Question

#24

read B. Titration of an unknown acid sample (treat as “HA" for reactions) 21. Obtain an unknown sample of a monoprotic acid (HA) and record the unknown number. You will be given a sample of the acid that will allow for more than one titration if neede however, this is all you will get - so be careful with it! Perform a pH-monitored titration of a 25.00 mL sample of your acid A. Record the plH of the weak acid solution before the titration begins. Record the starting 22. volume on the buret B. Add approximately 0.50 ml of the NaoOH solution. Record the precise volume. Turn off the stirrer. Record the pH. C. Repeat step 22.B. for three additional 0.50-mL aliquots. D. Add approximately 2.00 mL of the NaOlI solution. Record the precise volume. Turn off the stirrer. Record the pH. E. Repeat step 22.D., recording the precise volume and pH at each interval of base added. Continue adding 2.00-mL. aliquots of base until the pH in the solution is ~ 1.8 pH units above what it was at the end of part 22.C. Then, begin adding the NaOH solution in 1- drop increments (about 0.05 mL). Carefully record the precise volume and pH at cach increment F. When the pH~ 10, begin adding the NaOH solution in 2-mL aliquots. Add six 2-mL aliquots, recording the precise volume and pH after each. 23. Plot the pH versus volume of NaOH solution for this pH-monitored titration. Graphically determine the equivalence point and the pKa. Calculate the concentration of the unknown acid solution and the Ka Based on the Ka of the acid, determine its identity. Calculate a percent error based on this assignment (compare Ka's for the percent er 24. 25. ror) 2-0omnhl 5.33 unknowns anple#s, 2/ 6 @After 0.5m fterfera.o Ph:9.30 P1 2.97 Start vol: wans2L PH: 3.33 NabH Starr: 0mL PH: 3.83 hia vol:lmL Aterzo on fter o.smu. (e) After 2. 0 m u P144 Vol: 12m calhe

Answer 1