Acid-Base Lab

The purpose of doing this lab was to apply the knowledge of chemical reactions to identify an unknown substance. Research was done prior to doing the experiment to provide a basic understanding of the chemical reactions occurring. There are two elementary aspects a chemical solution. First, there’s the reactant. The reactant is the substance added that reacts with another chemical, after the chemical reaction has run its course, what is left is called the product. There are about seven ways to tell if a chemical reaction has taken place; a few of which include color change, precipitate, the formation of gas, and temperature change. In this particular experiment, the question that was being investigated was: What is the unidentified chemical substance? The hypotheses made was: The unnamed chemical is Calcium Chloride considering each are clear liquids.

In this experiment, a mixture of unknown #3 was used. That mixture had acid, base, and neutral. We added solvent to the unknown. It is important to know the density of the solvent in order to determine which is the aqueous layer and which is the organic layer. If the solvent that has more density than water, so the organic layer will be the lower layer, while if the solvent has lower density than water, the organic layer will be the upper layer. This will make an error if the determination of the layers was wrong after added the strong acid or the strong base. We added 5% HCl to the mixture in order to separate the base in the aqueous layer and form its salt. Same thing, we add 5% NaOH to the mixture in order to separate the acid and form its salt. In order to recover the base, we add 10% NaOH to the HCl extraction. The result will be salt with a base. Same thing for the acid, in order to recovered it, we added 10% HCl. The reaction will give us salt with an acid. For the neutral, we added sodium sulfate as a drying reagent in order to dry water and separate the neutral part as pure.

The mixture might have contained more or less than 5 drops of bromophenol blue, which might have resulted in the indication of the lab.

The objective of this lab was to use qualitative and quantitative measurements and observations to properly identify, and then confirm the identity of an unknown compound. After identification, the compound would have to be synthesized, in our case, through an acid-base reaction, followed by confirming its identity with the original unknown compound.

In the first part of the experiment (identifying the chemical makeup of the unknown compound

The range determined in the experiment is approximately 2 degrees above the actual melting point range, indicating some impurities in the final compound. According to the IR spectrum, the product obtained is quite pure. The peaks in the table above indicate the presence of a carbonyl, specifically the C=O bond of a cyclic ketone and also the sp2-hybridized =C–H bond of an alkene. There is no broad peak ranging from 3200 cm-1-3600 cm-1, which would indicate the presence of the -OH group of an alcohol. Thus, there is likely no presence of starting material in the final product. The percent yield above 100% indicates that some liquid (hexanes) used to recrystallize the product was likely still in the flask when the product was weighed.

Objective: The objective of this experiment is to use acid-base extraction techniques to separate a mixture of organic compounds based on acidity and/or basicity. After the three compounds are separated we will recover them into their salt forms and then purify them by recrystallization and identify them by their melting points.

Identifying the three components of the unknown mixture, a 1.5 g sample was obtained and dissolved in 30 mL of diethyl ether. This solution was then poured into a separatory funnel with a funnel with the stopcock closed, and inverted twice so that there would be a formation of different layers in the mixture. In order to extract the base from the mixture, approximately 14 mL of 10% hydrochloric acid was added into the funnel and mixed. To mix the hydrochloric acid thoroughly the funnel was gently shaken with the pressure released by removing the stopper intermittently. The solution then separated into an aqueous layer at the bottom, and an organic layer at the top (containing the acid).1 The aqueous layer (containing the base) was released into an

The decanted liquid had to be placed back into the freezer in order to refreeze the crystals to allow them to be decanted off. This could have caused a portion of the product to have been lost, thus affecting the percent yield and purity of the final product. Furthermore, there was an oiled substance thought to be a contaminant in the product after the addition of hot methanol and hot water to the Erlenmeyer flask. This contaminant was left in the Erlenmeyer flask to see whether or not it had an effect on the final product, but once the activated charcoal was added into the Erlenmeyer flask, the contaminant seemed to have latched onto the charcoal. Since it latched onto the charcoal and the charcoal was filtered out by way of gravity filtration, the contaminant is thought to have been filtered out as well. While the contaminant seemed to have been filtered out by the gravity filtration, there could be a small portion of the contaminant that remained in the filtered-out product, thus affecting the percent yield and purity of the final product as

Experiment 4A: Determination of a Partition Coefficient for Benzoic Acid in Methylene Chloride and Water, and Experiment 4B: Solvent Extraction I: Acid-Base Extraction Using the System Benzoic Acid, Methylene Chloride, and Sodium Bicarbonate Solution

In this particular experiment, unknown compound three was identified and was found to consist of the carboxylic acid 2-chlorobenzoic acid, as well as the phenol 2-naphthol. This was determined using the melting points of the substances. The first substance had a melting point of 134.0°C, which is very close to the literature value of 138-140°C1 for 2-chlorobenzoic acid. The other substance had a melting point of 126.5°C, which is also very close to the literature melting point of 120-122°C1 for 2-naphthol. Out of the 1.001g of the original unknown sample, 0.456g of carboxylic acid and 0.448g of the phenol were recovered.

The objective of the lab was to purify compounds that can be turned into gas at a reasonable temperature without using decomposition. Gas chromatography was also used to identify the proportions of the volatile compound in the different samples. The mixture of hexane and octane was assigned to me and my partner. The apparatus for simple distillation was assemble using a thermocouple, air condenser, distillation head, metal keck clamps, and a conical reaction vial. The joints of the glassware were greased before assembly. Four boiling chips were placed in the conical ration vial before it was assembled. After being assigned a mixture, 3.5 mL of the mixture was put into a reaction vial. The apparatus

Just like any other experiment, this experiment was sure to have flaws. Luckily, we didn’t have any major flaws, but we did have some minor ones that could have impacted our experiment. As you can see, our results turned out to be exactly like our hypotheses, and we strongly believed in our hypotheses. I can only think of two things that I know we did wrong, and these are we spilt a liquid while closing the tubes once, and we also forgot to start a timer for the 10-minute room temperature. This was not too bad though, considering it was going to sit in room temperature for the rest of the

The beaker was slowly heated on a hot plate with low stirring until most of the stilbene was dissolved. 0.4 g of pyridinium tribromide was measured and added to the beaker after 5 minutes of heating. Small amounts of ethanol were used to clean the sides of the beaker. The beaker was heated for an additional 10 minutes on low temperature. An ice bath was prepared. The beaker was removed from the hot plate and left to cool to room temperature. Once at room temperature, the beaker was placed in the ice bath for 15 minutes. The solid product was collected through vacuum filtration and the product was weighed and a melting point was taken. Waste was disposed of in the correct waste bins and lab bench was cleaned

An acid-base titration is the determination of the concentration of an acid or base by exactly neutralizing the acid/base with an acid or base of known concentration. This allows for quantitative analysis of the concentration of an unknown acid