Heat of Reaction Lab Introduction Using temperature change of a reaction the enthalpy of a reaction can be found using an equation Two enthalpies of two parts of a reaction can be used to determine the enthalpy of the total reaction using Hess s law calculation Chemical Responsibility Discard Hcl and NaOH waste into the WASTE ACID BASE CONTAINER Wear safety glasses at all times Sample Calculation Heat evolved in a reaction Delta H Mass x Spefic Heat x Change in Temperature Delta H 4 184 J C x 150 mL x 13 C Delta H 8158 8 J Delta H per mole of water formed moles L x M moles 075 L x 2 M 15 mol Heat evolved mol delta H per mol water 8158 8 J 15 mol 54 392 J mol 54 392 J mol 1000 54 392 kJ mol Discussion of Results I found the initial temperatures of Hcl and NaOH to be 18 degrees Celsius and the final temperature of solution to be 31 degrees Celsius The change in temperature was therefore 13 degrees Celsius I calculated the heat evolved in reaction to be 8 158 J mol 8 158 kJ mol For the next part of the experiment I measured the weight of magnesium to be 300 g and the moles of Mg to be 0123 mol The initial and final temperatures of solution were 18 and 36 degrees Celsius respectively The change in temperature was therefore 18 degrees Celsius I calculated the heat evolved to be 11 296 J mol 11 296 kJ mol Conclusion I calculated the enthalpy of water formed to be 54 392 kJ mol and the enthalpy per mole of magnesium reacted to be 37 653 kJ mol Using Hess s Law calculation I then found the enthalphy per mole of magnesium reacted to be 16 739 kJ mol The reaction was exothermic as heat was released and generated Recrystallization and Melting Point Determination Introduction An unknown substance is purified by recrystallization from water and is allowed to dry Its melting point is then determined and its identity confirmed by mixed melting point Chemical Responsibility The hot solution that must be filtered must be handled with crucible tongs or several pieces of paper towel Dispose of the filter paper into the beaker labeled used filter paper Dispose of the filter paper in the Buchner funnel in the beaker labled used filter paper Dispose of the liquid in the filter flask down the drain Dispose of the crystals in the WASTE EXPERIMENT 2 CRYSTALS beaker Dispose your plastic boats into the plastic boats beaker Dispose of the capillary tubes into the capillary tubes beaker Sample Calculations Mass recovered 1 078g Mass unknown 1 704g 1 078 1 704 x 100 63 263 Discussion of Results I found that 63 262 of the crystals were recovered and melted at a 103 degrees Celcius At first I thought that my unknown substance was Acetanilide as I mistakened the melting point as the temperature when the substance was completely done melting When I mixed the unknown with Acetanilide the substance melting at 109 degrees celcius However when I mixed my unknown with O Toluic Acid the substance megan melting at 99 degrees celcius Since 99 degrees is closer to the accurate melting point of 100 degrees celcius I concluded that the recrystallized unknown substance is indeed O Toluic Acid Conclusions I concluded that my recrystallized unknown substance is O Toluic Acid The mixed melting point of my unknown with O Toluic was at 99 degrees while the accusrate melting point is 100 degrees Density Determination Lab Introduction The density of some irregularly shaped chunks of rock is determined The density of solution of NaCl in water of some assigned concentration is determined The composition of the solution made up must be within 1 5 of the assigned value Chemical Responsibility Do not throw the rocks into the sinks or wastebaskets a beaker is provided for collecting rocks Never weigh any chemical directly on the balance pan Either use weighing paper or filter paper Sodium chloride can be poured down the drain Sample Calculations Mass Weight of beaker 67 833 g Weight of beaker plus NaCl 88 010 g Weight of beaker plus NaCl plus water 163 625 g NaCl 88 010 g 67 833 g 20 177 g NaCl Solution 163 625 g 67 833 g 95 792 g Actual NaCl 20 177 95 792 X100 21 063 Density Determination Weight empty graduate 47 880 g Weight of graduate plus solution 75 844 g Volume of solution 25 mL Weight of solution 75 844 47 880 27 964 g Density 27 964 g 27 mL 1 12 g mL Discussion of Results For the first part of the lab I found the density of the rock chunks to be 2 45 g mL I found this by dividing the weight of rocks 20 097 g by the volume of rocks 8 2 mL After for the preparation of the solution I got the required mass of NaCl 20g and volume of distilled water 80 mL needed I found that the actual NaCl percentage in the solution was 21 063 Lastly I found the density of my solution to be 1 12 g mL I found this by dividing the weight of the solution by its volume The temperature of the solution was 17 5 degrees celcius I feel that my density might be higher than it is supposed to be as there were some air bubbles in the solution Conclusions The solution contained 21 063 of NaCl which was close to the assign concentration of 20 I calculated the density of the solution to be 1 12 g mL Determination of a Simplest Formula Introduction An important factor of the concept of moles is the determination of the simplest or empirical formula of a compound By taking the known mass of magnesium it will be converted into magnesium oxide through heating in the air When the mass of the initial metal is subtracted from the mass of magnesium oxide after heating the mass of oxygen in the compound will be determined After this is found the molar ratio will be caculated and will give us the simplest formula of the compound Chemical Responsibility The crucible and cover are fragile If magnesium metal is heated too strongly in air it will ignite and produce a very bright glame that damages eyes To avoid such an incident heat the metal slowly with a small flame Avoid spattering of products in the crucible Wear safety googles Dispose of magnesium oxide product in the Waste Magnesium Oxide bottle Sample Calculation Moles of magnesium used 343 g Mg x 1mol Mg 24 31g Mg 014 mol Mg Moles of oxygen absorbed 087 x 1 mol O 16 g O 0054 mol O Ratio of magnesium oxygen 014 mol Mg 0054 mol O 2 593 error 2 593 2 2 x 100 29 65 Discussion of Results In the beginning of the lab I found my weight of magnesium to be 343 g After heating there was 256 g of magnesium oxide making the weight of oxygen absorbed …