
    0.181
    N2O dinitrogen monoxide 44.1342 N = 63.7483
    O = 36.2517
    0.189
    N2O4 dinitrogen tetroxide 92.1324 N = 30.5374
    O = 69.4626
    9.06x10-2
    LiOH lithium hydroxide 23.948 Li = 28.98
    O = 66.786
    H = 4.2089
    0.349
    SO2 sulfur dioxide 64.065 S = 50.052
    O = 49.995
    0.130

  3. Give the chemical formula (or atomic symbol), molecular (or atomic) weight, and charge for the following ions:
    1. sulfate
    2. sulfite
    3. nitrate
    4. hydroxide
    5. nitrite
    6. chloride
    7. nitride
    8. bromide
    9. acetate
    10. carbonate

    Ion formula MW charge
    sulfite SO32- 80.0642 2-
    nitrate NO31- 62.0656 1-
    hydroxide OH1- 17.0073 1-
    nitrite NO21- 46.0662 1-
    chloride Cl1- 35.4527 1-
    nitride N3- 14.00674 3-
    bromide Br1- 79.904 1-
    acetate CH3COO1- 59.045 1-
    carbonate CO32- 60.009 2-


Please send comments or suggestions to svanbram@science.widener.edu

Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

© copyright 1996, S.E. Van Bramer
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Last Updated: Saturday, May 18, 1996