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Homework Help: Need Help With My Unit Assignment (DUE December 5th)

  1. Nov 29, 2008 #1
    Need Help With My Unit Assignment!!!!(DUE December 5th)

    Ok guys I really need help with My Chemistry Unit Assignment, it is due in a couple of days and I haven't even started it because I don't really understand it. My teacher sucks at teaching and I also pay attention to him everyday. It is 5 questions:

    1.) Nitric Acid is produced commercially by the Ostwald process, represented by the following equations:

    4 NH3(g) + 5 O2(g) → 4 NO (g) + 6 H2O(g)
    2 NO(g) + O2(g) → 2 NO2(g)
    3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g)

    What mass of NH3 must be used to produce 1.0 x 106 kg of nitric acid by this process? Assume 100% yield in each reaction and assume that the NO produced in the third step is not recycled.

    2.) Hydrogen peroxide is used as a cleaning agent in the treatment of cuts and abrasions for several reasons. It is an oxidizing agent that can directly kill many microorganisms; it decomposes upon contact with blood, releasing elemental oxygen gas (which inhibits the growth of anaerobic microorganisms); and it foams upon contact with blood, which provides a cleansing action. In the laboratory, small quantities of hydrogen peroxide can be produced by the reaction of barium peroxide (BaO2) with hydrochloric acid.

    a. What amount of hydrogen peroxide should result when 1.50 g of barium peroxide reacts with 25.0 mL of 0.030 M hydrochloric acid?

    b. Which reactant is present in excess? How much? (If the excess reactant is barium peroxide, the answer must be given in grams, and if it is hydrochloric acid, the answer must be given in milliliters).

    3.) A sheet of gold weighing 10.0 g and at a temperature of 18.0 oC is placed flat on a sheet of iron weighing 20.0 g and at a temperature of 55.6 oC. What is the final temperature of the combined metals? (Assume that no heat is lost to the surroundings).

    4.) Consider the reaction of hydrochloric acid with magnesium.

    a. Write the balanced thermochemical equation describing this reaction. (∆Hrxn = -460 kJ/mol)

    b. What type of reaction is this?

    c. Is this reaction exothermic or endothermic?

    d. What volume of 5.0 M hydrochloric acid is needed to react completely with 3.00 g of magnesium?

    e. How much heat energy is evolved in this reaction?

    f. Assume that the solution is entirely water, with a specific heat of 4.184 J/g∙C, what is the final temperature of the solution? The starting temperature water 21 oC.

    5.) The temperature of a person with an extremely high fever can be lowered with a sponge bath of 2-propanol (rubbing alcohol). The heat of vaporization of 2-propanol is 11.1 kcal/mol.

    a. How many kilocalories of heat are removed from the skin of a person when 175 g of 2-propanol evaporates? How many kilojoules?

    b. How many kilograms of water would this energy loss cool in lowering the temperature from 40.0oC to 36.0oC?

    Thats all the questions, Please help me by telling me the answer and how you got the answer by showing work. It's dimensional Analysis work if doing math. Thanks Guys :D
  2. jcsd
  3. Nov 29, 2008 #2


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    Staff: Mentor

    Re: Need Help With My Unit Assignment!!!!(DUE December 5th)

    You just don't ask. You try, you tell us what you did, we push you in the right direction.
  4. Nov 29, 2008 #3
    Re: Need Help With My Unit Assignment!!!!(DUE December 5th)

    Yea its kind of hard for me to do all this :(, I mean I do not understand a lot of what its telling me to do.
  5. Dec 1, 2008 #4
    Re: Need Help With My Unit Assignment!!!!(DUE December 5th)

    You should be able to have a stab at the first one.... You have the balanced equations and you're told that you have to produce what I assume is 1.0 x 10^6 (100,000) kg of nitric acid.

    If you know how many moles that is, then from the stoichiometry shown in the equations you can work out how much NO you need, and therefore how much NH3 is ultimately needed.

  6. Dec 1, 2008 #5


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    Homework Helper
    Education Advisor
    Gold Member

    Re: Need Help With My Unit Assignment!!!!(DUE December 5th)

    For question #2, can you write a balanced reaction between hydrochloric acid and barium peroxide to produce hydrogen peroxide? Note that Barium ion in the reactant is a "plus 2" oxidation state.
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