Matt Marthaler Quantitative Analysis: Real World Lab Determination of Carbonate and Bicarbonate in Soda by Titration Purpose: In this experiment, we will determine the concentration of carbonate and bicarbonate species in different sodas using the technique of titration. A primary standard used in this experiment is NaOH for the direct titration of the diprotic acid. Color indicators which utilize changes in pH will be used to determine the presence of the different species of the acid. Procedure: 1) Approximately 2 g of NaOH(s) pellets were placed in a 500mL volumetric flask and diluted to the mark with distilled water to make an approximate 0.1M solution. 2) Approximately 0.51g of KHP was weighed for three different samples for standardization of the base. 3) The KHP was dissolved in 25 mL of water, phenolphthalein was added and the solution was titrated with NaOH. 4) The mL required to reach the endpoint was used to determine the concentration of the base; the individual calculations were averaged to determine molarity. 5) 25 mL of each cold, fresh soda was measured in a graduated cylinder. Four sodas were used: Sprite, Sprite Zero, Sierra Mist Natural, and Diet Sierra Mist Natural. 6) The sample was then placed in a beaker with a magnetic stir bar. 7) Methyl orange indicator was added to the solution. 8) The solution was titrated with NaOH over a stir plate until an approximate endpoint was reached. 9) 25 new mL of each cold, fresh soda was measured in a graduated cylinder. Four sodas were used: Sprite, Sprite Zero, Sierra Mist Natural, and Diet Sierra Mist Natural. These samples were separate from the previous samples. 10) The sample was then placed in a beaker with a magnetic stir bar. 11) Phenolphthalein indicator was added to the solution 12) The solution was titrated with NaOH over a stir plate until an approximate endpoint was reached. 13) The relative percent carbonate and bicarbonate within Sprite, Sprite Zero, Sierra Mist Natural, and Diet Sierra Mist Natural was then calculated along with the standard deviation from these titrations. Data: Standardization of NaOH Trial 1 2 3 Average Standard Deviation Mass KHP (g) 0.5084 0.5090 Volume NaOH 1 (mL) 26.64 29.90 Molarity NaOH (M) 0.09345 0.08420 Mass KHP (g) 0.5092 0.5080 0.5061 Volume NaOH 2 (mL) 26.59 26.61 26.50 0.0888 Molarity NaOH (M) 0.09377 0.09348 0.09352 0.09359 0.006547 0.00015716 Titration of Bicarbonate Using Methyl Orange Trial 1 2 3 Average Standard Deviation (%) mL NaOH in Sprite 0.67 0.70 0.63 [HCO3-] 0.002380 0.002238 0.002238 0.002285 mL NaOH in Sprite Zero 1.00 0.81 1.31 0.000082 [HCO3-] 0.003552 0.002948 0.004653 0.003717 mL NaOH in Sierra Mist Natural 1.60 1.50 1.42 0.000864 [HCO3-] 0.005990 0.005615 0.005316 0.005640 mL NaOH in Diet Sierra Mist 1.49 1.58 1.27 0.000378 [HCO3-] 0.005292 0.005612 0.004511 0.005138 0.000566 Titration of Carbonate Using Phenolphthalein Trial 1 2 3 Average Standard Deviation (%) mL NaOH in Sprite 17.41 17.99 16.11 [CO32-] 0.1237 0.1278 0.1144 0.1197 0.0074 mL NaOH in Sprite Zero 17.91 17.01 18.51 [CO32-] 0.1272 0.1208 0.1314 0.1227 0.0071 mL NaOH in Sierra Mist Natural 20.69 18.66 18.11 [CO32-] 0.1549 0.1397 0.1356 0.1378 0.0123 mL NaOH in Diet Sierra Mist 20.20 20.39 19.86 [CO32-] 0.1435 0.1449 0.1411 0.1432 0.0066 Percent Carbonate and Bicarbonate in Soda in a 20 oz Soda Bottle Percent Bicarbonate (%) Percent Carbonate (%) Sprite Sprite Zero Sierra Mist Natural Diet Sierra Mist 0.01394 0.02668 0.03136 0.034408 0.73180 0.75880 0.85920 0.860339 Calculations: Amount of NaOH Pellets 0.1 moles NaOH x 0.5 L x39.997 g NaOH = 1.999 g NaOH pellets 1 L NaOH x 1 mole NaOH Mass KHP 25 mL x 1 L x 0.1 mole NaOH x 1 mole KHP x 204.221 g KHP = 0.5106 g KHP 1000 mL x 1 L x 1 mole NaOH x 1 mole KHP Molarity NaOH 0.5106 g KHP x 1 mole KHP x 1 mole NaOH x 1 x 1000 mL = 0.09345 M 204.221 g KHP x 1 mole KHP x 26.64 mL x 1 L Bicarbonate (Sprite) 0.0888 πππππ ππππ» π₯ 0.67 ππΏ π₯ 1 πΏ π₯ 1 ππππ π»πΆπ3 − π₯ 1000 ππΏ = 0.002380 πππππ π»πΆπ3 −/πΏ 1000 ππΏ π₯ 1 ππππ ππππ» π₯ 25 ππΏ π₯ 1 πΏ Carbonate (Sprite) 0.0888 πππππ ππππ» π₯ 17.41 ππΏ π 2 πππππ πΆπ3,2 − 0.1237 πππππ πΆπ3,2 −/πΏ 1 πΏ π₯ 1 ππππ ππππ» π₯ 25 ππΏ Percent Bicarbonate (Sprite) ππ£πππππ πππππ π₯ 61 π ππππππππππ‘π π₯ 591 ππΏ = 0.0823854 π ππππππππππ‘π 1 ππππ π₯ 25 ππΏ (0.0823854 g bicarbonate/591 g Sprite) x 100 = 0.01394% Percent Carbonate (Sprite) ππ£πππππ πππππ π₯ 60 π ππππππππ‘π π₯ 591 ππΏ = 4.244562 π ππππππππππ‘π 1 ππππ π₯ 25 ππΏ (4.244562 g bicarbonate/591 g Sprite) x 100 = 0.7318% Conclusion: Our experiment cannot be considered entirely accurate, but it was not a failure. Some of the inaccuracies come from: ο½ Re-standardization of more NaOH due to a short supply of the solution in the middle of the experiment ο½ Inconsistencies due to the gradual color change of methyl orange. We did not know when to stop the titration since the color of orange is difficult to read consistently. ο½ Due to the carbonation in soda, a graduated cylinder was used to measure the volume of soda since the bubbles made it impossible to use a pipet. ο½ The density of water was used to calculate the percent carbonate and bicarbonate since there are not published values for the density of the different sodas ο½ When measuring the acidity of these beverages, other acids present in the soda such as citric acid can distort the perception of carbonic acid and change results. Regardless of the possible reasons for error, the standard deviations of this experiment were reasonable, so precision was achieved within the calculations. The amount of carbonate and bicarbonate were determined, therefore, the experiment was successful and error can be acknowledged. We have found out that Sierra Mist has more Carbonate and Bicarbonate than Sprite and also that diet sodas have more carbonation than regular sodas.