Energy in Chemical and Nuclear Reactions


True/False

  1. It requires energy to break a chemical bond.

  2. The reaction C (s) + O2 (g) CO2 (g) + 94.0 Kcal indicates that the reaction is exothermic.

  3. An exothermic reaction feels cold.

  4. In an exothermic reaction, the energy stored in the products is less than that stored in the reactants.

  5. The heat of reaction for an exothermic reaction is a negative number.

  6. Gases possess a great deal of translational motion.

  7. Molecules of solids are free to rotate.

  8. The reaction + + + 3 could result in a chain reaction.

  9. Nuclear fission produces more energy than nuclear fusion per mole of reactant.

  10. Nuclear reactions release more energy than typical chemical reactions because they result in mass changing to energy.

Multiple Choice (Choose the best answer.)

  1. The graph at right shows ____

    the energy of the reactants is greater than the energy of the products.

    the energy of the products is greater than the energy of the reactants.

    an exothermic reaction.

    a reaction that gives off heat.

    More than one of the above is correct.

  2. In the Heat of a Burning Candle Experiment, you used a candle to heat up water in a tin can. In the lab you assumed that _____

    heat from the room always flowed into the water in the tin can.

    heat from the water in the tin can always flowed out into the room.

    the heat lost to the room equalled the heat gained from the room.

    All of the above are correct.

    None of the above are correct.

  3. In the reaction, C (s) + O2 (g) CO2 (g) + 94.0 Kcal, the combustion of 0.25 moles of carbon would produce how much energy?

    23.5 Kcal

    94.0 Kcal

    282 Kcal

    367 Kcal

    None of the above are correct.

  4. Using the reaction in problem 3, how much energy would accompany the production of 15.0 g of CO2?

    0.00360 Kcal

    7.02 Kcal

    32.0 Kcal

    62000 Kcal

    None of the above are correct.

  5. Using the reaction in problem 3, the combustion of 0.750 g of C could raise the temperature of 125 g of H2O how many oC?

    0.0470 oC

    12.0 oC

    83.6 oC

    734000 oC

    None of the above are correct.

  6. Use the formation reactions given below to calculate the energy in the reaction: H2O (g) H2O (l)
    H = - 10.5 Kcal

    H = + 10.5 Kcal

    H = - 126.1 Kcal

    H = + 126.1 Kcal

    None of the above are correct.

  7. Use the reactions below to calculate the energy released when one mole of ethane, C2H6, is burned to form gaseous products.

    131.0 Kcal

    172.0 Kcal

    341.2 Kcal

    372.7.2 Kcal

    None of these are correct.

  8. Which one of the following statements concerning molecular motions is TRUE?

    In a solid, rotational motion is predominant.

    In a liquid, as temperature is cooled, the average translational motion increases.

    For a given substance, rotational motions of molecules are greater in the solid than in the liquid state.

    There is a temperature above which no molecule can exist.

    Plasma is formed when molecules become ionized.

  9. In the Heat of Reaction for the Combustion of Mg experiment, you reacted Mg (s) with HCl to determine the heat of reaction (H) in Kcal/mol of Mg. How would the value of H have changed if you would have used twice as much Mg while keeping everything else the same.

    H would double because the heat produced would double.

    H would be one-half because the mole of Mg doubles.

    H would stay the same.

    It is impossible to say because not enough information is given.

    None of these are correct.

  10. Order the following types of reactions from lowest energy to highest energy:

    I, II, and III

    I, III, and II

    III, II, and I

    II, I, and III

    II, III, and I

Problem Solving (Show All Work. Use significant figures.)

1. In a reaction similar to the Heat of Reaction for the Combustion of Mg experiment, 1.04 g of MgO was reacted with 100.0 mL of 1.0 M HCl. The temperature of the reaction rose from 22.0 oC to 26.8 oC.

a) Calculate the temperature change of the solution.

b) Calculate the heat produced in Kcal.

c) Calculate the moles of MgO reacted.

d) Calculate the heat of reaction (H) in Kcal/mol MgO.


2. Use your table of heats of reactions to find the energy absorbed or given off when C3H8 (g) is burned.

a) Write a balanced combustion reaction.

b) Calculate the energy absorbed or released.

c) Indicate whether the reaction is endothermic or exothermic.


3. How much energy would result from the conversion of 0.0025 g of a substance to energy? Remember that c = 3.00 x 10 8 m/s and that E = mc 2 requires that masses be in Kilograms so that E is in Joules.

 

 

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