Acid / base titration

 

background [prelab assignment (15 points) due at the beginning of the lab]

1. define "equivalence point" using calculus concept(s)

2. define "end point"

3. explore Excel based titration curve simulation; simulate add 0.01 M strong base with a single hydroxide to 20 mL 0.005 M strong monoprotic acid (select appropriate choices from drop down menus; pH indicator macros don't work) review pH probe calibration video: Xplorer (or Spark) BEFORE lab (ipod download available, i.e. *.m4v file, which may be used during lab)

purpose

compare the determination of [HCl] using

materials

buret; ring stand with buret holder

beaker, pH meter, bromothymol blue

solid NaOH, water, balance, graduated cylinder

aqueous solution of HCl [unknown concentration]

 

methods [delegate lab work]

prepare 0.4 M NaOH solution

rinse buret with water, then rinse with NaOH solution prior to use; fill with NaOH solution

use the above solution to determine the unknown [HCl] solution (~30 mL); add pH indicator until get a distinct color

do titration

discard chemical waste and clean / rinse all glassware

use / calibration of probe device  [see vodcast; iPod download available]

  1. turn-on Xplorer data collection device
  2. insert pH probe into pH transducer, which is inserted into the Xplorer 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
  12. DO NOT PRESS ANY OTHER BUTTON DURING YOUR MEASUREMENT
  13. 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 [25 points]

data analysis

data table

calculations - determine [NaOH]

titration curve & corresponding plot of its first derivative

determination of [HCl] based on the end point and versus equivalence point

statistical analysis  & conclusion