Limiting Reagents and Yields?

Im doing this lab and I need some help with the theoretical yield. Its pretty much a hypochlorite oxidation of benzoic acid by the haloform reaction. Which is the limiting reagent? Would there be two theoretical yields since there is two products? Here are the properties of the reactants:

-Acetophenone: MW=120.16 Amount=20uL Density=1.03

-NaOCl (used in excess): MW=74.44 Amount=700uL Density=1.07

-Sodium Sulfite: MW=120.6 Amount=5mg Density=1.36

1 Answer

  • 1 decade ago
    Favorite Answer

    Let UNITs guide you; always USE THEM in your calculation to prevent errors

    Firstly, the eqn:

    PhC=OCH3 + 4NaClO ----> PhC=OOH + 4NaCl + H2CO3

    ____2NaClO * Na2SO3 ----> 2NaCl + Na2SO4

    sum eqns

    PhC=OCH3 + 6NaClO + Na2SO3 ---> PhC=OOH + 6NaCl + H2CO3 + Na2SO4

    mmoles PhC=OCh3 = 0.020ml * 1030 mg/ml / MW PhC=OCH3 mg/mmole = ??

    mmoles NaClO = 0.700ml * 1070mg/ml / MW NaClO mg/mmole = ??

    mmoles Na2SO4 = 5mg / MW Na2SO4 mg/mmole = ??

    ratio by eqn:____ 1 / 6 / 1 for PhC=OCH3 / 6NaClO / Na2SO3

    ratio by reactants: 1 / (mmoles NaClO/mmoles PhC=OCH3) / (mmoles Na2SO4/mmoles PhC=OCH3)

    yield mg PhC=OOH = mmoles PhC=OCH3 * MW PhC=OOH mg/mmole

    Plug and SOLVE (for PhC=OCH3 conversion, it is the limiting reactant as there is plenty of NaClO to oxidize both)

    Basic mathematics is a prerequisite to chemistry – I just try to help you with the methodology of solving the problem.

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