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Homework Help: Basic Mole Concept Questions, Grade 11 Chem

  1. Mar 25, 2008 #1
    Hey guys, i'm back, finished my term in physics with a 96% final grade, thanks to all you guys.

    So i thought id try you guys before i went to find a chemistry help forum.

    I get the Mole Concept, kinda, heres an example question (i got an answer, not sure if its right, we don't get a "back of the book" for chemistry. But its a great question to base my issues upon.

    If 1.0L of nitrogen gas reacts with 3.0 L of chlorine gas when both gases are at the same room temperature and pressure, how many chlorine molecules are present for every molecule of nitrogen in the reaction? Suggest a formula for the compound formed and name the compound.

    Alright, first of all, the mole concept illustrates that in a reaction, the amount of particles will always remain the same, or something close to that (ending spring break, trying to remember everything.) so i assumed their would me 3 molecules of chlorine, for every molecule of nitrogen, if it reacted with no leftovers, which i'm assuming.. would that be correct?

    So that was my answer, suggest formula was: [tex]ClN_3[/tex] Chlorine trinitride?? is that correct? and does it matter, if it was the otherway around, trinitrogen monochloride?

    Another question on the mole concept,. is how does it relate to grams? the atomic mass unit, for example 69.7u, refers to the unique mass in relation to hydrogen right? As it is 69.7 times heavier than H, (btw, im using Gallium for this example) that would also mean its 69.7grams/1mol Ga, how does it even relate to grams, grams is such a large unit for an amount of substance for an element. Does anyone have any further reading on the mole concept that would be good for a gr 11 highschool student.
  2. jcsd
  3. Mar 25, 2008 #2
    I would think the formula name is trinitrogen monochloride since the chlorine atom has the lower oxidation state.

    As for the mole concept: 1 mole is equal to 6.02 x 10^23 particles (either atoms or molecules depending on what you're working with), which means that for Ga, the combined weight of 6.02 x 10^23 atoms is equal to 69.7 grams. So how much does a single Ga atom weigh? 1 / (6.02 x 10^23 / 69.7 g ) = 1.158 x 10^-22 g, or in other words, 69.7 atomic mass units. From this, you can calculate the weight of one atomic mass unit to be 1.66 x 10^-24 g.
    Last edited: Mar 25, 2008
  4. Mar 25, 2008 #3
    ahh that would make sense, so someone just measured how many particles of hydrogen is in one gram of hydrogen, and made the amount of particles, 1 mol, and based the rest of the periodic table off of that?

    I'm not sure we've learnt about oxidation states yet, ill refer that to my teacher, thanks Snazzy!
  5. Mar 25, 2008 #4
    and i was right abuot the number of chlorine particles to nitrogen particles?
  6. Mar 25, 2008 #5
    Actually, someone used carbon-12 in its unbound and ground state to measure how many atoms there were in exactly 12 grams of carbon and everything was relative to that.
  7. Mar 25, 2008 #6
    wow thats really interesting, i greatly appreciate all the help.

    EDIT: i thought someone measured the mass of hydrogen, because it was the lightest element, and declared that a value of 1.0, and measured the rest of the periodic tables elements atomic mass units in relation to how much heavier it was than hydrogen??
  8. Mar 26, 2008 #7

    ??? Perhaps NCl3---nitrogen trichloride?
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