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chemistry

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The initial concentration for the compounds involved in the reaction displayed were determined to be [CH4(g)] = 0.9530 mol/L, [H2O(g)] = 0.9911 mol/L, [CO(g)] = 0.7474 mol/L, [H2(g)] = 0.2717 mol/L. Calculate the value of the equilibrium constant (Kc) at 1200 K if the equilibrium concentration of CO(g) was 0.8584 mol/L.

CH4(g)+H2O(g) = CO(g)+3H2(g)

i know to find Kc you have to do the products over reactants like this:

([H2]^3)([CO]) / ([CH4][H2O])
and i did the difference of 0.854 & 0.7474 for CO to get it but the answer is still not right..
the answer is 0.2561
but i keep getting 0.0158
i dono what im doing wrong..

**thanks for the help btw!!!

  • chemistry -

    Your 0.0158 is not Kc because you have substituted the INITIAL concns. You are supposed to substitute equilibrium concns. I would look at this way.
    ........CH4 + H2O ==> ..CO +.... 3H2
    init..0.9530..0.9911..0.7474...0.2717
    change....-x.....-x.......+x.....+3x
    eq.0.9530-x..0.9911-x..0.8584.0.2717+3x

    So you get x by 0.8584-0.7474 = 0.1110
    which allows you to find all of the other equilibrium concns. Substitute those to obtain Kc.

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