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? asked in Science & MathematicsChemistry · 8 years ago

What volume of oxygen gas at 25c and 1.06 atm is needes to completely combust 5.41g of propane?

Chemical equation

C3H8 + O2 -> CO2 + H2O

Answer has to be in liters. I got 2.83, but it was not right.

1 Answer

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  • KennyB
    Lv 7
    8 years ago
    Favorite Answer

    First, balance the equation:

    C3H8 + 7O2 --> 3CO2 + 4H2O

    Now, find moles -- divide 5.41 g of propane by the molecular weight of propane to find moles of propane.

    I get 0.123 but you will need to use at least three significant figures in the molecular weight.

    Multiply this by 7 to find moles of O2

    Now, how much volume does this occupy?

    V = nRT/P

    where

    n = answer for O2 above

    P = 1.06 atm

    T = 298 K

    and R is in units of L-atm/deg-mol. (This is 0.08206)

    Solve for V

    I get 19.9 L

    As best I can tell, you forgot to account for the 7:1 ratio of oxygen to propane

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