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What volume of the gas absorbed by the alkali ?

  1. Feb 21, 2007 #1
    1. The problem statement, all variables and given/known data

    A mixture of 10cm^3 of methane and 10cm^3 of ethane was sparked with an excess oxygen . After cooling to room temperature , the residual gas was passed through aqueous potassium hydroxide

    What volume of the gas absorbed by the alkali ?
    2. Relevant equations

    N/A

    3. The attempt at a solution
    I have no idea for the solution . Any hint ?
     
  2. jcsd
  3. Feb 21, 2007 #2
    what are the results of 'sparking' methane and ethane with oxygen? i.e. what are the products of combustion?
     
  4. Feb 21, 2007 #3
    Water and carbon dioxide . I think . So..?
     
  5. Feb 21, 2007 #4

    Gokul43201

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    And what kind of gas is carbon dioxide? What happens when you pass such a gas through an alkaline solution like KOH?
     
  6. Feb 21, 2007 #5

    I have no idea . Guide pls .
     
  7. Feb 21, 2007 #6

    Gokul43201

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    KOH is a base. What do bases (or basic/alkaline solutions) react with?
     
  8. Feb 21, 2007 #7
    I only know that acid react with base will produce water and salt .
     
  9. Feb 21, 2007 #8

    Gokul43201

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    Good, then keep in mind that CO2 is an acidic oxide. It is something like an acid, minus the water. It too, will react with a base, forming a salt. The point of this is to recognize that when you pass a gaseous mixture containing CO2 through a solution of KOH, all (or a very large part of) the CO2 will be removed by this reaction.

    Write down and balance the equations for the combustion of ethane and methane. How much CO2 is produced from the given quantities?
     
    Last edited: Feb 21, 2007
  10. Feb 21, 2007 #9
    I think the equation is as below :

    For methane combustion :
    CH4 + O2 ---> CO2 + H2O
    Since 1 mole of CH4 : 1 mole of CO2
    SO: 10CM^3 CH4 will gives 10 cm^3 CO2

    For ethane combustion :
    C2H6 + O2 ---> CO2 + H2O
    Since 1 mole of C2H6 : 1 mole of CO2
    So: 10cm^3 C2H6 will gives 20 cm^3 CO2


    Total gas has absorbed is 30 cm^3 ?
    Am I correct ?
     
    Last edited: Feb 21, 2007
  11. Feb 21, 2007 #10

    Gokul43201

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    You have not balanced the equations. You need to do that before you determine the mole ratios.
     
  12. Feb 21, 2007 #11

    {EDIT}
    For methane combustion :
    CH4 + 3O2 ---> CO2 + 2H2O
    Since 1 mole of CH4 : 1 mole of CO2
    SO: 10CM^3 CH4 will gives 10 cm^3 CO2

    For ethane combustion :
    C2H6 + 7/2O2 ---> 2CO2 + 3H2O
    Since 1 mole of C2H6 : 2 mole of CO2
    So: 10cm^3 C2H6 will gives 20 cm^3 CO2 ?

    so
    total volume is 30cm^3 ?
     
  13. Feb 21, 2007 #12

    Gokul43201

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    Looks good.
     
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