All strang bases are hydraxidea wo they contain OH ions. Acids are proton donon ao they donate H- lons. Whien a strong LNTROBUCTION. base is mixed with an acid, the follawing net ionic raction occurs OH(aq)+H(aq)H2O(i) Sance water is acwiral, this is also calked a neutralitarion meacim. This reaction is alio quantitative so if only one of the concentradont (molanty) is known, the other may be determined by adding the 2 selutions until the number of moles of OH - ions equals the number of males or H - ions in the solution. Ia onder to decermine when this cocurs, a visual indicator is used. The indicator will change colors when the number of moles of OH ions equals the number of moles of H - ions in the solution. MATERJALS Ats hind wisp - twhid towp EXPERLMENT DPROCEDURES: CNITIAR VOLUMESAREFOR25 ML AUREITES. DQUBLTIFSO. ML RURETTESAREUSETZ. 1. Dispense 30ml of a solution of NaOH of known concentration into 1 tlask 2. Dispense 30ml of a solution of HCl of unknown concentration into a second hask: 3. Set up a ring stand with two burettes. Use a few mls of distilled water to make sure that the burettes do not leak. 4. Rinse and fill one burette with the NaOH solution. Do the same for the other burette using the HCl solution. 5. Mark down the level on each burette to 2 decimal places ( V zeaz. Vinid. Ning =254+20+ct a. Noce, buretes are calibrated to dispense. So when full, the burette will tead 0.00 . After say 18.50ml has been transferred from the burette to your reaction flask, the burette will read 18.50ml. b. Since you are always measuring relative to a start point, you may add any amount of solution to the burette as long as you stay in the marked calibrated region (for example, it's fine for you fill the burette to the 0.80ml mark: you will write Viass =0.80mlt) c. Do not EVER let the fluid in the burette go below the marked values. d. Do not EVER fill the fluid in the burette to a level above the marked values. 6. Put the 3 Er Erlenmcyer flask on the stir plate. Add the stir bar. This is your sample Alask. 7. Dispense 10.0ml of acid from your acid burette into the sample flask. 8. Add 2-3 drops of phenolphthalein indicator (please put the dropper bottle right back when you are done) and stir the solution. The solution will remain clear. 9. Place a whire sheet of paper under the sample flask (this will help you 5ce the endpoint) 0. Gradually add (titrate) the base solution from the base burette until the color just turns color to a faint pink. If your solution turns bright pink add cnough acid to bring it back to clear and very slowly add the acid until 1 drop causes a change in color. HCL 10.2042.130NGOA 11. Record the final readings on both burettes ( V2ad,V2hhus ). You have now completed your first titration. 12. Add 5.0ml of acid from your acid burette into the sample flask. The solution will return to clear. 13. Repeat the titration (step 10) until the solution is once again a faint pink color. 14. Record the final readings on both burettes ( V3x+d,Vsbase). You have now completed your 2nd titration. 15. Calculate the concentration of the HCl based on each titration result (sec calculations section). If the values are within 5%, proceed to Experiment 2. If not, you'll need to repeat this titration once again. At this point, the burettes will be low on material so you will need to refill both burettes, mark down the new starting volumes and then continue from step 12. EXPERIMENT 2 PROCEDURES: 1. The NaOH solution is no longer needed. Pour the remaining solution into the appropriate waste container. 2. Rinse the burette, your sample and your base Erlenmeyer flasks with water. 3. Rinse the base Erlenmeyer flask with a little sodium tetraborate and then add 30.0ml of sodium tetraborate to the flask: 4. Rinse and then fill the burette with sodium tetraborate (Na2B4O7 or borax). 5. Refill the acid burette. Now you have a burette full of acid and one full of sodium tetraborate. 7. Dispense 10.0ml of sodium tetraborate from your burette into the sample flask. 8. Add 2-3 drops of methyl orange indicator The solution will start out orange and turn red. 9. Place a white sheet of paper under the sample flask (this will help you see the endpoint) 10. Gradually add (titrate) the acid solution from the acid burette until the color just turns color to red. 11. Record the final readings on both burettes (V2b,900cid,V2blBocai). 12. Dispense 5.0ml of sodium tetraborate from your burette into the sample flask (orange again). 13. Repeat the titration (step 10) until the solution is once again a red color. 14. Record the final readings on both burettes (V3baccid,V3bBocax).41.05,15.09 15. Calculate the concentration of the sodium tetraborate based on each titration result (see calculations section). If the va are within 5%, you are done