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THE REPORT RESULT OF EXPERIMENT HESS LAW

THE REPORT RESULT OF EXPERIMENT HESS LAW. BY MARCIA SRI PURWANTININGSIH. Hess Law. Aim Observe the enthalpy of reaction between NaOH solid and HCl solution with two ways . APPRATUS /CHEMICALS Apparatus: Beaker Glass 250 mL Thermometer Materials: NaOH solid

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THE REPORT RESULT OF EXPERIMENT HESS LAW

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  1. THE REPORT RESULT OF EXPERIMENT HESS LAW BY MARCIA SRI PURWANTININGSIH

  2. Hess Law Aim Observe the enthalpy of reaction between NaOH solid and HCl solution with two ways. APPRATUS /CHEMICALS Apparatus: Beaker Glass 250 mL Thermometer Materials: NaOH solid Hydrochloric acid 1 M NaOH Solution 1 M Hydrochloric acid 0.5 M

  3. Procedures1. Weigh as soon as possible of NaOH and then store in a closed place.2. Do the experiment in accordance with the following columns.

  4. OBSERVATION Experiment 1 NaOH(s) + H2O(l) NaOH(aq) 2 g 50 cm3 Twater = 26 oC T end = 33 oC

  5. Experiment 2 NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)50 cm31M 50 cm3 0,5M 50 cm3 1M 100 cm3 0,5M TNaOH = 27 oCT HCl = 27oCT initial = 27oCT end = 29oC T end = 30oC

  6. Experiment 3 • NaOH(S)+ HCl(aq) NaCl(aq) + H2O(l) • 2 g 100 cm3 0,5M • T HCl = 27 oC • Tend = 38 oC

  7. Calculation Experiment 1 Q = m . c . t = 50 g . 4,2 j.g-1.oC-1 . 7oC = 1442 joule Mole NaOH = 2/ 40 = 0,05 H1 per mole = -28840 j = -28,84 kJ

  8. Experiment 2 Q = m . c . t = 100 g . 4,2 j.g-1.oC-1 . 2oC = 840 joule Mole NaOH = 2/ 40 = 0,05 Mole HCl = 50 ml . 0,5 M = 0,025 H2 per mole = -33600 j = -33,600 kJ

  9. The other experiment Experiment 2 Q = m . c . t = 150 g . 4,2 j.g-1.oC-1 . 3oC = 1890 joule Mole NaOH = 2/ 40 = 0,05 Mole HCl = 50 ml . 0,5 M = 0,05 H2 per mole = -37800 j = -37,8 kJ

  10. Experiment 3 Q = m . c . t = 100 g . 4,2 j.g-1.oC-1 . 9oC = 3780 joule Mole NaOH = 2/ 40 = 0,05 Mole HCl = 100 ml . 0,5 M = 0,0 5 H3 per mole = -75600 j = -75,600 kJ

  11. Answer of the Question 1. Total equation of the reaction thermochemistry I and II (twice experiment) H1 + H2 = -28,84 kJ + (-33,600 kJ) = -62,44 kJ H1 + H2 = -28,84 kJ + (-37,8 kJ) = -66,64 kJ 2. Write the equation of the reaction thermochemistry III H3 = -75,600 kJ 3. Whether the reaction of III equal to the total of reactions I dan II? No, but equal reaction and II less than reaction III

  12. 4. According to Hess law : HI + HII = HIII Whether your data of experiment appropriate with Hess Law? Yes, although equal HI + HII from my experiment less than asses HIII 5. If not, mentioned several factors cause it! Mistake of balance sodium hydroxide solid, because this balance is not stable, mistake of observation, and mistake of measurement.

  13. 6. Make the diagram for the reaction of the experiment! NaOH(S)+ H2O(l) + 1/2HCl (aq) NaOH(aq) + 1/2HCl (aq) NaCl(aq) + H2O(l)

  14. Proses Skill • Observation • Measure ( cylinder , balance) • Use balance • Inteprating • Reading thermometer • Accuraty • Honesty • Responsibility

  15. Standard of Competence :2. Understanding the enthalpy changes in chemical reaction and its calculations • Basic Competence : 2.2. Determining H of reaction based on experiment, Hess law, standard enthalpy change of formation and bond energies data

  16. Indicator • Calculating enthalpy changes of reaction from appropriate experimental results • Calculating enthalpy change of reaction usingStandard enthalpy change of formation data • Calculating enthalpy change of reaction using Cycle diagram and state diagram • Calculating enthalpy change of reaction using Bond energy

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