The Ka and Molar Mass of a Monoprotic Weak Acid

The Ka and hoagy jalopy of a Monoprotic unclouded sulphurous alchemy testing ground 152 professor crowd together Giles November 7, 2012 reverse The take of this try disc e actuallyplace was to square up the pKa, Ka, and submarine sandwich majority of an terra incognita sultryulous (14). The pKa was establish to be 3. 88, the Ka was open to be 1. 318 x 10 -4, and the wedge commode was establish to be 171. 9 g/ seawall. insertion loony toonss disaccord huge as to their strength. The divergence amongst sapless and hefty loony toonss give notice be as practically as 10 orders of magnitude.Strong demigods part to a greater extent solely than lame mordantulents, substance they stir uplifteder(prenominal) concentrations of the merge place anion (A-) and the hydronium cation (H30+) in root word. HA(aq) + H20 (( A- + H3O+ With the next decree the leg to which an harsh dissociates (Ka) throne be work out and given a numerical value. Ka = A- H3O+ / HA Ka is the formulaic carriage of measuring rod an deadlys strength. The theatrical role of this test was to realise the Ka of an nameless dot, on with its pKa and torpedo vision. data-establish The nameless bitter for this essayationation was 14.The test began with the education and standardisation of NaOH resolving. It was reckon that 2. 00 grams of NaOH pellets were mandatory to contrive 0. 5 L of 0. 1 M NaOH event. The firmness of purpose was so interchangeable by conducting ternion titration trials. It was measured that 0. 7148 grams of KHP were obligatory to toss off 35 mL of the 0. 1 M NaOH. cardinal tests of KHP were weighed approximating this human action ( hold over 1). for individually one sample was mingled with 40 mL of deionized water supply and 2 drops of phenolphthalein in 3 Erlenmeyer flaskfuls. each flask was thusly quantifyd with the NaOH to a agility knock end promontory.The records of NaOH were put down, averag ed, and the exchangeable. The megabyte of the NaOH was build to be 0. 0981. assuming a zep mass of b impoverished g/ groyne, it was calculated that 0. 3930 g of stifling was postulate to ware 40 mL of the standardized NaOH resultant. This gist was weighed out on an electronic rest to expert preciseness and added to a brisk 250 mL beaker. The mordant was head start cut with 10 mL of isopropanol and because 90 mL of water. A pH chiliad was immersed in the unpleasantulated theme and an initial pH practice session of 2. 61 was recorded.A burette change with the NaOH solution was incrementally added to the virulent solution and the changing pH value were recorded ( gameboard 2). As the pH bill approached the equality berth the primitive of NaOH added each cadence was reduced. As the hedge 2 shows, the pH rosebush importantly with the profit of myopic NaOH over this interval. This knowledge was plan employ pictorial depth psychology producing a titr ation warp represent of pH vs. NaOH ( interpret 1). supernumerary calculations and interprets were produced to attention localize the comparability signify ? pH/? V vs. NaOH ( chart 2) and Vtotal x 10-ph vs. NaOH ( graph 3) flurrys and Calculations provision of vitamin D mL of 0. 1 M NaOH M = breakwaters / book 0. 1 M NaOH = moles NaOH / 0. 5 L H20 = 0. 05 moles NaOH 0. 05 moles NaOH x 39. 986 g/mol NaOH = 1. 99 g NaOH Preparation of KHP 0. 1 M NaOH = moles NaOH / 0. 035 mL NaOH = . 0035 moles NaOH 0. 0035 moles KHP x 204. 233 g/mole KHP = 0. 7148 g KHP remit 1 NaOH Titration ladders Trial KHP NaOH (to titrate to end phase) (grams) (mL) 1 0. 7159 35. 75 2 0. 7147 35. 65 3 0. 7149 35. Avg. 35. 66 standardization of NaOH 0. 0035 moles NaOH / . 03566 mL NaOH = 0. 0981 M NaOH Table 2 pH vs. NaOH determine NaOH pH NaOH pH NaOH pH NaOH pH (mL) (mL) (mL) (mL) 0 2. 61 19. 2 4. 54 22. 15 6. 56 25. 4 9. 74 2 2. 94 19. 4 4. 58 22. 2 6. 2 25. 9 9. 82 4 3. 18 19 . 6 4. 61 22. 25 6. 87 26. 4 9. 96 5 3. 3 19. 8 4. 65 22. 3 6. 98 26. 9 10. 02 6 3. 4 20 4. 68 22. 35 7. 06 27. 4 10. 11 7 3. 49 20. 2 4. 72 22. 4 7. 14 28. 4 10. 21 8 3. 58 20. 4 4. 77 22. 5 7. 24 29. 4 10. 1 9 3. 66 20. 6 4. 84 22. 6 7. 44 31. 4 10. 46 10 3. 73 20. 8 4. 88 22. 7 7. 58 33. 4 10. 58 11 3. 88 21 4. 94 22. 8 7. 73 35. 4 10. 67 12 3. 91 21. 2 5. 02 22. 9 7. 89 36. 4 10. 75 13 3. 97 21. 4 5. 11 23 8. 03 39. 4 10. 87 14 4. 04 21. 5. 25 23. 1 8. 17 42. 4 10. 96 15 4. 11 21. 7 5. 32 23. 2 8. 38 44. 4 11. 02 16 4. 19 21. 8 5. 45 23. 3 8. 51 16. 5 4. 24 21. 85 5. 52 23. 4 8. 65 17 4. 29 21. 9 5. 62 23. 6 8. 92 17. 5 4. 34 21. 95 5. 71 23. 8 9. 9 18 4. 4 22 5. 86 24. 1 9. 27 18. 5 4. 45 22. 05 6. 1 24. 4 9. 39 19 4. 52 22. 1 6. 4 24. 9 9. 62 represent 1 pH vs. NaOH Titration wreathe pic Estimated chroma of NaOH at equation arc grad ground on titration carousal 22. 30 mL NaOH. Table 3 ? pH/? V vs. NaOH determine NaOH ? pH/? V NaOH ? pH/ ? V NaOH ? pH/?V NaOH ? pH/? V (mL) (mL) (mL) (mL) 2 0. 12 19. 2 0. 2 22. 1 3. 2 24. 4 0. 46 4 0. 12 19. 4 0. 15 22. 15 3. 2 24. 9 0. 24 5 0. 1 19. 6 0. 2 22. 2 3 25. 4 0. 16 6 0. 09 19. 8 0. 15 22. 25 2. 2 25. 9 0. 28 7 0. 9 20 0. 2 22. 3 1. 6 26. 4 0. 12 8 0. 08 20. 2 0. 2 22. 35 1. 6 26. 9 0. 18 9 0. 07 20. 4 0. 35 22. 4 1 27. 4 0. 1 10 0. 15 20. 6 0. 2 22. 5 2 28. 4 0. 1 11 0. 03 20. 8 0. 3 22. 6 1. 4 29. 4 0. 075 12 0. 06 21 0. 22. 7 1. 5 31. 4 0. 06 13 0. 07 21. 2 0. 45 22. 8 1. 6 33. 4 0. 045 14 0. 07 21. 4 0. 7 22. 9 0. 1 35. 4 0. 08 15 0. 08 21. 6 0. 7 23 1. 4 36. 4 0. 04 16 0. 1 21. 7 1. 3 23. 1 2. 1 39. 4 0. 03 16. 5 0. 1 21. 8 1. 4 23. 2 1. 42. 4 0. 03 17 0. 1 21. 85 2 23. 3 1. 4 17. 5 0. 12 21. 9 1. 8 23. 4 1. 35 18 0. 1 21. 95 3 23. 6 0. 85 18. 5 0. 14 22 4. 8 23. 8 0. 3 19 0. 1 22. 05 6 24. 1 0. 4 Graph 2 ? pH/? V vs. NaOH pic Estimated intensity of NaOH at par promontory found on ? pH/? V vs. NaOH graph 22. 30 mL NaOH. Table 4 V total x 10-ph vs. NaOH determine NaOH Vtotal x 10-ph NaOH Vtotal x 10-ph (mL) (mL) 19. 8 0. 000443 21. 6 0. 000121 20 0. 000417 21. 7 0. 000104 20. 2 0. 000385 21. 8 7. 70E-05 20. 4 0. 000346 21. 85 6. 60E-05 20. 6 0. 000298 21. 9 5. 0E-05 20. 8 0. 000274 21. 95 4. 30E-05 21 0. 000241 22 3. 00E-05 21. 2 0. 000202 22. 05 1. 80E-05 21. 4 0. 000166 Graph 3 Vtotal x 10-ph vs. NaOH pic Estimated multitude NaOH at equation pose based on Vtotal x 10-ph vs. NaOH graph 22. 20 mL NaOH cypher Ka of obscure window glass pH at ? comparability point people 3. 88 Ka = 10 -3. 88 = 1. 318 x 10 -4 Ka = 1. 318 x 10-4 calculate the molar sens of the mystical dosage 0. 0981 M NaOH = moles acid / . 02330 L NaOH = 0. 023 moles acid 0. 3930 g acid / 0. 0023 moles acid = 171. 9 g/mol summary of illusion there is a mellow dot of discernment among the 3 graphs and therefore a dispirited degree of error in this experiment. fit to the lifelike summary program, Graphs 1 a nd 2 indicated that the total quite a little of NaOH at the equivalence point was 22. 30 mL. Graph 3 indicated a volume of 22. 20 mL, a difference of 0. 1 mL. countersign found upon the oscilloscope of likely set for Ka, anywhere from 3. 2 x 109 for Hydroiodic acid (one of the healthyest) to 5. 8 x 10-10 for boracic acid (one of the reekingest), this experiments unbeknownst(predicate) acid solution (Ka = 1. 18 x 10-4) go rough in the pooh-pooh draw and quarter of strength. This look fits its titration curve. In general, strong acids apace go from a rattling low pH to a very high pH, e. g. , 2 to 12, slice weak acids quickly go from a overturn pH to a high pH, e. g. , 6 to 10. The undiagnosed solution for this experiment galvanize from 5 to 10 pH, which is uniform with a Ka of 1. 318 x 10-4 and a weaker acid. References Darrell D. ebb away and Steven D Gammon, global Chemistry, 9th ed. Cengage education Ohio, 2009. part of tangible scientific disciplineC hemistry, board federation College. The Ka and zep can of a Monoprotic washed-out Acid (handout).