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Simple Basic Chemistry Problem

  1. Sep 12, 2008 #1
    1. The problem statement, all variables and given/known data
    Given a table of percentages. One column stands for the percent of Nitrogen in a substance, the other a percent of Oxygen. Given the table (4 rows with different values), figure out the ratio of atoms of Oxygen for a given amount of Nitrogen.

    2. Relevant equations

    3. The attempt at a solution

    I have no idea how to even go about doing it. I tried plugging in the weights of the elements, i tried ignoring them. I tried this problem a few different ways but honestly, i haven no idea how to even approach it, i cant seem to figure it out.

    It's from the first chapter of our chemistry book, i've tried reading the book, but they dont mention nor show a sample of how to do a problem like this. Nor did the professor do a sample problem in class. I have no idea how to approach this problem, i know it's a simple solution but i havent taken chemistry in about 3 years, so i'm completely lost here.

  2. jcsd
  3. Sep 12, 2008 #2


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    Staff: Mentor

    Water contains 11.19% of hydrogen and 88.81% of oxygen. Let's assume we have 100 g of water - we have 11.19 g of hydrogen and 88.81 g of oxygen then. That means we have 11.19/1.01=11.08 moles of hydrogen and 88.81/16.00=5.55 moles of oxygen. There is exactly 11.08/5.55=2.00 moles of hydrogen per mole of oxygen, so water must have formula H2O.

    Can you do the same to your nitrogen question?

    In general you don't have to assume 100 g of substance, but it quite often simplifies thinking.
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