 We're going to do a titration of solid sodium carbonate with a solution of hydrochloric acid to generate a titration curve for a polybasic compound. We're going to dissolve a known mass of sodium carbonate. We're going to pipette 50.00 milliliters of water into the beaker. We're going to stir it to dissolve the sodium carbonate. You know the number of grams of sodium carbonate, so you can figure out the number of moles of sodium carbonate. You know the molarity of the HCl that you're titrating with. You should calculate what the equivalence point volume is, so you can calculate the half equivalence point, the equivalence point, one and a half equivalence point, and the second equivalence point. You want to include those volumes in the data during your collection. Half equivalence point, first equivalence point, second half equivalence point, second equivalence point. We're going to place a calibrated pH electrode into the solution. We're going to be careful not to let the stir bar hit the electrode. We're going to use two indicators in this titration. The first indicator is going to be phenethaline. Phenethaline is an acid-base indicator. It changes from pink to colorless in a range of about 10 to 9. We've already calibrated the pH electrode, so we're ready to collect data. We're going to come down to collect data. We're going to do trigger prompt. We're going to wait 30 seconds for the electronics to warm up. Our first data point is going to be 0 milliliters of HCl added. This will give us the initial pH of the solution. When the CBL reading is stable, we're going to press trigger on the CBL and enter the volume from the burette in the calculator. 0.00 milliliters. We want to collect more data, so select more data. We're going to add one milliliter of the HCl solution. We're going to try and get as close to one milliliter as possible. If you don't end up with exactly one milliliter, simply read the volume and enter that value to the nearest hundredth of a milliliter. When this CBL reading is stable, press trigger on the CBL and enter the volume of the burette in the calculator. 1.00 milliliters. We want to collect more data, so select more data, press enter. You're going to add the HCl solution in one milliliter increments. Remember that you also want to include the volume that corresponds to the half equivalence point, the first equivalence point, the second half equivalence point, and the second equivalence point. You also want to record the volume when the indicator changes. The first indicator will change will be from pink to colorless. When the phenothaline has turned colorless, you now want to add three to four drops of bromcresol green. Bromcresol green turns from blue to yellow at a pH of about three to four. You want to continue to add the HCl solution in one milliliter increments, collecting data each time. Record the volume when the indicator changes from blue to yellow. Notice that carbon dioxide gas is being produced and released from the solution. When you've reached 50 milliliters and the CBL reading is stable, press trigger on the CBL and enter the value on the calculator, 50.00 milliliters. We're through collecting data, so go down, select stop. This is the graph of the titration of the sodium carbonate with hydrochloric acid.