# Stoichiometry problem

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 ... ?

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Astronuc
Staff Emeritus
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.

Percent by weight: To make up a solution based on percentage by weight, one would simply determine what percentage was desired (for example, a 20% by weight aqueous solution of sodium chloride) and the total quantity to be prepared.
See - http://environmentalchemistry.com/yogi/chemistry/MolarityMolalityNormality.html

Another example -

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 ?

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