An investigation was conducted to determine an unknown concentration of ethanoic acid in various types of vinegar. Vinegar is a liquid that consists of around 4-8% ethanoic acid (CH3OOH), water and other trace chemicals (Wikipedia, 2018). The vinegars used in this experiment were wine, white wine and apple cider and they have 6%, 5% and 4% ethanoic acid concentrations respectively (University of Sydney, n.d). Vinegar is produced by the fermentation of ethanol by acetic acid bacteria. An acid is considered strong if they completely ionise in water to produce hydrogen ions and have a low pH, an example of a strong acid is hydrochloric acid (HCl). Weak acids, however, do not fully ionise and instead form an equilibrium mixture. Ethanoic acid …show more content…
Sodium hydroxide (NaOH) is an example of a strong base and is what was used in this experiment. A weak base does not fully ionise and in aqueous solutions, reacts incompletely with water to yield hydroxide ions (lumenlearning, n.d).
The solution with the unknown concentration but known volume (vinegar) is called an analyte and a solution with a known concentration (sodium hydroxide) is called the titrant. In titration, the titrant is added to the analyte to achieve the equivalence point and determine the concentration of the analyte. In this experiment, the ethanoic acid was combined with sodium hydroxide to produce a neutralisation reaction. This can be seen in equation 2.
Equation 2: Neutralisation reaction between vinegar and sodium hydroxide
CH3COOH(aq) + NaOH(aq)==> CH3COONa(aq) +
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It occurs when enough base is added for a neutralisation reaction to occur. The equivalence point between a weak acid and a strong base is pH 8.72. It must be attained precisely to produce accurate results. This is done by slowly adding the titrant to the analyte. The end point of the experiment refers to the point at which the indicator changes colour because of an indicator. The indicator phenolphthalein has a pH range of 8.2 to 10.0 and is used to determine the endpoint as it shows when enough of the base has been added to fully react with the acid. It remains colourless in an acid and when neutral, however, when the solution becomes basic, it turns pink. When it turns a pale pink, the endpoint has been reached and the amount of base can be determined, and the concentration of acid can be found. However, if the solution is overly titrated, it will turn a bright pink. This means that the results are no longer precise nor accurate. When the endpoint has been reached, the amount of base used can be determined, and thus the concentration of the acid can be found using
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.
4. NaOH, sodium hydroxide is a strong base. It reacts with HCl and forms NaCl and H2O.
Observe and measure a weak acid neutralization and determine the unknown identity of an unknown acid by titration.
The purpose of the experiment was to determine how a buffer works and how to use an acid-base indicator. The way a buffer works was determined by observing the changes in pH of solutions of different concentrations weak acids and their conjugate bases to determine how a buffer affects the pH change. The solution of 10 mL of 0.20 M CH3COOH and 10 mL of 0.20 M CH3COONa had slighter changes in pH than the solution of 10 mL of 0.0020 M CH3COOH and 10 mL of 0.0020 M CH3COONa. Both of these solutions were buffers, shown because they had slighter changes in pH than the solutions with only the weak acid or conjugate base and water. The determination of how buffers work was also tested with observing that the solution of NaC4H3O4 and Na2C4H2O4 had smaller
The purpose of this lab was to experiment with triprotic acid to create different salts through neutralization. Specifically, using varying volumes of sodium hydroxide with a constant 1 mL of 6M Phosphoric acid. In doing so one can examine the reactions and use stoichiometry to identify the products formed from the relationship between the reagents.
weak bases). After ranking the pH of these solutions, you will then test your predictions in the laboratory.
By using acid-base titration, we determined the suitability of phenolphthalein and methyl red as acid base indicators. We found that the equivalence point of the titration of hydrochloric acid with sodium hydroxide was not within the ph range of phenolphthalein's color range. The titration of acetic acid with sodium hydroxide resulted in an equivalence point out of the range of methyl red. And the titration of ammonia with hydrochloric acid had an equivalence point that was also out of the range of phenolphthalein.. The methyl red indicator and the phenolphthalein indicator were unsuitable because their pH ranges for their color changes did not cover the equivalence points of the trials in which they were used. However, the
solution is acidic. When it is green to yellow, it indicates that a solution is basic. When it is purple to blue, it indicates a solution is neutral. Would you characterize vinegar and ammonia as acids or bases? Explain.
Experiment to investigate the amount of sodium hydroxide needed to neutralize the solution of vinegar
Second, the plunger of the titrator was depressed. Third, the titrator was inserted into the plug in the top of the Sodium Thiosulfate titrating solution. Fourth, the bottle was inverted and the plunger was slowly withdrawn until the large ring on the plunger is opposite the zero line on the scale. If a small bubble appeared in the the titrator barrel, it was expelled by partially filling the barrel and pumping the titration solution back into the reagent container. This was repeated until the bubble disappeared. Fifth, the bottle was turned upright, and the titrator was removed. Sixth, the tip of the titrator was inserted into the opening of the titration cap. Seven, the plunger was slowly depressed to dispense the titrating solution until the yellow-brown color changed to a very pale yellow. The tube was gently swirled during the titration to mix the contents. Eight, the titrator and cap was carefully removed, while the titrator plunger was not disturbed. Nine, eight drops of Starch Indicator Solution was added. The sample had turned blue. Ten, the titration tube was capped. The tip of the titrator was inserted into the opening of the titration tube cap. Eleven, the titration was continued until the blue color disappeared and the solution became colorless. Twelve, the test result was read directly from the scale where the large ring on
In this lab a acid-base indicator phenolphthalein was used to determine endpoint of a reaction HCl(aq) and KOH(aq). At the end point all of the HCl(aq) would have reacted with KOH(aq), and the pH becomes 7. The phenolphthalein would changed colours from colourless to pink indication when enough KOH(aq) was added. The purpose of numerous trials was to use the average volume of the 3 trials with similar measurements.
For this experiment, a pH meter was used so this part of the experiment began with the calibration of the pH meter with specified buffers. The buret was then filled with the standard HCl solution and a set-up for titration was prepared. 200g of the carbonate-bicarbonate solid sample was weighed and dissolved in 100 mL of distilled water. The sample solution was then transferred into a 250-ml volumetric flask and was diluted to the 250-mL mark. The flask was inverted several times for uniform mixing. A 50-mL aliquot of the sample solution was measured and placed unto a beaker. 3 drops of the phenolphthalein indicator was added to the solution in the beaker. The electrode of the pH meter was then immersed in the beaker and the solution containing the carbonate-bicarbonate mixture was titrated with the standard HCl solution to the phenolphthalein endpoint. Readings of the pH were taken at an interval of 0.5 mL addition of the titrant. After the first endpoint is obtained, 3 drops of the methyl orange was added to the same solution and was titrated with the standard acid until the formation of an orange-colored solution. Readings of the pH were also taken at 0.5 mL addition of the titrant.
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
By using the pH paper to measure the solutions A through E it would point out what substance is an acid and which one was basic. Also, by adding Bromothymol blue and Phenolphthalein afterwards to the solution it would indicate what color it would turn to when mixed into an acid and a base.
Weak bases do not furnish OH- ions by dissociation. They react with water to furnish the OH- ions. For example, When a weak base reacts with water the OH- comes from the water and the remaining H+ attaches itself to the weak base, giving a weak acid as one of the products. You may think of it as a two-step reaction similar to the hydrolysis of water by cations to give acid solutions.