Acid / base titration


background [prelab assignment (25 points) due at the beginning of the lab]

This laboratory activity is based on investigation 4 in your AP chemistry lab manual; thus, it provides some relevant background for the following prelab questions and this laboratory activity. While investigation 4 analyzes fruit juices, you will be analyzing an aqueous solution of a strong acid (HCl) and strong base (NaOH).


using a 0.5 M NaOH solution, standardize a HCl solution, then use the HCl solution to determine the concentration of an unknown NaOH solution

compare the determination of the unknown [NaOH] [HCl]using the equivalence point ( i.e. find the inflection point using your calculus background) versus end point (i.e. pH indicator color change)


buret; ring stand with buret holder, 100 mL volumetric flask

beaker, pH meter, bromothymol blue

~ 0.5 M NaOH (prepared by YOU);  unknown [HCl] & [ NaOH]

2 aqueous solution of HCl & NaOH [unknown concentrations]


methods [delegate lab work]

rinse buret with solution (acid or base) prior to use

use the above solution to determine the concentration of the unknown [HCl] & [NaOH] solutions (~50 mL)

use / calibration of probe device - record the experimental protocol in your lab notebook, since you will use the pH probe in a subsequent lab

  1. insert pH probe into pH transducer, which is inserted into the Xplorer device
  2. turn-on Xplorer data collection device
  3. rinse pH electrode with water prior to entry into any solution - to prevent contamination between solutions
  4. press display button until the calibration screen appears
  5. press the check button
  6. press the tab button - to move among sign / digits
  7. press - or + button, as needed, to change sign / digits - to be adjusted to reflect pH of buffer
  8. put pH probe into buffer & swirl for at least 15 seconds [to ensure good contact between pH probe & buffer]
  9. press the check button
  10. repeat steps 6-9 for second buffer
  11. press display button; should see pH of solution
  12. press start / stop; wait ~ 10 seconds; press start / stop (to "save" calibration)
  13. press display button until the pH screen reappears
  15. the probe has being calibrated and is now ready for use; with about a minute of inactivity the probe will automatically power-down; simply turn it back on.

data analysis

student design


Content of lab report [35 points]

data analysis (15 points)

determine [HCl]

determine [NaOH]

statistical analysis (include interpretation of p-value) of class data  &  conclusion

questions  (20 points)

basis of selecting a pH indictator 

specify / justify a pH indicator you could use in this titration (except bromothymol blue) and an indicator that you should not use in this titration (hint: figure 16.4 in your textbook). 

error analysis - refers to postlab assesssment in investigation 4 in the AP chemistry lab manual

# 1, 2, 4


example of titration protocol

lab activity source (examples):  site 1  & site 2 [access 4 / 2009]