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

Multiple Choice (Choose the best answer.)

Use the reaction at right to answer questions 1 - 3: 1/2 N2 (g) + 3/2 H2 (g) NH3 (g) + 46.0 KJ

  1. 2.0 moles of 1/2 N2 (g) would produce how much energy?

    46. KJ

    92 KJ

    180 KJ

    None of the above are correct.

    Not enough information is given to answer the question.

  2. 10.0 g of H2 (g) would produce how much energy?

    0.072 Kcal

    150 Kcal

    345 Kcal

    1380 Kcal

    None of the above are correct.

  3. Combine these reactions to find the heat of reaction (H rxn) when H2O (l) is vaporized to make H2O (g).

    H2 (g) + 1/2 O2 H2O (g) + 57.8 Kcal

    H2 (g) + 1/2 O2 H2O (l) + 68.3 Kcal

    H rxn= 10.5 Kcal / mol

    H rxn= - 10.5 Kcal / mol

    H rxn= 126.1 Kcal / mol

    H rxn= - 126 Kcal / mol

    None of these are correct.

  4. Combine these reactions to determine how much energy is released in the combustion of propane:

    C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g)

    3 C (s) + 4 H2 (g) C3H8 (g) + 104 KJ
    C (s) + O2 (g) CO2 (g) + 393 KJ
    H2 (g) + 1/2 O2 H2O (g) + 242 KJ

    H rxn = + 531KJ

    H rxn = - 531 KJ

    H rxn = + 1650 KJ

    H rxn = - 1650 KJ

    None of the above are correct.

  5. Use the following heats of formation to find the energy absorbed or evolved when one mole of methane (CH4 ) is burned to make carbon monoxide and water?

    CH4 (g) + 3/2 O2 (g) CO (g) + 2 H2O (g)

    CH4 (g) =

    - 75 KJ / mol

    CO (g) =

    - 111 KJ / mol

    H2O (g) =

    - 242 KJ / mol

    -275 KJ

    - 520 KJ

    - 670 KJ

    It is impossible to solve because the heat of formation of O2 (g) is not listed in the table.

    None of these are correct.

  6. Given the heats of formation for the substances below, calculate the heat of combustion as one mole of NH3 (g) is burned to form NO (g) and H2O (l). (You must write your own balanced reaction!)

    NH3 (g) =

    - 46 KJ / mol

    NO (g) =

    + 90 KJ / mol

    H2O (l) =

    - 286 KJ / mol

    - 586 KJ

    - 293 KJ

    - 150 KJ

    + 150 KJ

    None of these are correct. -349 kJ/mol is the correct answer.

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