1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Stoiciometry. Finding mass and formula

  1. Oct 9, 2006 #1
    PROBLEM:
    0.20 moles of C?H?N? + 60,7 g O2 --> 35,2 g CO2 + 25,2 g H2O + ? g NO2

    how many grams of the molecule C?H?N? did we have before the reaction?

    Find the forumla.

    ANSWER:
    18,1g, C4H14N2

    BUT:
    how do you solve it?

    Thanks in advance!
     
  2. jcsd
  3. Oct 9, 2006 #2
    Try it mathematically. Start by making everything in the same units, e.g. all in moles. Then compare the coefficents of each compound that contains the same element, e.g. Equate the carbons - 0.2 Cx = 0.8 C. Then think about elements and how they work, e.g. if you have 2CO2 this is the same as saying there are 2 carbon atoms and 4 oxygen atoms or C2O4. Obvious the mole contains more than just one molecule of a substance, which is what I am implying, but it will allow you to make this relationship that will help you to solve the problem. If it really gets to you, say that 2 moles of CO2 is the same as 1 mole of C2O4.

    From the equation, I originally wrote, x = 4, which is the number of carbon atoms you need per mole (as per your solutions), as 0.8 C = 0.2 Cx = 0.2x C (if we use the logic from earlier).

    Hope this helps with the solution, not necessarily the chemistry.

    The Bob (2004 ©)

    P.S. I reckon the mass of NO2 is 18.3g not 18.1g :biggrin:
     
    Last edited: Oct 9, 2006
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Stoiciometry. Finding mass and formula
  1. Finding the mass (Replies: 11)

Loading...