Study Of Solubility Equilibrium Biology Essay

Study Of Solubility Equilibrium Biology EssayThe solvability ingathering constant of potassium henry tartrate in water and it dependence of temperature were investigated in this experiment. The solubility crossing constant was determined at different temperature through acid-base titration against NaOH. A linear represent was obtained by plotting ln Ksp against 1/T and positive correlation between temperatures and solubility product constant was observed. This study concluded that solubility product constant of potassium hydrogen tartrate is helpless only on temperature.IntroductionThe aim of this experiment is to investigate the solubility product constant of potassium hydrogen tartrate in water and it dependence on temperature. Solubility is a great deal defined the amount of substance required in obtaining a saturated base. Therefore, only a small amount of potassium hydrogen tartrate (KHC4H4O6) is needed to produce a saturated resultant as it has limited solubility in wa ter.In the saturated solution, the rate of the dissociation of the solid is the analogous as the rate of the aqueous ions forming the solid compound the solution is known to be at equilibrium.The equilibrium equation for KHC4H4O6 in the solution can be written asThe constant for the equilibrium equation can be expressed as Ksp = K+ HC4H4O6-.This constant is also known as the solubility product constant (Ksp) which has a fixed care for for a given system at constant temperature. Thus, by finding out the immersion of the ions dissolved, the solubility product constant for KHC4H4O6 can be determined.From the equation above, the dissociation of KHC4H4O6 will produce equal amount of potassium ions (K+) and hydrogen tartrate ions (HC4H4O6-). Thus, by obtaining the submergence of single of the ions, the concentration of the other ion can be derived and the solubility product constant can be calculated. As HC4H4O6- behaves like a weak acid, its concentration can be determined by acid-b ase titration using NaOH, a strong base as the titrant, with phenolphthalein as the indicator. As NaOH and HC4H4O6- react with each other in 11 ratio, the amount of NaOH employ in the titration will be equal to the amount of HC4H4O6- present in the solution.While Ksp is fixed at a certain condition, changes in temperature will affect the value of Ksp. According to the vant hoff equation, the value of Ksp is related to the change in Gibbs free energy and can be expressed asFrom the equation, the solubility product constant depends on common chord variables which are the change in enthalpy, the change in siemens and the temperature. The change in entropy and enthalpy with note to temperature were stated to be insignificant due to the similar heat capacities of the product and reactants. This suggests a linear trend between the remaining variable and Ksp 1. Therefore, a graph of natural log of Ksp versus the reciprocal of temperature can be plot which the gradient of the graph can be used to calculate the enthalpy change and the y-intercept for the entropy change. Thus, the relationship between Ksp and temperature can be observed.Experimental ProcedureDried KHC8H4O4 (0.5002 g) was prepared in a 250 mL conical flask with the help of an analytical balance. Deionized water (25.0 mL) was added into the flask and a standard solution of KHC8H4O4 was obtained. The prepared solution was then titrated against an unknown concentration of NaOH to the endpoint, with phenolphthalein as the indicator. The raft of NaOH used was recorded. The entire role was then repeated with different masses KHC8H4O4 (0.5039 g, 0.5033 g). The concentration of the NaOH was calculated from the volume of NaOH used and tabulated in Table 1.A saturated KHC4H4O6 solution was prepared by adding one gram of KHC8H4O4 into a 250 mL conical flask, containing 100.0 mL of deionized water. The flask was swirled for five transactions and put to rest with occasional swirling for another five minutes at room temperature. At the end of ten minutes, the solution was then filtered and the supernatant was collected in a dry 250 mL conical flask. Concurrently, the temperature of the solution in the filter funnel was recorded. Two portions of 25.0 mL of the filtered solution were then pipetted into two separate 250 mL conical flasks. The two solutions were titrated against the 0.7070M NaOH solution to the endpoint, with phenolphthalein as the indicator. The volume of the NaOH used was recorded. The procedure was then repeated for different temperatures.For temperature above room temperature, a gamy water bath was prepared in a one litre beaker on a hotplate stirrer. The saturated KHC4H4O6 solution was prepared in the same way but was placed in a hot water bath with constant stirring, using a stir bar. The solution was put aside with occasional monitoring until a constant temperature was observed. Next, the solution was decanted in small amount into a dry conical flask. The temperature of the solution in the filter funnel was recorded concurrently. Three portions of 25.0 mL of the filtered solution were then pipetted into three separate 250 mL conical flasks.For temperature below room temperature, an ice-water bath was prepared in a one litre beaker. The solution was also prepared in the same way as the previous procedure and was placed into the ice-water bath. The solution was cooled until the solution stabilized at a certain temperature. The solution was then filtered and the temperature of the solution in the filter funnel was recorded. Three portions of 25.0 mL of the filtered solution were then pipetted into three separate 250 mL conical flasks similar to the above room temperature setup.The sixer solutions were then placed aside for it to return to room temperature and then titrated against the standardized NaOH. The solutions were titrated the same way as the titration done at room temperature. The volume of NaOH used was recorded for the different solutio ns were recorded. The average volume of NaOH used for the same temperature was then calculated and tabulated in Table 2.Data Treatment and AnalysisThe calculations of HC4H4O6-, K+ and Ksp at 302.15KNaOH = 7.070 x 10-2 mol L-1Amount of NaOH used = (7.070 x 10-2 mol L-1) (1.2825 x 10-2 L) = 9.067 x 10-4 molAmount of HC4H4O6- = Amount of NaOH used = 9.067 x 10-4 molHC4H4O6- = K+ = 9.067 x 10-4 / (0.0250 L) = 3.63 x 10-2 mol L-1Ksp = K+ HC4H4O6- = (3.63 x 10-2 mol L-1)2 = 1.32 x 10-3The calculated value of K+, HC4H4O6- and Ksp were tabulated into the table belowTable 2 Determination of Ksp of KHC4H4O6 at different temperatureTemperature / K fairish Vol. of NaOH used / LAmount of NaOH used / molHC4H4O6- / mol L-1K+ / mol L-1Kspof KHC4H4O6285.157.4750 x 10-35.327 x 10-42.13 x 10-22.13 x 10-24.54 x 10-4294.151.0075 x 10-27.180 x 10-42.87 x 10-22.87 x 10-28.25 x 10-4302.151.2825 x 10-29.067 x 10-43.63 x 10-23.63 x 10-21.32 x 10-3309.151.6375 x 10-21.158 x 10-34.63 x 10-24.63 x 10-22.14 x 10 -3320.152.2375 x 10-21.582 x 10-36.33 x 10-26.33 x 10-24.00 x 10-3Based on the temperature and Ksp value obtained in Table 1, values of 1/T and ln Ksp were calculated and tabulated in Table 3. A graph was plotted based on the valuesFigure 1 Graph of Ksp versus 1/TFrom Figure 1, the gradient and y-intercept was obtained as shown in Table 4.The enthalpy change and entropy change was calculated based on the vant hoff equationGradient = (/ R) = -5692.06Standard departure of gradient 99.87= (-5692.06 x 8.314) (99.87 x 8.314) = (47.32 0.83) kJ K-1 mol-1Y-intercept = (/ R) = 12.25 0.33Standard deviation of Y-intercept = 0.33= (12.25 x 8.314) (0.33 x 8.314) = (101.85 2.74) J K-1 mol-1The standard misplay of regression was found to be 0.0295.(Number of measurements = 6, Degree of Freedom = 4)Results and DiscussionFrom the data obtained, the calculated values of and were (47.3 0.83) kJ K-1 mol-1 and (101.85 2.74) J K-1 mol-1 respectively. Ksp of KHC4H4O6 was found to be 1.32 x 10 -3 at 302.15K. It was observed that a linear graph was obtained upon plotting ln Ksp against the reciprocal of T. The step-up in temperature was also found to correlate with the increase of Ksp values. The literature Ksp value for KHC4H4O6 is 3.8 x 10-4 at 291.15K. 2 The approximated Ksp value that corresponds to 291.15k based on experimental data was calculated to be 6.755 x 10-4 as shown in the Appendices. elongated Relationship between T and KspBased on figure 1, a linear model was observed between the reciprocal of T and the natural logarithm of Ksp. This was supported by the R-square value of 0.99 which greatly suggests a linear trend from the experimental data plotted. The standard error of regression obtained from the experiment was found to be 0.0295, which indicates a good fit among the experimental values obtained, corresponding to a good precision of the experimental data. Thus from the linear trend, the claim of insignificant changes of enthalpy and entropy due to tempe rature changes was valid. Therefore, the assumption that the value of Ksp is certified only on temperature at which the diarrhea occurs can be established.Comparison of Literature valuesThe estimated Ksp value based on experimental data was 6.755 x 10-4 at 291.15K and was found to be 43.75% higher than the literature value (3.8 x 10-4) 2. The difference could be accounted to the confinement of this experiment. As the experiment was carried out in different temperature, one of the limitations was due to the apparatus used. The volumetric glass pipette used was calibrated at 20 , thus at other temperature, expansion or contraction might occur leading to the inaccurate volume transferred for titration after the filtering process. Another source of error was noted to be the temperature fluctuation during the filtering process. Although the solution were decant in small portions to minimize errors, rapid increase of the temperature for the cold temperature reading was observed. This co rresponds to the increase in the ions concentration dissolved in the solution, thus resulting in a higher value of Ksp. Despite the percentage difference of 43.75%, the difference between both values was in truth small due to the fact that the Ksp of KHC4H4O6 is a very small value. When the uncertainty of the enthalpy change and entropy change was taken into account, the experimental Ksp value was off-key to be between 3.446 x 10-4 and 1.324 x 10-3(Refer to Appendices). The literature value was noted to be within this range, thus the experimental data do agree with the suppositional value of KHC4H4O6.Change of Enthalpy and EntropyThe change of enthalpy from the reaction was found to be (47.3 0.83) kJ K-1 mol-1. The positive enthalpy change means that the dissolution of KHC4H4O6 was an energy-absorbing process where heat was absorbed during the process. This was expected as the dissolution breaks up the stronger ionic bonds within KHC4H4O6 and weaker bonds between the water molecu les and the ions was formed. These resulted in a positive terminate change for enthalpy for the reaction, which is consistent with the positive enthalpy change derived from the experimental data. The change of entropy was found to be (101.85 2.74) J K-1 mol-1. As entropy was often defined as a measure of disorder, the positive entropy can be explained with the increased disorder brought about when the when KHC4H4O6 dissolved into ions.As the value of enthalpy change was much larger than the entropy change, in order to get a larger value of ln K based on the vant hoff equation, higher temperature was required. This approve with high temperature favors endothermic process such as dissolution of KHC4H4O6, thus it can be concluded that temperature have a positive correlation with Ksp. closedownKsp have a linear relationship with temperature for KHC4H4O6. The temperature dependent of enthalpy change and entropy change was found to be insignificant for the dissolution of KHC4H4O6. As d issolution is an endothermic process, temperature has a positive correlation with Ksp, thus higher temperature allow more KHC4H4O6 to dissolve. This concluded that solubility product constant of potassium hydrogen tartrate is dependent only on temperature.