Titration Lab Write Up free essay sample

Abstract The purpose of this experiment is to determine the concentration of acetic acid in vinegar by using 0.1 M HCl and NaOH solution. By performing three titrations to determine the concentration of the base, the concentration of the acid was determined to be 0.600 M. It was possible to determine its concentration by standardizing the sodium hydroxide solution used for the first three titrations and by using phenolphthalein to indicate its equivalence point. In conclusion, although there were sources of error, the hypothesis was proven correct by the efficiency of the procedures and the accuracy of the results obtained. Introduction In chemistry, titration is a common laboratory technique that is used to determine the concentration of a substance in a solution. It is performed by neutralizing the solution with the same volume of either an acid or base with a known concentration. (â€Å"Titration.† American Heritage Science Dictionary. 2010) Once the neutralization is complete, the concentration is determined by using the formula MAVA = MBVB. We will write a custom essay sample on Titration Lab Write Up or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page The basis of this process is that there are three known values and one unknown value. However, how is the concentration of a substance in a solution determined when there is another unknown value? An experiment was created with the purpose of answering this question by performing three titrations to obtain the value of one unknown concentration and using this value to determine the concentration of the acid used. Hypothesis If three titrations are performed using 0.1 M HCl and NaOH solution to obtain the molarity of the base, then this information can be used because by titrating the vinegar with the now known concentrated base, the concentration of the acetic acid can be determined. Materials and Methods All materials were gathered including a buret, graduated cylinder, stopcock, phenolphthalein, an Erlenmeyer flask, sodium hydroxide solution and hydrochloric solution. The buret and graduated cylinder were rinsed with water and any excess water draining out of the buret was discarded. To start the titration process the stopcock was closed and the buret was filled with sodium hydroxide until it reached the 0 mL mark. To measure approximately 10 mL of HCl solution, a graduated cylinder was used and this acid was placed into an Erlenmeyer flask. Its exact volume was recorded as well the initial reading of the sodium hydroxide in the buret. The acid was added to the flask by slowly opening the stopcock. During this step, the solution was constantly swirled to mix the acid with the base and caution was taken care of the solution’s color by immediately closing the stopcock once it reached a permanent pink color. Once the solution reached its endpoint, the readi ng was recorded and this procedure was repeated for the next three titrations. One exception was that during the fourth titration, 5.1 mL of the vinegar or acidic solution was used instead of 10 mL After all four titrations were completed, all materials were rinsed thoroughly. Results Trial # VA VB 1 10.00 mL At start: 0 mL At finish: 4.6 mL VB: 4.6 mL 2 10.00 mL At start: 4.6 mL At finish: 8.8 mL VB: 4.2 mL 3 10.00 mL At start: 8.8 mL At finish: 13.7 mL VB: 4.9 mL Vinegar 5.100 mL At start: 13.7 mL At finish: 27.0 mL VB: 13.3 mL The results show that for the first three trials, 10.00 mL of the same acid was titrated with sodium hydroxide. 4.6 mL of the base was used to titrate the acid after the first trial, 4.2 mL after the second trial and 4.9 mL after the third trial. For the final trial, 5.100 mL of vinegar was used as the acidic solution and 13.3 mL of the base titrated it. Calculations Trial #1 = 0.217 M NaOH MaVa = MbVb (0.1)(10.00) = (x)(4.6) → 0.217 Trial #2 = 0.238 M NaOH MaVa = MbVb → (0.1)(10.00) = (x)(4.2) → 0.238 Trail #3 = 0.204 M NaOH MaVa = MbVb → (0.1)(10.00) = (x)(4.9) → 0.204 0.217 + 0.238 + 0.204 3 = 0.220 Average Mb = 0.220 M NaOH MaVa = MbVb → (x)(5.1) = (0.220)(13.3) → 5.1x = 2.926 → x=0.574 Ma = 0.600 M Determining the Legality of the Vinegar Used g 1.1 L = 1.0 g → 1.5 L = 1500 g Discussion During the experiment, certain materials and methods were used to determine the concentration of the acetic acid in vinegar such as titration, phenolphthalein to indicate the equivalence point and standardizing the sodium hydroxide solution before performing the first three titrations. Titration was used to determine the concentration of the acidic solution by neutralizing it with a basic solution with a known concentration. Then, the volume of the base, concentration of the base and the volume of the acid were plugged into the formula, MAVA = MBVB. Phenolphthalein was used by indicating when the solution reached its equivalence point by turning its color to a permanent pink. Any other indicator such as methyl orange wouldn’t have worked out as well because when it would change the solution’s color to indicate the equivalence point, it wouldn’t be clear whether the solution was acidic or basic since its color would be the same as its initial color. The equivalence point is the point at which the acid and base are equal. Every neutralization reaction reaches this point since these types of reactions require equal amounts of both the acid and base in order to neutralize each other. Finally, it was important to standardize the sodium hydroxide solution in order to titrate the solution of vinegar because it helped avoid any other additional dependent variables and served as a constant during the experiment. If different amounts of the NaOH solution were used during the titrations, then inaccurate results would have been obtained since the concentration of the acid would have been calculated incorrectly. The obtained concentration of the acetic acid in vinegar was 0.600 M. According to legal terms, for vinegar to be legal, it must contain at least 4% acetic acid. The amount of acetic acid in legal vinegar is equal to at least 1 mole. However by using the formula for determining the molarity of a substance and a simple proportion, it was found that the vinegar used during the experiment was not legal. Conclusion The significance of the results is that they proved our hypothesis correct by showing that the procedures used did achieve the purpose of the experiment by successfully helping us determine the concentration of acetic acid in vinegar. Although the obtained concentration was off by 25% compared to the expected concentration, the results were accurate in that they showed the molarity of the acid was fairly higher than the concentration of the base used because a lesser volume of the acid was used than the base. This percent error may have occurred due to a source of error found in the stopcock. A leakage of the NaOH solution through the stopcock may have resulted in inaccurate recordings of the volumes of the base used in each trial and therefore a lower concentration of the acetic acid was calculated. An improvement that can be made to the experiment is by opening the stopcock just a little so that only drops of the NaOH solution would fall into the flask. Even though it would take longer to complete the experiment this way, this would help achieve more accurate results.