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!

The combustion of petrol can be approximately represented by the

  1. Jun 13, 2010 #1
    The combustion of petrol can be approximately represented by the equation

    2C8H18(g) + 25O2 -----> 16CO2 + 18H2O

    The density of Ocatane is 0.7 gcm(cubed)

    What mass of oxygen is used up when 1L of petrol is burnt in a car engine?

    ATTEMPT

    0.7 gcm[tex]^{}-3[/tex] = 0.0007 gL[tex]^{}-1[/tex]
    Therefore
    density = mass/volume
    0.0007 gL[tex]^{}-1[/tex] = mass / 1 L
    0.0007g = mass

    amount (of petrol) = mass/molar mass
    = 0.0007/228
    = 0.000003 mols

    therefore...amount of oxygen is 25 times amount i got for petrol?
    so
    n(o) = 0.000003*25
    then
    0.000075 = mass/molar mass
    0.000075 = mass/32
    0.0024g = mass


    Have i blown it somewhere? Im not sure about the mols thing i did when going from petrol to oxygen... I mean do you times it by 25 OR 12.5 because the mol ratio is 2petrol + 25Oxygen
    i think times by 25 because when finding molar mass for petrol I multiplied everything by 2

    btw the right answer is appparentlyyyy 2.5*10^3 grams, what did i do? ahh
    cheers
     
  2. jcsd
  3. Jun 14, 2010 #2

    Borek

    User Avatar

    Staff: Mentor

    Re: stoichiometry

    Mass of 1L is not 0.0007g.

    Please use [noparse]cm3[/noparse] tags for cm3 and [noparse]H2[/noparse] for H2.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: The combustion of petrol can be approximately represented by the
  1. Heat of Combustion (Replies: 1)

  2. Heat in Combustion (Replies: 1)

  3. Combustion reaction (Replies: 10)

  4. Heat of combustion (Replies: 1)

  5. Combustion Reactions (Replies: 6)

Loading...