Experiment 22 Determining delta G H and S Chemistry 1220 136 October 29st 2013 Raffeal Bennett Purpose The purpose of this experiment was to understand the relationship between delta G H and S and also Ksp Moreover to explore the relationship between delta G and Ksp and how temperature affects the two Procedure Refer to pages 94 96 of General Chemistry 1220 Laboratory Manual by The Ohio State University Department of Chemistry Hayden McNeil Publishing 2013 2014 Sample Calculations See attached sheet Discussion The average Ksp at room temperature 21 3 deg C was found to be 1 47X10 5 with a Delta G of 27241 J mol and at 94 0 deg C was 1 17 X10 4 with a Delta G of 27635 J mol The Delta S was found to be 54 0 J mol K while the Delta H was found to be 7807 J mol The calcium hydroxide Ksp is normally 5 02X10 6 but mine was a bit lower because the room temperature was also different which could have affected the calculations by a little bit This shows that concentrations were under calculated The decreasing concentrations under calculating of Ca2 and OH will decrease the Ksp and increasing them will increase the Ksp The Delta G at room temperature was lower than the Delta G at an elevated temperature Increasing the temperature makes the reactions less spontaneous because solubility decreases Because normally solubility increases with an increase in temperature calcium hydroxide is a bit different since the solubility decreases with an increase in temperature The Delta S and Delta H both are negative values which correlates to lecture because Delta H is negative and favorable but it can still be nonspontaneous because there is greater decrease in entropy than enthalpy Moreover products are favored in the reaction Possible sources of error include accuracy in measurement and also flaws in the filtration and titrations Imperfections in titrations could cause impurities in the solution which could alter the concentrations Also adding too many or too little drops of the titrants could have an impact in concentrations Conclusion In part A of the experiment the solubility of calcium hydroxide was found at room temperature In part B of this experiment the solubility was found at an elevated temperature These results then allowed to solve for Delta H and Delta S The average Ksp at room temperature 21 3 deg C was found to be 1 47X10 5 with a Delta G of 27241 J mol and at 94 0 deg C was 1 17 X10 4 with a Delta G of 27635 J mol The Delta S was found to be 54 0 J mol K while the Delta H was found to be 7807 J mol Because of the nature of calcium hydroxide increasing temperature will decrease solubility Negative values of enthalpy and entropy are expected because positive Delta G implies negative Delta S because the reaction is not spontaneous The negative Delta H is expected because the reaction is entropic driven having a greater decrease in entropy