Titration Lab -20points
In the restaurant industry, a chef controls the quality of the ingredients coming into the kitchen. Just like in the restaurant industry, chemists can control the quality, or molarity, of a given substance through titration. Titration is a process in which you use a given volume of a substance, dubbed substance A, and using the same amount of another substance, dubbed substance B, to determine the molarity of substance A. In this process, indicators are used to tell when the endpoint of the titration is reached, cabbage juice of phenophathalein. So, if one were to know the volume of substance A and the molatrity and volume of substance B, one would be able to figure out the molarity of substance A.
MATERIALS AND METHODS
One 100 mL volumetric flask was obtained. 1.16 grams of sodium hydroxide was also obtained and placed into the volumetric flask. Then, water was added to the flask up to the engraved line on the neck of the flask. The first time the flask was over filled. On the second attempt, the flask was filled up to the engraved line and shook up, creating the base needed for the trials. Then two burettes, a 50 ml and a 100 ml beaker and a ring stand were obtained. After cleaning each out, we added 25 mls of water to each of the beakers and then added the indicator, cabbage juice for the HCl and Phenophtalein for the vinegar. The acid was added to the black burette and the base was added to the blue burette. The beakers were filled with water and indicator was added to both the beakers. Acid was then added to one of the beakers, labeled variable, and the other beaker was kept without acid and labeled control. The beaker with the acid in it was given a quantity of base to get it back to the same color indicator as the control beaker. This process was repeated two more times with varying quantities of acid and base. The base was then transferred into a volumetric flask for storage because class ended. When the lab was resumed, a clean burette was obtained and the base was transferred yet again into the burette. Then, a clean beaker and another clean burette was obtained. Spartan brand vinegar was added to the beaker and another beaker was obtained. Water was added to the second beaker as was five drops of the indicator, phenophtalien. Then, the Spartan brand vinegar went into the clean burette and the acid was added to the beaker with the indicator, then base was added until the titration reached the endpoint. This process was completed twice more with the Spartan brand vinegar using varying quantities of acid and base. Not all of the Spartan brand acid was used, and the rest of it was traded to another group for the Heinz brand vinegar. A 100 mL beaker was cleaned out and 25 mLs of water were added to it along with the indicator.
Varying amounts of acid and base were added to the beaker with the indicator over the course
of three trials. The same control beaker was kept throughout the vinegar titrations.
Table 1: Standardization of Base
Trial 1 Trial 2 Trial 3 Molarity of Acid 1.008 M HCl Final height acid 18.7 17 16 Initial height acid 24 18.7 17 amount of acid used 5.3 1.7 1
Final height base 43.5 42 41 initial height base 45 43.5 42 amount of base used 1.5 1.5 1 Molarity of Base 0.433324 0.408 0.39337 Average molarity of
BaseA 0.412 M NaOH
Table 2: Determining Molarity of Vinegar
Spartan Vinegar Heinz Vinegar
Trial 1 Trial 2 Trial 3 Trial 1 Trial 2 Trial 3
Molarity of Base 0.412 0.412
Final height base 40.0 38.0 36.5 34.5 33.5 32.0
initial height base 41.0 40.0 38.0 36.5 34.5 33.5
amount of base used -1.0 -2.0 -1.5 -2.0 -1.0 -1.5
Final height acid 35.0 33.0 31.5 29.5 28.5 27.0
Initial height acid 37.0 35.0 33.0 31.5 29.5 28.5
amount of acid used -2.0 -2.0 -1.5 -2.0 -1.0 -1.5
Molarity of Acid 0.206 0 0 0.412 0 0
Average Molarity 0.309 M HC2H3OH 0.309
The hypothesis, stated above, said that if one knew the amount of substance A put into a titration and also knew the Molarity and volume of Substance B added to the titration, you can find the Molarity of substance A. This hypothesis, in this lab, proved to be correct. Again, it is like quality control in a restaurant, the cook controls the quality of the ingredients in the food and a chemist controls the quality, or “molarity”, of an acid or base. In this lab, the Spartan proved to be the better buy as they both have the same molarity and the Heinz, being name brand and in a smaller package, was more expensive then the Spartan, which came in a bigger container and cost less. This proved that when you need to be careful when you buy name brand verse non name brand products, as one of them may not really be worth as much. In the conclusions you need to state the molarity of the base from the titration and compare it with the calculation based on the mass, and then put how your precision was. You also need to state the molarity of the Spartan and Heinz vinegar and state how your precision was with that. -10 points