Stoichiometry & Energy Worksheet

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PROBLEMS:

  1. For every mole of glucose sugar (C6H12O6) burned with oxygen gas to produce carbon dioxide & water, 669 kcal of energy is released.
    1. Write a balanced equation for this reaction.
    2. In order to release 103 kcal of energy, what volume of waste carbon dioxide (at STP) is produced?
  2. Both methanol (CH3OH) and ethanol (C2H5OH) are highly flammable alcohols, and produce carbon dioxide gas and water when burned in air. Methanol produces 174 kcal of energy per mole of alcohol burned, while ethanol produces 327 kcal of energy per mole of alcohol burned.
    1. Write balanced equations for both of these combustion reactions.
    2. Which fuel produces more energy per pound of fuel? (1 lb. = 454 grams)
    3. An IPS alcohol burner holds about 100 g. of ethanol. How much energy is produced when this much ethanol is burned?
  3. Boron hydride compounds contain extraordinary amounts of heat energy. In the 1960's much research was done on possible rocket fuels made with them. For example, pentaboron nonahydride produces 1080 kcal of energy per mole when burned in air to produce diboron trioxide and water.
    1. Write a balanced equation for this reaction, and include energy.
    2. Given 1.00 kg of pentaboron nonahydride and 2.00 kg of oxygen, which is the limiting reagent?
    3. How much heat energy could be produced under these conditions?
  4. The fuel "water gas" is a mixture of carbon monoxide and hydrogen. It is made by passing steam over coal (monatomic carbon). This is an endothermic reaction, requiring 31.4 kcal per mole of coal.
    1. Write a balanced equation for this reaction, including energy.
    2. How much energy is needed to convert 1 metric ton (1000 kg) of coal?
    3. How much water gas could be produced under the conditions of "b"?
  5. In the tin-oxide lab we produced the brown gas nitrogen dioxide. This reacts with carbon monoxide (a normal component of the atmosphere) to produce carbon dioxide and colorless nitrogen monoxide. Heat is also produced, at the rate of 54 kcal per mole of nitrogen dioxide.
    1. Write a balanced equation for this reaction, including energy.
    2. Given 2.00 g of carbon monoxide and 3.00 g of nitrogen dioxide, which is the limiting reagent?
    3. Under the conditions of "b", how much energy will be released?

ANSWERS

  1.  
    1. C6H12O6 (s) + 6O2 (g) -> 6CO2 (g) + 6H2O (l) + 669 kcal
    2. 201 L. carbon dioxide
  2.  
    1. C2H5OH + 3O2 -> 2CO2 + 3H2O + 327 kcal and 2CH3OH + 3O2 -> 2CO2 + 4H2O + 348 kcal
    2. 454 g. methanol produces 2470 kcal while 454 g. ethanol produces 3320 kcal , so ethanol burns more energy per pound of fuel than methanol
    3. 709 kcal
  3.  
    1. 2B5H9 + 12O2 -> 5B2O3 + 9H2O + 2160 kcal
    2. oxygen limits the reaction
    3. 1.13 x 104 kcal
  4.  
    1. C (s) + H2O (g) + 31.4 kcal -> CO (g) + H2 (g)
    2. 2.62 x 106 kcal
    3. 2.50 x106 g. or 2.50 metric tons of water gas (CO + H2)
  5.  
    1. CO (g) + NO2 (g) -> CO2 + NO (g) + 54 kcal
    2. nitrogen dioxide limits the reaction
    3. 3.5 kcal

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