Report

Purpose of Practicum The objective of this lab is to compare the appearance of changes in the pH of strong acids and weak acids titrated with NaOH. LITERATURE REVIEW Buffering solution or buffer solution is a solution which can maintain a certain pH to the effort to change the pH such as acid addition, base, or dilution. In other words, the pH of the buffer solution will not change even if the solution is added slightly stronger acid, strong base or if the solution is diluted. The buffer solution contains buffered solutes. The buffer has an acid-base component overcoming the decrease in pH. These acids and bases are conjugate pairs (Mangihut, 2009). The buffer or buffer buffer or buffer solution is a solution that can maintain a certain pH value. The most prominent feature of this buffer solution is that the pH of the buffer solution changes only slightly in the addition of a slightly strong acid. Furthermore, the buffer solution is a solution formed by the reaction of a weak acid with its conjugate base or by a weak base with its conjugate acid. This reaction is referred to as Conjugate acid-base reaction. Besides it has different properties with its forming components (Zulfiky, 2003). The nature of the buffer solution is that the pH of the solution does not change if it is diluted and does not change anyway if added to it slightly acid or base. Essentially a buffer solution composed of a weak acid and a conjugate base is an ionic equilibrium system in water, involving equilibrium of water and a weak acid equilibrium. In addition, there is a conjugate base ion derived from the salt or the reaction product between said weak acid with a strong base. The buffer can be defined as a weak acid / base mixture with its salt. The buffer function is to maintain the pH of the solution when relatively weakly added acid / basic base is added. The buffer capacity is a quantitative parameter that indicates strength (resistance) to maintain pH. (Chang R, 2006). In various activities involving reactions in solution, it is often necessary to have a fixed-price pH. Changes in pH suuatu system often have unwanted effects. However, buffer solutions can maintain the pH of the system against disturbances that may alter the pH. The natural buffer is present in the body of a living being and in nature (Mulyasa, 2009). The need for buffers is sometimes difficult because almost every analysis requires a relatively stable pH condition. Because of the large variety and types of buffers, the selection of buffers to be used becomes its own masalha. In choosing a buffer, which must be considered is the optimum pH and biological properties. Many types of buffers have an impact on biological systems, enzyme activity, substrate and covators (Riyadi, 2008). Tools and Materials Practicum A. Practicum Tools The tools used in this lab are cup glass, stirrer, measuring pipette, dropper dropper, pH stick and titration tool. B. Practicum Materials The ingredients used in this lab are HCL 0.1 M, aquades, 0.01 N NaOH, H3PO4 0.05 N, NaOH 0.05 N. Work procedures A. Titration of HCl OBSERVATION RESULT Observation result Table 6.1 Changes in pH of 0.1 mL HC solution with 0.01 M NaOH addition PH HCl solution Volume of NaOH 0.01 N added (ml) Titration Curve Relationship Between Changes in pH and volume of NaOH Table 6.2 Changes in pH of H3PO4 M solution with addition of NaOH with addition of 0.05 N NaOH PH of H3PO4 solution Volume of NaOH 0.05 N added (ml) Titration Curve Relationship Between Changes in pH and volume of NaOH DISCUSSION Buffer solution is a solution that serves to withstand extreme pH changes in the event of an increase in the number of H + and OH ions in solution. The buffer is composed of a weak acid with a conjugate base or a weak base with conjugate acid. The reaction between these two constituent components is called the acid-base reaction of the conjugate. Acidic acid solution will maintain the pH in the acidic region (pH <7) while the alkaline buffer solution will maintain the pH at base region (pH> 7) (Anonymous, 2013). This practice has two tests conducted namely HCl titration test and H3PO4 titration test. Where this lab is done to compare pH changes in strong acid and weak acid by titration using NaOH which concentration is 0,01 N (ml) and 0,05 N (ml). The HCl titration test was performed by titrating NaOH having a concentration of 0.01 N. In the titration test of HCL, which before adding 0.01 N NaOH (ml) the pH of this solution was 2, after added the first 5 ml of NaOH obtained Ph 2, The second 5 ml was pH = 2, at the 5 ml of the third the pH was changed to 3. Then the 5 ml of the fourth increased to pH = 4, in the 5 ml of the five pH to 6 and in the addition of the last 5 ml the pH rose to 9. Based on the observations obtained An increased curve. It can be concluded that this buffer solution is strongly acidic because it can maintain pH so that more than 7 where in the solution from 0 to 30 ml the pH of the solution increases. In the second test, the test of H3PO4 solution using NaOH with concentration of 0.05 N (ml). Before adding NaOH to the first 5 ml of pH of solution 2, after adding 5 ml second and third pH of the solution remained 2, in addition of 5 ml fourth and fifth pH to 3, and at 5 ml next pH increased to 5 and at last 5 ml pH- It becomes 6. Based on the data of this buffer solution is a weak acid because its pH is less than 7. The addition of acid (H +) will shift the left equilibrium. Where the added H + ion reacts with CH3COO ions to form CH3COOH molecules. If an alkaline solution is added then the OH-ion of the base will react with the H + ion then it can form water. This will cause the equilibrium to shift right so that the concentration of H + ions can be maintained. Thus, the addition of a base causes a reduction in the acid component. The addition of NaOH will destroy the OH ions so that the pH becomes elevated. Most biochemical reactions in the body of a living being can only take place at a certain pH. Therefore, body fluids should be buffering solutions to keep pH constant when metabolism takes place. Because the buffer system will maintain the pH of the body to remain normal. CONCLUSION Based on the results of observation and discussion it can be taken some conclusions as follows: 1. Buffer solution is a solution that serves to withstand extreme pH changes in the event of an increase in the number of H + and OH ions in the solution. 2. Two tests were performed ie HCl titration test and H3PO4 titration test. 3. This HCl buffer solution is strongly acidic as it can maintain a pH of more than 7. 4. This H3SO4 buffer solution is weakly acidic because its pH is less than 5. The body fluid should be a buffer solution so that the pH is always constant when the metabolism takes place.