Determination of Ka of a Weak Acid by Titration Lab The purpose of the lab is to determine the dissociation constant of a weak acid through an acid-base titration. An unknown acid was added to DI water to form a solution. Phenolphthalein was added to the acid solution. The acid solution was then titrated with sodium hydroxide until it reached the endpoint. The same amount of acid solution was added to the titrated solution in order for the solution to reach its midpoint. The experiment was repeated. Theories and concepts explored in the experiment include dilution, equilibrium reactions, acid-base indicators, titration, weak acid-strong base reaction, pH, conjugate bases, equivalence point, endpoint, midpoint, dissociation, equilibrium reactions, …show more content…
At the start of the experiment, an unknown acid, the solute, was dissolved in DI water, the solvent, diluting the concentration of the acid. Phenolphthalein, an acid-base indicator--or a weak acid that changes color when the equivalence point is reached--was added to the solution. The solution was then titrated, a process by which a solution with a known concentration, NaOH, is added to an unknown solution, the acid, in order to determine its concentration. The reaction consisted of an unknown weak acid and NaOH, a strong base, making the reaction a weak acid-strong base reaction. Because NaOH is a strong base, the pH of the reaction--or the measure of the acidity of the solution by taking the negative log base ten of the hydronium concentration--would increase when titrating the unknown acid. As the unknown acid was titrated, one of the products formed in the reaction was the ion of the unknown acid, or the conjugate base which, according to the Brønsted-Lowry theory, was formed as a result of the acceptance of a hydrogen ion from NaOH. When the moles of the unknown acid and the …show more content…
One example of an error was fluctuating temperatures from air vents during the experiment. Because the Ka value is dependent solely on temperature, a slight increase in temperature for instance, can shift the reaction to the right, increasing the solubility of the reaction. This as a result, would have increased the concentrations of the products and the Ka value, explaining the 60.5% deviation in trial four. Another possible source of error is the loss of acid solution as it was transferred from the Erlenmeyer flask to the beaker. Although a small volume of the solution would have been lost, it is significant as a smaller volume would result in a lower volume of NaOH needed to titrate the acid, lowering the pH. A lowered pH would result in a higher Ka value, explaining the pH deviation of 33.3% from the actual pKa value in trial four and giving a reason as to why the Ka value in trial four is slightly higher than the other Ka
5. Question 5: a) As mentioned in the manual, we have the ratio (K/H+ ), if H+ was lower than K then the equivalent point will be achieved and it will change color. And if H+ was more than K then the solution we are titrating will be the same, the equivalent point won’t be achieved, and it will be acidic solution. And to find the value of H+ is by having the value of pH, therefore the pH has changed from 7 to 9, which is by shifting from 10-7 to 10 -8 by adding the 0.01 of the base, and it will shift again from 10 -8 to 10 -9 by adding another 0.01 of the base to the solution , the different that’s added between the two shifting are close to each other which indicates that the
In the first part of the experiment, Part A, the standard solutions were prepared. As a whole, the experiment was conducted by four people, however, for Part A, the group was split in two to prepare the two different solutions. Calibrations curves were created for the standard solutions of both Red 40 and Blue 1. Each solution was treated with a serial 2-fold dilution to gain different concentrations of each solution.
Can Alka-Seltzer Act as a Buffer Against Acid Rain? Background: Acid rain is a product of rainfall being tainted by atmospheric pollution. This also means that it has high levels of hydrogen ions. When acid rain falls it has negative effects on natural environments such as aquatic life, plants, and infrastructure.
After obtaining an homogeneous mixture, the flask was placed in an ice bath during five minutes next to a graduated cylinder containing 5.0 mL of concentrated sulfuric acid. The temperature of the ice bath was recorded to be 1.1 °C. Likewise, a second graduated cylinder containing 1.8 mL of nitric acid and 2.5 mL of sulfuric acid was immersed in the cold ice bath to keep the three different solutions at the same temperature. Thereafter, the cold 5.0 mL of H2SO4 were added to the erlenmeyer flask containing the acetanilide solution, which remained in the cold water for approximately another 4 minutes.
3. Upon adding 20 drops of NaOH, a white precipitate was formed signifying acidic impurity. In the second NaOH mixture, about 20 drops were administered and no precipitate formed indicating that the ample is more pure than before. Data: Weight of flask = 75.10 grams Weight of the flask with solids =
Research Question: To investigate and compare how different temperature (5℃, 15℃, 25℃, 35℃, 45℃) can affect the concentration of carbon dioxide in soda water through titration with sodium hydroxide solution. Introduction: Carbon dioxide plays an important role in soft drinks. Soda water is manufactured by pumping carbon dioxide into water under high pressure. Carbon dioxide dissolves in water to form carbonic acid, which is the fizz we find in soft drinks. CO2 + H2O ⇌
Stoichiometry is a method used in chemistry that involves using relationships between reactants and products in a chemical reaction, to determine a desired quantitative data. The purpose of the lab was to devise a method to determine the percent composition of NaHCO3 in an unknown mixture of compounds NaHCO3 and Na2CO. Heating the mixture of these two compounds will cause a decomposition reaction. Solid NaHCO3 chemically decomposes into gaseous carbon dioxide and water, via the following reaction: 2NaHCO3(s) Na2CO3(s) + H2O(g) + CO2(g). The decomposition reaction was performed in a crucible and heated with a Bunsen burner.
Introduction: In this task I will be researching the effect that acid rain has on the rate of plant growth. Acid rain is any type of precipitation with a high pH, with high levels of nitric acids. The reason why I had chosen this topic was because acid rain seems to have a great effect on the effect of plant growth, and plants play a very important role in our ecosystem. Acid rain is a major problem in our environment when we are not able to neutralize the acidity.
The equation of the reaction between sodium hydroxide and ethanoic acid is as follows: CH3COOH + NaOH → CH3COONa + H2O We can measure the end point of titration process and we can also measure the amount of reactants. The concentration of ethanoic acid in the vinegar can be determined through stoichiometric calculations, Using the values obtained from the titration, and also the chemical equation as a reference. Phenolphthalein indicator is used in this acid-base titration Equipment and materials:
Its pH is greater than 7 and turns red litmus paper into blue. Acid- base neutralization is done by adding an acid to a base or a base to an acid until the substance has equal hydrogen and hydroxide ions. This is used to determine unknown concentration of a
Practical I: Acid-base equilibrium & pH of solutions Aims/Objectives: 1. To determine the pH range where the indicator changes colour. 2. To identify the suitable indicators for different titrations. 3.
Introduction Buffer is a solution that resists a change in pH when bases or acid are added. Solutions that are acidic contain high concentrations of hydrogen ions (H+) and have pH values less than seven. Buffer usually consist of a weak acid, and its conjugate base or a weak base and its conjugate acid. The function of buffer is to resist the changes in hydrogen ion concentration as a result of internal and environmental factor. This buffer experiment is important so that we relies the important of buffer in our life.
Introduction The goal of the experiment is to examine how the rate of reaction between Hydrochloric acid and Sodium thiosulphate is affected by altering the concentrations. The concentration of Sodium thiosulfate will be altered by adding deionised water and decreasing the amount of Sodium thiosulphate. Once the Sodium thiosulphate has been tested several times. The effect of concentration on the rate of reaction can be examined in this experiment.
Introduction Strong acids and strong acids both dissociate completely in water forming ions. However, strong acids donate a proton to form H3O+ along with a conjugate base and strong bases accept a proton to form OH- along with a conjugate acid. The chemical behavior of acids and bases are opposite. When they are together, their ions cancel out and form a neutral solution. In this experiment, HCl and NaOH will react to form NaOH and H2O with these two steps: The overall reaction is: Both Na+ and Cl- ions combine to form NaCl.
That caused a new initial reading of NaOH on the burette (see Table1 & 2). The drops were caused because the burette was not tightened enough at the bottom to avoid it from being hard to release the basic solution for titrating the acid. The volume of the acid used for each titration was 25ml. The volume of the solution was then calculated by subtracting the initial volume from the final volume. We then calculated the average volume at each temperature.