Unit 10 Quiz--Heats of Reaction--Thurston High Chemistry

Multiple Choice (Choose the best answer.)

  1. How much energy (in calories and in Joules) will it take to raise the temperature of 75.0 g of water from 20.0 to 55.0 oC? ( Specific Heat = 1 cal / ( g oC ) and 4.184 J / ( g oC ) )

    2630 cal and 630. J

    2630 cal and 1.1 x 10 4 J

    1.1 x 10 4 cal and 2630 J

    630. cal and 2630 J

    None of these are correct.

  2. Indentify the FASLE statement about the reaction below: 1/8 S8 (s) + H2 (g) + 2 O2 (g) H2SO4 (l) + 194 Kcal

    The reaction is exothermic

    1 mole of O2 could produce 97 Kcal.

    4 g of H2 could produce 388 Kcal

    HRxn is + 194 Kcal

    The temperature would increase during the reaction.

    Use the data table at right to answer questions 3 and 4. In the reaction, MgO is dissolved in HCl.

    Mass Mass MgO (g)2.00
    Mass of 1.00 M HCl and MgO Solution (g)1.00 x 10 2
    Beginning Temperature of Solution (oC)21.2
    Ending Temperature of Solution (oC)30.0

  3. How much energy is liberated in the reaction?

    0.0166 Kcal

    0.880 Kcal

    0.898 Kcal

    8.8 Kcal

    16.6 Kcal

  4. What is the heat of reaction in Kcal per mole of MgO?

    0.440 Kcal / mol

    0.440 Kcal / mol

    0.880 Kcal / mol

    17.6 Kcal / mol

    None of these are correct.

  5. Which of the following statements is/are correct?

    I. Energy is required to break chemical bonds.
    II. In exothermic reactions, more energy is required to break bonds than is released in making bonds.
    III. A (-) HRxn indicates an exothermic reaction.

    I only

    II only

    I and II only

    I and III only

    I, II, and III are correct.

    Use the table of bond energies to answer quesions 6 - 8 for the reaction:

    2 H-H (g) + O=O (g) 2 H-O-H (g)

    Type of Bond

    Energy (KJ/mol)

    H-H

    432

    H-O

    459

    O=O

    494

  6. How much energy is required to break all the bonds in the reactants?

    432 KJ

    926 KJ

    1358 KJ

    1817 KJ

    None of these are correct.

  7. How much energy is produced by forming all the bonds in the reactants?

    459 KJ

    918 KJ

    1377 KJ

    2295 KJ

    None of these are correct.

  8. Use your answers to questions 6 and 7 to find the H Rxn.

    - 478 KJ

    - 467 KJ

    + 478 KJ

    + 467 KJ

    None of these are correct.

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