Cryoscopic Determination of Molecular Weight Introduction Colligative properties of solutions depend on the concentration of particles in a solution In this lab we will measure the freezing point of pure naphthalene and then proceed to calculate that of naphthalene and an unknown in a mixture We use the data from temperature measurements to calculate the molality of an unknown in a solution After we take the molality and find the molar mass of the unknown Chemical Responsibility Use care in inserting the thermometer through the rubber stopper Acetone is highly flammable do not use flames throughout the lab Wear safety goggles at all times See Lab Notebook for Calculations Discussion of Results For the first part of the lab I observed the temperature at which first crystals appeared to be at 78 8 degrees Celsius I also found the freezing point of pure naphthalene to be 78 9 degrees Celsius After observing the time vs temperature curve for the naphthalene unknown mixture I determined the temperature at which first crystals appeared to be at 70 9 degrees Celsius and the freezing point of the mixture to be at 71 0 degrees Celsius From this data I for a freezing point depression of 7 9 degrees Celsius and consequently got a molality of 1 14 After multiplying the molality by the grams of naphthalene I calculated the molar mass of unknown to be 181 83g mol Conclusion The lab utilized colligative properties such as molality and temperature to calculate molar mass of an unknown substance Data collection for this lab worked to provide freezing points which was vital for the freezing point depression equation Determination of an Equilibrium Constant Lab Introduction In this lab we carried out a reaction to find the amount of NaOH needed to titrate the reaction mixture Next we calculated the concentration of acetic acid in the mixture at equilibrium being sure to subtract out the blank samlpe After we determined the equilibrium constant using the equilibrium concentrations we calculated Chemical Responsibility Discard contents of your waste beaker into the Waste Equilibrium Constant Acid Base bottle Discard the contents of your 250 mL flast into the Waste Equilibrium Constant Acetic Acid Isopropyl Alcohol Isopropyl Alcohol Acetate bottle Isopropyl alcohol is flammable and toxic by ingestion inhalation Glacial acetic acid is corrosive to skin and tissue toxic by ingestion Sulfuric acid is corrosive to skineyes and tissue Sodium hydroxide is corrosive may cause skin burns Discussion of Results In step one of the lab we found the volume of NaOH needed to titrate the blank sample was 34 mL In the second and third parts we found the volume of NaOH needed to titrate the reaction mixture to be 2 4 mL and 18 5 mL respectively We then calculated the concentration of acetic acid in the original uncatalyzed reaction to be 6 8M and the concentration of acetic acid in the mixture that has reached equilibrium to be 3 22M After plugging in values to the RICE chart we found the equilibrium constant kc to be 1 24 Conclusion The lab utilized different compounds to titrate solutions with NaOH I learned how to calculate the equilibrium constant by finding the volume needed to titrate a reaction mixture Inorganic Synthesis Preparation of Sodium Thiosulfate Pentahydrate Introduction In this experiment we prepared sodium thiosulfate pentahydrate The compound is produced by dissolving powdered sulfur in a solution of sodium sulfite We performed the recrystallizaion of sodium thiosulfate pentahydrate Following the crystallization we performed qualitative tests with other substances such as sodium chloride iodine and hydrochloric acid Chemical Responsibility Na2SO3 is a skin irritant Sulfur is a skin irritant Silver Nitrate will stain skin Iodine is toxic an eye irritant and somewhat corrosive to skin Potassium iodide has no major health risks Hcl is toxic corrosive and will burn skin NaCl has no major health risks Sodium thiosulfiate has no major health hazards The product solution may begin to splatter if heated too strongly Wear safety glasses Discard the filter paper with the unreacted sulfur into the waste sulfur beaker Discard all waste into the inorganic synthesis waste bottle Discard the sodiumthiosulfate pentahydrate product and filter paper in the beaker labeled Waste Sodium Thiosulfate See Lab Notebook for Calculations Discussion of Results In the beginning of the crystallization procedure I found the weight of the empty watch glass to be 61 530 g After the crystals were formed the weight of the crystals and watch glass was measured to be 70 336 g making the weight of the crystals 8 806 g Using the masses of sodium sulfite and sulfur I calculated the mass for the theoretical yield of sodium thiosulfate pentahydrate The mass for sodium sulfite was used since it was the limiting reactant making the theoretical yied 28 4 g By dividing the actual and theoretical yields I found a percent yield of 31 01 Next I observed the qualitative tests When crystals were added to AgCl the solution became cloudy and proceeded to become clear with some solid fallig to the bottom of the test tube When crystals were added to iodine and water the solution went from brownish yellow to a clear color When crystal was added to Hcl the solution became cloudy at the bottom and exhibited a pungent odor Conclusions The lab utilized crystallization procedures and applied the characteristics of sodium thiosulfate pentahydrate crystal to different substances using qualitative tests Kinetics of an Iodine Clock Reaction Introduction Chemical kinetics studies the rates at which chemical reactions proceed In this experiment we mixed varying volumes of KI with constant volumes of thiosulfate and persulfate Differing volumes of KCl were added to maintain a total volume of 50 mL We mixed all the compounds adding persulfate last and measured the time it took for the reaction to change to a bluish purple color We then graphed our data in order to decide if the reaction was first order Chemical Responsibility Ammonium persulfate is a strong oxidizer Dispose of all solutions into the bottle labeled WASTE IODINE CLOCK SOLUTIONS See Lab Notebook for Graphs Discussion of Results For the first part of the lab I observed the reaction temperature to be 20 degrees Celsius As for my data I found reaction times to be quite constant with reaction times for each run increasing at a fairly equal amount The reaction time between run 3 and 4 however exhibited a