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Homework:
Chemical Ratios

a.k.a. Stoichiometry

Balance the following chemical equations.

  1.     K2O +     H2O Arrowsngl     KOH
  2.     Na2O2 +     H2O Arrowsngl     NaOH +     O2
  3.     H3AsO4 Arrowsngl     As2O5 +     H2O
  4.     Al2(SO4)3 +     Ca(OH)2 Arrowsngl     Al(OH)3 +     CaSO4
  5.     H3BO3 Arrowsngl     H4B6O11 +     H2O
  6.     H2S +     Cl2 Arrowsngl     S8 +     HCl
  7.     C7H16 +     O2 Arrowsngl     CO2 +     H2O
  8.     Na +     NaNO3 Arrowsngl     Na2O +     N2
  9.     C3H8 +      O2 Arrowsngl      CO2 +      H2O
  10.     NH3 +     NO Arrowsngl     N2 +     H2O

Molar Mass

Find the molar mass of each of the following chemicals. Express your answer in units of grams per mole (g/mol).

  1. pure sodium
  2. oxygen gas
  3. pure copper
  4. pure iron
  5. sodium chloride
  1. water
  2. iron(III) oxide
  3. sodium hydroxide
  4. ammonium chloride
  5. calcium sulfate

Molar Masses

Calculate the molar mass in grams per mole (g/mol) for each of the following chemicals. Use five significant figures in your answer. Use all available digits from your periodic table.

  1. K2O
  2. H2O
  3. KOH
  4. C3H8
  5. O2
  1. CO2
  2. NH3
  3. NO
  4. N2
  5. Al2(SO4)3

Stoichiometry

You must balance the chemical equations on the front of this paper before completing the following problems. In each one you are asked to use the ratios implied by the equation to make predictions about numbers of molecules, numbers of moles or the mass the chemicals involved in the reaction.

  1. Equation 1 from the front of this paper. If you have 1 molecule of K2O how many molecules of water will react with it?
  2. Equation 1 from the front of this paper. If you have 1 molecule of K2O how many molecules of KOH will be produced?
  3. Equation 1 from the front of this paper. If you have 1,000 molecules of K2O how many molecules of water will react with them?
  4. Equation 1 from the front of this paper. If you have 1.5 × 106 molecules of K2O how many molecules of KOH will be produced?
  5. Equation 9 from the front of this paper. If you have 1 mole of C3H8 then how many moles of oxygen gas do you need?
  1. Equation 9 from the front of this paper. If you have 2 moles of C3H8 then how many moles of oxygen gas do you need?
  2. Equation 9 from the front of this paper. If you have 12 moles of C3H8 then how many moles of carbon dioxide gas will be prodcued?
  3. Equation 9 from the front of this paper. If you have 44.1 g of C3H8 then how many moles of water vapor will be prodcued?
  4. Equation 9 from the front of this paper. If you have 44.1 g of C3H8 then how many moles of carbon dioxide gas will be prodcued?
  5. Equation 9 from the front of this paper. If you have 88.2 g of C3H8 then how many grams of water vapor gas will be prodcued?




The following section will not print because, although they are good problems, they are too hard for use in the introduction of this skill. Perhaps in the near future I will create another sheet exclusively for these problems.



page break
 

There are two problems on this page. Each one has multiple parts: you must balance the equation and use chemical ratios (stoichiometry) to answer the questions.

  1. Chromium compounds are valued for their very bright colors. Ammonium dichromate is a vivid orange compound and when it is ignited it breaks down into chromium(III) oxide, nitrogen gas and water. Balance the following equation and answer the questions below.
    (NH4)2Cr2O7Arrowsngl    Cr2O3 +    N2 +    H2O


    1. How many moles of water are produced if one mole of ammonium dichromate is ignited?
    2. How many moles of nitrogen are produced if one mole of ammonium dichromate is ignited?
    3. How many moles of chromium(III) oxide are produced if 5 mol of ammonium dichromate is ignited?
    4. If you have 5.7 g of ammonium dichromate how many moles of nitrogen gas are produced?
    5. Taking the same 5.7 g of ammonium dichromate, how many grams of nitrogen gas are produced?
    6. Taking the same 5.7 g of ammonium dichromate, how many grams of water are produced?
  2. The solid rocket boosters used with the NASA space shuttle use a mixture of aluminum and ammonium perchlorate for fuel. This produces an incredible amount of energy when burnt and requires no oxygen from the atmosphere to work. Balance the following equation describing the reaction which is likely to occur when the rockets fire. Then answer the questions.
    Al +    NH4ClO4Arrowsngl    Al2O3 +    AlCl3 +    NO +    H2O


    1. Given 150 mol of aluminum, how many moles of ammonium perchlorate are needed to use up all of the aluminum?
    2. Obviously, the rocket boosters are large. What mass of ammonium perchlorate is needed for every kilogram of aluminum? (1 kg = 1,000 g).
    3. If a booster is loaded with 72,576 kg of aluminum, how many kilograms of ammonium perchlorate are needed?
The information about the solid rocket booster came from
http://www-pao.ksc.nasa.gov/nasafact/count2.htm
where it states that the total fuel mass of a solid
rocket booster is 453,600 kilograms. It also says
that Al powder makes up 16% of that mass.
Last updated: Jun 05, 2008 Home