The pH at Different Points of the Unknown Acids Concentration - Lab Report Example

? PH Titrations Background Titration or titrimetry involves a method of laboratory that is used to analyze chemicals quantitavely and to determine the concentration of the unknown solution. The process is depended on the volume of a solution, a process that is referred to as volumentric analysis. A standard solution is defined as a reagent. In most cases, a concentration that is known reacts with the titrant volume to establish the concentration. Titration involves a group of experiments in which the known solution property is utilized in inferring to the unknown property of a different solution. In the chemistry of acids and bases, titration is used in determining the value of pH for different solutions (Verma, D. 2006). Whenever we carry out an acid-base titration, an indicator is normally used in telling whether the solution is an acid or a base. In other cases an indicator may change its clear a process that is described as a titration end point. In many cases, color changes may be observed in mixing two solutions together in the proportions that are exact. Such a mixture may be defined as an equivalence point. In order to gain more understanding on titrations, an experiment was set to investigate the pH values for different solutions. Hypothesis The hypothesis of the study was to determine the pH at the equivalence point and the unknown concentration of the acids Aim The aim of the study was to find out the pH at different points of the unknown acids concentration. Methodology. Apparatus. The instruments and the apparatus used in this study include Bulb Pipette, burette, conical flask, 3 substances; HCl, NaOH, and CH3COOH, beaker, electrode, Magnetic, stirrer, and the pH meter. Procedure The burette was filled with 1,0 mol of sodium hydroxide dm-3 up to a zero mark. The conical flask was also filled. About 25cm3 of 0.1 moldm-3 of HCl was added using a pipette. The flask was placed on a magnetic stirrer, and the stirrer dropped back into the flask. The stirrer was turned on in the medium to avoid movements of the bar to hit the glass. The titration was them started with a similar volume to that in the table. After each titration the pH for each solution was recorded. The process was repeated for vinegar and hydrochloric acid. The collected data was presented in table 1 and 2 in the results section. Table 1: pH values for HCl V of NaOH PH of HCl 0 1,86 1 1,91 2 1,98 2.5 2,03 3 2,09 3.5 2,22 4 2,43 4.2 2,53 4.4 2,74 4.5 2,96 4.6 3,29 4.7 5,10 5 10,85 5.5 11,44 6 11,64 7 11,46 CV=CV NaOH Acid HCl 4,7x0,514=25xC C of HCl=0,0966 Table 2: pH values of CH3COOH V of NaOH PH of CH3COOH 0 2,91 1 3,76 2 4,36 2.5 4,58 3 4,84 3.5 5,10 4 5,70 4.2 6,38 4.4 10,15 4.5 10,60 4.6 10,75 4.7 10,90 5 11,10 5.5 11,43 6 11,61 7 11,81 NaOH CH3COOH 4,3x0,514 = 25xC C of CH3COOH=0,0884 Graph 1: A graph of base versus strong acid Graph 2: A graph of a weak acid and a base. Discussion In this experiment the set up was used in calculating the quantity of the acid that is unknown inside the receiving flask through measuring the quantity of the tyrant or the base taken for the acid to be neutralized. In many cases, there are two categories of methods used to identify a neutralized solution. The first method involves using a pH meter inside the receiving flask and adding the base up to when the value of the pH reads 7. Another method uses an indicator (Matar, S. 2001). In this case, an indicator is a base or an acid having a conjugate base or acid with a color different from that of a compound that is original. There would be some changes in the color when the solution has a one to one ratio of the mixture of the different forms of colored indicators. From the equation of the Henderson-Hasselbatch, the pH of the solution would be equated to the pH of the indicator when the indicators’ end point is realized. At this point, the solution’s pH and the titrand’s volume would be identified, and the amount of base needed for neutralization of the solution that is not known can easily be deduced. The obtained data was ploted to establish the titrant curves which acted as a profile for the unknown sample. From the graph it is evidenced that the reaction involved a strong acid and base. The graph displayed a sharp region of transition next to the point of equivalence. Equivalent points for strong base, and strong acid curves of titration is always seven since the produced salt fails to go through a reaction of hydrolysis. However, whenever a strong base is utilized in the titration of a weak acid, the equivalence point pH may not be seen as a result of a lagging in arriving at the equivalence point, when a portion of a weak acid is changed to its base conjugate. The second graph displayed a pair of a weak acid and the base conjugate as a buffer. The graph displayed the resultant lag, which preceded the point of equivalence referred to as the region of buffering. In this region, a large amount of NaOH would be used in producing a minimum change in the pH of the solution. Since the base conjugate is basic, the pH would be higher than seven at an equivalent point (Harris, D. 2007). The base titration of the base with the acid gives out a flipped version of a curve titration of the base with an acid. The addition of the acid decreased the pH of the solution. Conclusion In the experiment, all the objectives that were set for the experiment were achieved. The experimental values were different from the theoretical values as a result of errors during the experiment. Some of the errors were as a result of parallax, air resistance, faultiness in calculations, and faultiness in preparation of the solution for the study. References Harris, D., 2007. Quantitative Chemistry. New York : W. H. Freeman and Company. p. 12. Matar, S., 2001. Chemistry of Petrochemic Proces.London Gulf Professional Publishing. Verma, D., 2006. Comprehensive Chemistry. New Dehl: Laxm Publications. Read More