[CHM 111] NaOH Writeup

[Andrew J. Pounds]

Gen Chem Students  -- we haven't covered solution stoichiometry yet in 
class (we start that Tuesday) but that shouldn't prevent you from doing 
the lab writeup and prelab for the NaOH and determination of KHP this 
week.   Here are some pointers to help you...

First -- and foremost -- the mass of KHP is not the mass of K plus the 
mass of H plus the mass of P.   KHP is an abbreviation for the compound 
named potassium hydrogen pthalate.  Make sure you use to correct molar 
mass when computing the moles of KHP used in each trial.   The structure 
of the compound is shown in the lab description.

Concentration is defined as the moles of solute per liter of solution.   
Technically this is the unit "molarity".    The KHP and NaOH react on a 
1:1 basis.  For that reason to find the molarity of your NaOH solution 
you will need to divide the moles of KHP by the volume of NaOH used (in 
Liters). Remember -- you tried to make something close to 0.13 molar -- 
so if you get something really different than this we may need to talk.  
Anyway, compute the molarity of your NaOH for all of your trials, and 
then take the average of your three GOOD trials.

The formula for average deviation is found in the description of the 
first lab where you measured the density of water and that of an unknown 
metal.  Using your three GOOD trials compute the average deviation.

*Make sure that you record all of **this in your lab notebook -- or 
somewhere that you will have access to it**-- because you will need your 
determined molarity to complete the **unknown KHP experiment you are 
doing this week.*


In the big box on the cover page please record the average molarity of 
your NaOH solution and the average deviation in your recorded value.


I am playing with the pre-labs, but will have the posted soon.


As always, let me know if you have questions.


-- 
Andrew J. Pounds, Ph.D.  (pounds_aj at mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627
http://faculty.mercer.edu/pounds_aj

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