California Chemistry Standards Review - Part 4

Gap-fill exercise

Fill in all the gaps, then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!

Conservation of Mass and Stoichiometry

  1. Students know how to describe chemical reactions by writing balanced equations.
    Balance the following equations:
    Ag + S8 Ag2S

    Al2O3 Al + O2

    AlBr3 + Cl2 AlCl3 + Br2

    C5H12 + O2 CO2 + H2O

    C4H10 + O2 CO2 + H2O

  2. Students know the quantity one mole is set by defining one mole of - atoms to have a mass of exactly 12 grams.
  3. Students know one mole equals x 23 particles (atoms or molecules).
  4. Students know how to determine the molar mass of a molecule from its chemical formula and a table of atomic masses and how to convert the mass of a molecular substance to moles,
    number of particles, or volume of gas at standard temperature and pressure.

    • The molar mass of ethane gas, C2H6, is grams per mole.
    • 90 grams of ethane would contain moles of ethane molecules.
    • 90 grams of ethane represents about x 1024 molecules of ethane
    • At standard conditions, 90 grams of ethane would occupy liters.

  5. Students know how to calculate the masses of reactants and products in a chemical reaction from the mass of one of the reactants or products and the relevant atomic masses.
    Ethane burns in oxygen as indicated in the following equation:
    2 C2H6 + 7 O2 → 4 CO2 + 6 H2O

    Stoichiometric calculation tells us that grams of CO2 are produced from the complete combustion of 60 grams of ethane. That mass of carbon dioxide would occupy liters at standard conditions.