Dolores RamirezExperiment #10-Thermochemistry I: Heat Capacity & Enthalpy of SolutionDolores RamirezChem 2 Lab 2LoganApril 28, 2013Experiment #10-Thermochemistry I: Heat Capacity &Enthalpy of Solution1. Introduction: The purpose of this lab is to find the specific heats of two metals, to use the Law of Dulong and Petit to evaluate the molar mass of each metal, and to analyze the enthalpy of sodium chloride and ammonium chloride. 2. Experimental:a) Materials:Chemicals: sodium chloride and ammonium chloride (3g each per group).b) Apparatus:Thermometer with 0.1°C divisions; calorimeters; heating assembly (hotplate); copper and unknown metal cylinders.c) Procedure: 1. Get a copper and an unknown cylinder assigned by you T.A. and weigh each cylinder to the milligram.2. Transport the copper cylinder to a 400 mL beaker placed on hot plate. Then add RO water to the top of the cylinder (at least 5cm above).Note: Don’t drop the cylinder in the beakers.3. Heat beaker to boiling and leave it there for 5 minutes at the least.4. Right before removing the metal cylinder, measure the temperature of the boiling water.5. Clean a 50 mL buret (according to Appendix 10) and use the buret to transfer 80.00 mL of water into calorimeter; consisting of a 2 polystyrene cups in a 250 mL beaker with a square cardboard laying on top of the beaker.6. Put a thermometer in and read it every 15 seconds for 1 minute 45 seconds. Measure the temperature right at the 2 minute mark.7. Use test tube tongs to transport the heated metal to the cupNote: Temporarily shake excess water off the metal before adding it.8. After adding the metal, swirl the calorimeter around and make sure themetal is completely underwater.9. A 2 minutes 15 seconds, swirl the calorimeter and write down the thermometer reading every 15 seconds for around 3 to 5 minutes.10. Take out the metal and dry it and the calorimeter entirely. Carry out a second run with the same copper cylinder.Note: Dry the copper before placing it back in the “copper” rack.111. Pour the water down the sink and carry out the same procedure for the unknown metal cylinder (include a second run). When done, dry the cylinder and place it in the proper rack and pour the water down the sink.12. Graph the temperature on the vertical axis and time on horizontal axis when making a graph of the temperature change for the process.Part2: Enthalpy of Solution13. Add 3g of sodium chloride to a dry test tube14. Take 15 mL of water, measure the temperature, and transport it to the tube.15. Mix thoroughly to dissolve the solid and read/record the temperature.Note: repeat step with 3 grams of ammonium chloride. Make sure to pour solutions down the sink when finished.16.17. With the faucet running, pour all the solutions down the sink.18. Rinse the metal cylinders with distilled water; dry them thoroughly, then return them to the right racks. Make sure to also clean the buret, following directions Appendix 10.19. Wash/rinse all glassware and Styrofoam cups with tap water and distilled water, then dry it.Note: save Styrofoam cups and cardboard lids, unless noted by TA.3. Results and Discussion:All results to this experiment are found on page 5-6. Here I recorded the temperature for copper and mass every 15 seconds until water decreased in temperature. As you look at the data it took the water where the copper was placed longer to drop in temperature and for unknown it took a little over 5 minutes less time for the water to drop in temperature than in copper. To find the calculations for heat capacity in both copper and the unknown are located on page3.24. Conclusion:As conclusion this experiment was successful. We were able to successfully find the specific heats of two metals, to use the Law of Dulong and Petit to evaluate the molar mass of each metal, and to analyze the enthalpy of sodium chloride and ammonium chloride.a) Initialed Duplicate Laboratory Notebook Page(s):i. The initialed duplicate laboratory notebook page(s) must be included after your conclusion upon report submission.5. Report Questions:1)mH 20 ∙ CH 20 ∙ ∆ TH 20=−mmetal ∙Cmetal ∙ ∆ TmetalCC u=mH 20 ∙ CH 20 ∙ ∆ TH 20−mmetal ∙ ∆ Tmetal∆ TCu=27.3 ° C-100°C∆ TH 20=27.3° C−22.7° CCcu=(80 g)(4.184 Jg° C)(27.3° C−22.7 °C)−(56.5 g) (27.3 °C−100 °C)Ccu=.375 Jg°C% error=experimental−literatureliterature× 100 %¿0.375−0.3850.385× 100 %=−2.60 %error2)mH 20 ∙ CH 20∙ ∆ TH 20=−mmetal ∙Cmetal ∙ ∆ TmetalCunnknownC=mH 20 ∙CH 20 ∙ ∆TH 20−mmetal ∙ ∆ Tmetal∆ TH 20=25.4° C−21.6 °C∆ Tunknown=25.4 ° C-100°C3CunknownC=(80 g)(4.184 Jg° C)(25.4 °C−21.6 ° C)−(45.5 g) (25.4 ° C−100° C)CunknownC=.3747 Jg°CI believe that are unknown metal C is zinc because are experimental heat capacity was .3747J/g °C and the closest literature to that was 0.39J/g °C which comes from zinc.% error=experimental−literatureliterature× 100 %¿0.3747−0.390.3 9×100 %=−3.92%error3)(specific heat capacity)×(atomic mass)=25Jmol ° C(x)(63.55 gmol)=25Jmol ° Cx=0.393 Jg ° C¿0.375−0.3930.393× 100 %=−4.58 %errorMolar mass of experimental heat capacity of Cu(0.375 J° C)(x)=25Jmol ° Cx=66.67gmol(specific heat capacity)×(65.38gmol)=25Jmol °C(x)(65.38gmol)=25Jmol ° Cx=0.382Jg °C¿0.3747−0.3820.382× 100 %=−1.91%errorMolar mass of experimental heat capacity of unknown(0.3747 J° C)(x)=25Jmol ° Cx=66.72gmolBased on the heat capacities being relative, low percent errors, the heat capacities agree with each other from the Law of Duolong and Petit. Both values are close to25Jmol ° C , which is also true with the Law of Duolong and Petit.44) The dissolution of NaCl in water is endothermic because our temperature decreased when the NaCl was placed in the test tube. This is due to it requiring energy to break the bond into Na+(aq) and Cl-(aq).The dissolution of Nh4Cl in water is endothermic because our temperature greatly decreased when NH4Cl was placed in the test tube with water having a very large drop in temperature after the addition of Nh4Cl in the test tube means NH4Cl has strong lattice