TIPS

Virtual Lab 8b

Chem 1403

 

 

This is the tough one, because you do not know the molar mass of the unknown monoprotic acid.  The first thing you need to do is determine how much acid you want to work with, and that not only depends on its molar mass, but the concentration of the base you are using to neutralize it.  So you must explore, that is, consider a given quantity of base, say 25 mL of 0.100M NaOH.  If two students have different acids with different molar masses, the one who has the larger molar mass will need more of the acid to neutralize the base. 

 

I suggest you look at this from the other side, and instead of asking, how much base do I need to neutralize a given quantity of acid, ask, how much acid do I need to neutralize a given quantity of base.  That is, start of with 25 mL of base, and find out how much acid this will neutralize.  Once you know that, use that quantity of solid acid in your titration (first diluting with water), and proceed to titrate with a base. 

 

Note: many solid acids are organic compounds and have limited solubilities in water.  You need to use a quantity that is small enough to completely dissolve in the amount of water you add (and yet leave enough room in the flask to add the base once you start the experiment).  Now, if you use the virtual lab in "precise mode", you can add any quantity of base, that is, 0.00001 mL of 1M.  So, you are not confined by the precision of your instruments in the design of your experiment. 

 

Tip: You can answer these questions with just two measurements.  You do not need to make a complete titration curve, you only need two points off the curve.