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Homework Help: Stoichiometry problem

  1. Nov 14, 2005 #1
    Im taking an organic chemistry lab, must calculate the following:

    NaBH4 is normally prepared for use in basic aqueous solution. Calculate the mass of a 12% NaBH4 aqueous solution required theoretically to reduce 5.00 g of acetophenone.

    I am can probably have a go at this question if I can get a hint on how to start ? Anyone point me in the right direction, I dont want the solution but a helping hand in working out the right way to do this. Thanks in advance.

    Edit: 12 moles NaBH4 / 100 mL water ? x 1 mole NaBH4 / 38 g NaBH4 x ... ?
    Last edited: Nov 14, 2005
  2. jcsd
  3. Nov 14, 2005 #2


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    Staff Emeritus
    Science Advisor

    Is that 12% NaBH4, 12% by weight (mass)? Then it would be 12 g NaBH4 in 100 gm of solution. Then one must convert that to moles.

    See - http://environmentalchemistry.com/yogi/chemistry/MolarityMolalityNormality.html

    Another example -
  4. Nov 14, 2005 #3
    NaBH4 by mass ...partial solution

    Calculated Molecular Weight
    MW NaBH4 : 23 + 11 + 4 = 38g

    Convert to moles - NaBH4
    12g NaBH4 / 100g NaBH4 * 1 mole NaBH4 / 38g = 0.0032 moles NaBH4

    However, at this point I need to write a balanced equation for the Acetophenone and NaBH4 reactants ? Im not sure if this makes sense so far.

    Any hints ?
    Last edited: Nov 14, 2005
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