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Difficult question

  1. May 22, 2005 #1
    I'm having trouble with a question and I'm almost too embarassed to ask! I;ve spent the last couple hours trying to figure it out though and am getting nowhere fast.

    Liquid ammonia and ammonium nitrate, based on percentage of nitrogen by mass, which of these 2 would be the better fertilizer.

    Ammonium Nitrate - NH4No3
    Liquid Ammonia - NH3 ??

    Where do I start? I did something and got ammonium nitrate as having 35% N, 5% H and 60% O.
  2. jcsd
  3. May 23, 2005 #2
    This one is now going to use percentage masses (as you know) which is what I think would have been better in the other question you did. So now you are going to learn it.

    You have the molecular formulae and you can, therefore, work out the molar masses of each. You then need to write out each of the elements in the compound seperately and find there relative atomic mass (which you must know to have found the molar mass). Simple apply the way you work out a percentage to each of the elements and you can find which will have the most.

    This may have been what you did but you have not put any workings down so I have assumed you almost guessed the answers. A word of caution: make sure you write what you have done, no matter how silly, so we can see where you are going right/wrong and can help you to proceed.

    The Bob (2004 ©)

    I know you may say this is really small but it is important.

    You either have to change the N in No3 to a M (for molybdenum) or you need to make the o in No3 a large, capital O so it represents oxygen i.e. NH4NO3.
    Last edited: May 23, 2005
  4. May 23, 2005 #3
    If you're going by mass, you shouldn't have to do any calculations (Assuming you know what the mass of hydrogen relative to nitrogen is)
  5. May 23, 2005 #4


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    Well start by observing that

    [tex]total~mass~of~nitrogen~in~the~molecule/total~mass~of~molecule[/tex] is the percentage, you can multiply by 100, but it isn't necessary.

    Start by calculating everything in terms of a mole basis...say you have one mole of each compound and go from there. Show us what you can do.
  6. May 31, 2005 #5
    Not small at all! Thank you for pointing that out :)
  7. May 31, 2005 #6
    So....(is this correct?)

    Molar Mass of Ammonia (liquid): NH3 – 14.0 + (1.0*3) = 17 Amount of Nitrate: 14/17 (82%)
    Molar Mass of Ammonium Nitrate: NH4NO3 14.0+(1.0*4)+14.0+(16.0*3): =80 Amount of Nitrate: 28/80 (35%)

    Liquid Ammonia has a higher percentage of nitrate and so would be the better fertilizer.
  8. May 31, 2005 #7


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    Your answer seems to be correct however, you could have easily deduced the answer simply by observing the formula, and making a educated estimation.
  9. May 31, 2005 #8


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    Staff: Mentor

    ...higher percentage of nitrogen...

    Chemical calculators at
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