Chemistry
posted by Dexter .
Hi there  I'm going to post the question as written in my book.
Three 20.0 mL samples of nitric acid are titrated with a 0.200 mol/L solution of sodium hydroxide. The results for the three trials are shown in the table below. What is the concentration of the hydrochloric acid?
Trial  1  2  3  average
_______________________________________
Final Burette   
reading (ml) 28.2027.9028.00
_______________________________________
Initial Buret50.0 50.0 50.0 
te reading(ml)
_______________________________________
Volume of
NaOH added    
_______________________________________
end of question in book
my dilema:
Right off the bat I'm confused because I get a negative number for the volume added. ie. 28.20 ml  50 ml = 21.80 ml which can't be right.
From there the rest of my answer is based on the negative number which I don't think is right. Please help me clarify how to work out the volume of the NaOH added if the final burette reading is 28.20 ml and initial burette reading is 50 ml. From there I think I can manage the rest but will probably request you verify
Thanks in advance!!!

I'm confused also. Perhaps the buret is calibrated with 50.0 at the top and zero at the bottom so you have added 5028.2 = 21.8 mL. However I've never seen a buret calibrated that way. Furthermore, it doesn't make any sense to calibrate it in reverse. It makes more sense for those 50.0 mL initial readings to be 0.50 or 0.05 or something like that.

That's what I thought....Thank you !!!

Experiment:determine the normaliyy and normality and strength of the given solution of sodium hydroxide provided n/10 hcl general calcutions normality and strength intial reading is 3 S.no is 0 and the final reading is 9,9.4 9.5 and volume of hcl used ?