Levels Of Acid-Buffer Titration

“The pH of a solution is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of the acidity or basicity (sic) of the solution. The letters pH stand for power of hydrogen and the numerical value defined as the negative base 10 logarithm of the molar concentration of hydrogen ions.” (PH, 2002). The pH scale is from 0 to 14. When the pH is higher, the hydrogen ions are fewer and the substance considered alkaline. This means when a pH unit increases by one, there is a tenfold change in the hydrogen ion. For example, if a substance has a 7 pH, it has 10 times as many as hydrogen ions available as 8 pH. A lake having a water pH between 6.5 and 8.5 is considered to be neutral. Researchers tested Peckham Park lake water monthly from August 2015 to April 2016 for water pH levels. A water quality PH test strip taken from a jar and dipped into the lake. After a few minutes, the strip will turn a color and this color determines the pH. The jar the strips came in has a chart of the colors on the back which compared to the color on the strip. The lake tested monthly using the PH test strips, which show the pH level, hardness, toxic, etc. using color-change

weak bases). After ranking the pH of these solutions, you will then test your predictions in the laboratory.

To start out this study the difference between acids and bases has to be identified. Acids have very low pHs and have a high concentration of hydronium ions, while bases have a high pH and have a high concentration of hydroxide ions. The difference between strong bases and acids, and weak bases and acids is the amount of dissociation. Strong bases and acids dissociate a large amount and let go of their ions in solution, while weak bases and acids may only let go of some of their ions. This is important because if the unknown solutions aren’t strong acids or bases then using their ions to calculate the pH of the solutions will give false results (Diffen 2012).

The purpose of this experiment was to determine the pKa, Ka, and molar mass of an unknown acid (#14). The pKa was found to be 3.88, the Ka was found to be 1.318 x 10 -4, and the molar mass was found to be 171.9 g/mol.

pH is also known as a measure of hydrogen ions in a solution. A hydrogen ion is the nucleus of a hydrogen atom being split from its electron. Studying the pH of different types of soil being placed in a control group such as tap water will represent the acidity or alkalinity of the matter. The pH scale begins at 0 and goes all the way up to 14, pH 7 being its neutral point, which isn’t acidic or basic. A neutral point on the acidic scale is in the middle, anything lower than the neutral point (7), is acidic, and anything higher than the neutral point is considered basic or “alkaline”.

The higher the hydrogen ions amount the lower the pH number, the lower the hydrogen ions amount the higher the pH number. Some examples of acidic, neutral and basic materials that are commonly known are: Lemons (acidic), Water (neutral), Bleach (basic).

Within an acid-base titration the titration curve resembles the strengths of the corresponding acids and bases. A strong acid will correspond with a weak conjugate base, and a weak conjugate acid will correspond with a strong base. This is based on the Bronsted-Lowry model. The weak acid will donate protons to the hydroxide ion. Weak acids will have a low Ka value, the Ka value is the tendency of the acid to dissociate:

The standardized concentration of NaOH was used to identify the unknown acids, this value is shown is experiment 16.1. This mean standardized concentration was 0.0784 M. By titrating a known amount and concentration of this standardized base to the unknown acid, a titration curve and its derivative could be plotted in order to find the molar mass and acid dissociation constant. The first unknown acid titrated, BGYW, was identified to be Maleic acid, C4H4O4.

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

The pH of a solution is the measure of the concentration of charged Hydrogen ions in that given solution. A solution with a pH lower than seven is considered to be acidic. A solution with a higher pH is a base. It is very important for organisms to maintain a stable pH. Biological molecules such as proteins function only at a certain pH level and any changes in pH can result in them not functioning properly. To maintain these constant pH levels, buffer solutions are used. A buffer solution can resist change to small additions of acids or base’s. A good buffer will have components that act like a base, and components that act like an acid.

For this experiment, titrations on a weak acid, acetic acid, and a buffer were performed. Acetic acid was titrated with NaOH in order to observe the half-equivalence point as well as the equivalence point. Then, the buffer and the buffered acetic acid solution prepared faced additional titration with NaOH and HCl to evaluate the differing buffering effects following the addition of a strong acid and strong base. Finally, the buffer’s buffering capacity was calculated. If the experiment were to be repeated, it would be interesting to observe the buffering effects following a titration between a weak base and a buffer instead with greater concentrations. The change in the concentration following the preparation of buffer with a weak base and its conjugate acid would pose for an interesting experiment to observe an increase in the buffering capacity.

The titration of a strong base (NaOH) against a weak acid (Histidine monohydrochoride ) enables us to know of properties of the weak acid (histidine). Such properties include the pKa of the acid and the pH range of the buffering capacity. One way to relate pH to pka would be through the Henderson – Hasselbalch equation as stated below.

Table1: The amount of volume (in cm3) and concentration (in M) of KI, KIO3, and H2SO4 which were used in the experiment of Vit C estimation by back titration.

Changes in the hydrogen potential (pH); defined as the “negative logarithm of the concerntration of hydrogen ions” (Destiny, 2012). Hydrogen potential is measured on a scale of from 0 to 14, with the value of zero being the most acidic (academia) and 14 being the most basic (alkalemia). The presence of the hydrogen ion that is responsible for changes on the acidity of the extracellular fluid is derived from body activities such as aerobic and anaerobic respiration, incomplete oxidation of fatty acids, oxidation of amino acids containing

pH is a measure of the hydrogen ion activity in the water and is determined by the relative number of the hydrogen ions for acidity and hydroxide ion for alkalinity, thus mathematically expressed as pH=-log [H+] where [H+] is the hydrogen ion activity . pH values are calculated in powers of 10.Thus, the hydrogen ion concentration of a solution