Stoichiometry HELP!!!!

Pandasarecool
Pandasarecool Posts: 508 Member
edited January 5 in Chit-Chat
Any one know anything about Stoichiometry? I am SO lost and I have a test coming up, any help at all is appreciated!!!!

Replies

  • n0ob
    n0ob Posts: 2,390 Member
    Yeah, post your problem.

    Not had inorganic in a while, but I was pretty good at it.
  • Pandasarecool
    Pandasarecool Posts: 508 Member
    Well here's one: (numbers after letters are subscript)

    One type of rocket engine uses the following reaction to develop thrust:
    7H202 + N2H4 (arrow) 2HNO3 + 8H2O

    If a rocket engine has 11.2 kg of N2H4 in it, what is the minimum mass of H2O2 necessary to allow the N2H4 to react completely?

    After much struggle, I got the answer to this, BUT I wasn't quite sure how I got it. I need to understand it fully for the test though.
    Thanks!
  • n0ob
    n0ob Posts: 2,390 Member
    There are 7 moles of hydrogen peroxide used up per mole of hydrazine in the reaction.

    11.2 kg gives you how many moles if hydrazine are going to be used. (You'll actually find this # in grams).

    So just multiply how many moles 11.2 kg of hydrazine is by 7 (since 7 moles of hydrogen peroxide are used per mole of hydrazine) nd then multiply that number by th molecular weight of the hydrogen peroxide to get your answer.

    You're actually lucky you were given a balanced equation to start...
  • Mcfatcat
    Mcfatcat Posts: 21
    OMG This was my favorite!!! Too bad I don't remember what to do.... O_o exactly..

    But, this really helps me when I did it. :3

    Also, make sure you balance the equation before you start.

    http://www.chemtutor.com/images/roadmap.gif

    http://www.chemteam.info/Stoichiometry/Stoich-Flowchart.GIF

    Lucky for you it's an easy question and KG is already mass && the equation is already balanced!!

    So 4.94 x 10^18 for N2H4 and 2.22 x 10^19 for H2O

    .___. I hope that wasn't too confusing.. If I was on my A game I'd be able to break it down for you. Hopefully someone who is come's along though if you don't. D: Hopefully that helped some, at least.
  • Pandasarecool
    Pandasarecool Posts: 508 Member
    There are 7 moles of hydrogen peroxide used up per mole of hydrazine in the reaction.

    11.2 kg gives you how many moles if hydrazine are going to be used. (You'll actually find this # in grams).

    So just multiply how many moles 11.2 kg of hydrazine is by 7 (since 7 moles of hydrogen peroxide are used per mole of hydrazine) nd then multiply that number by th molecular weight of the hydrogen peroxide to get your answer.

    You're actually lucky you were given a balanced equation to start...

    Thanks, and I know, this is one of the few balanced equations I am given.:grumble: I REALLY don't like math:sick:
  • n0ob
    n0ob Posts: 2,390 Member
    There are 7 moles of hydrogen peroxide used up per mole of hydrazine in the reaction.

    11.2 kg gives you how many moles if hydrazine are going to be used. (You'll actually find this # in grams).

    So just multiply how many moles 11.2 kg of hydrazine is by 7 (since 7 moles of hydrogen peroxide are used per mole of hydrazine) nd then multiply that number by th molecular weight of the hydrogen peroxide to get your answer.

    You're actually lucky you were given a balanced equation to start...

    Thanks, and I know, this is one of the few balanced equations I am given.:grumble: I REALLY don't like math:sick:

    Most of the work in freshman chemistry is just algebra with fancy names or units for x/y*y/z=x/z
  • snoopytwins
    snoopytwins Posts: 1,759 Member
    Aw...a flash back! But must say my preference is for quantum mechanics. ;)

    ETA...I just had a total geek moment didn't I? Lol.
  • n0ob
    n0ob Posts: 2,390 Member
    Aw...a flash back! But must say my preference is for quantum mechanics. ;)

    ETA...I just had a total geek moment didn't I? Lol.

    I liked organic myself. In 2nd semester I had a 96 average when a 72 avg. got an A. I was not well liked by students outside my group in that class...
  • snoopytwins
    snoopytwins Posts: 1,759 Member
    Aw...a flash back! But must say my preference is for quantum mechanics. ;)

    ETA...I just had a total geek moment didn't I? Lol.

    I liked organic myself. In 2nd semester I had a 96 average when a 72 avg. got an A. I was not well liked by students outside my group in that class...
    Well hello! Lol. I did my undergraduate thesis in bio-organic chemistry. You love me now don't you?
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