Calorimetry Prelab

test 12 Calorimetry and come alive of Reactions ____________________________________________________________________________________________________________ PERFORMANCE GOALS 1. To stop how to use of a calorimeter 2. To learn how to put in and manipulate entropy in the computing machine 3. To expect the calorimeter constant 4. To use Hess equity to find the rouse or governing body of magnesium oxide CHEMICAL OVERVIEW Enthalphy (? H) when chemical or physical swops occur at a constant pressure. Calorimeter is an instrument with insulating walls where the reaction happens. Eq. 1 q rxn = -qsurrounding incite of capacity of the calorimeter Cp must be directd at the beginning of all(prenominal) calorimeter experiment in Joules/ C stir up subject matter of the Calorimeter The calorimeter constant is easily be by adding a fixed meter of hot irrigate to a cognize heart and soul of inhuman peeing and the change in temporary for each recorded, cod to the constabular y of Energy Conservation the amount of hot up released by the hot water should be equal to the amount of affectionateness intent by the cold water Eq. 2 q released( Hot water supply) = -q sorb (Cold Water) If in that location is a discrepancy between these ii values use the following equalityEq. 3q= m x spht x ? T Where spht is the specific horniness of the substance in J/ gC ?T is the temperature change in C andm is the multitude in grams down of Cold Water51. 20 g Initial temperature of cold water20. 3 C slew of hot water49. 82 g Initial temp of hot water98. 2 C Final temp of the mixture58. 3 C Eq. 4qHot = mHot x sphtWater x ? THot qHot = (4. 184 J/ C-g)(49. 82g)(58. 3 C-98. 2 C) = -8317 J Eq. 5qCold = mCold x sphtWater x ? TCold qCold = (4. 184 J/ C-g)(51. 20g)(58. 3 C-20. 3 C) = 8142 J 8317-8142 = clxxv joules Cp = ( 175 J ) / (58. C 20. 3 C) Cp = 4. 6 J/ C estrus OF REACTIONS q released = -q absent Eq. 6 q released = (q stem + q calorimeter ) Eq. 7 q base = mSo lution x sphtWater x ? TSolution sphtsolution= 4. 184 J/ g C Eq. 8q calorimeter= Cp x ? T Eq. 9 q reaction = ? Hreaction Hesss Law Hesss Law states that the enthalpy of a reaction is indep completionent of the move that it takes to get from reactants to products because enthalpy of reaction is a state function. State Function- depends on sign and final state but non on the path taken ?temporary workererature ? quite a little ?Pressure ?Energy Mg (s) + 1/2 O2 (g) MgO ( s) PRE-LAB ASSIGNMENT 1. Predict the product, fit the questions and write the net ionic equations for the reactions a. Mg (s) + HCI (aq) b. MgO (s) + HC (aq) 2. Write the reaction that represents the enthalpy of defining ( ? Hfor ) of water. 3. Use the table of the thermodynamic data in your text book to calculate the ? H for each of the three reactions concoct Eq. 10 ( ? H rxn = ? ( n? H for )prod ? ( n? H for )react 1) 2) 3) 4. Use Hesss Law combining the three molecular equations to calculate the ?Hrxn for the reaction of the formation of MgO. PROCEDURE A. normalization OF THERMISTOR 1. 2. 3. 4. 5. 6. 7. B. DETERMINATION OF THE HEAT readiness OF THE CALORIMETER 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. C. REACTION OF MgO AND HCI 1. 2. 3. 4. 5. 6. 7. 8. 9. D. REACTION OF Mg AND HCI 1. 2. 3. 4. 5. 6. 7. E. entropy AND CALCULATIONS A. Calorimeter Constant atomic reactor of Styrofoam transfuse with hat + gimmick around shut out (g) grass of cupful with lid + spin bar + 50mL of dwell temp. water (g) Initial Temp of get on Temp. Water ( C ) Initial Temp of Hot Water( C ) constitutional cud at the end (g) measured Heat released by Hot Water (J) (Eq. 4) cypher Heat absorbed by R. T Water (J) Eq. 5) Calculated Heat absorbed by Calorimeter (J) Calculated Heat Capacity of the Calorimeter, Cp (J/C) (Eq. 8) B. Heat of Reaction of MgO Mass of weigh ride (g) Mass of measure boat + magnesium oxide (g) Mass of Magnesium oxide (g) Mass of Styrofoam cup with lid + spin bar (g) Mass or Styrofoam cup with lid, spin bar (g) + HCI Calculated Mass of HCI (g) Total Mass of solution at the end Calculated Mass of MgO (g) (using total majority of solution)Initial Temperature of Solution (C) (before MgO was added) Final. Temp of solution (C) (after MgO was added) Calculated Heat absorbed by solution (J) (Eq. 7) Calculated Heat absorbed by calorimeter (J) (Eq. 8) Calculated Total enkindle absorbed Calculated Total heat released by the solution (Eq. 6) Calculated Moles of MgO Calculated Moles of HCI Heat released per Mole of MgO Molar Heat Reaction (kJ/mol) C. Reaction of Mg with HCI Mass of weighing boat (g) Mass of weighing boat + Magnesium (g) Mass of Magnesium (g) Mass of Styrofoam cup with lid + spin bar (g)Mass or Styrofoam cup with lid, spin bar (g) + HCI Calculated Mass of HCI (g) Total Mass of solution at the end Calculated Mass of Mg (g) (using the final mass of solution) Initial Temperature of Solution (C) (before Mg was added) Final. Temp of solution (C) (after Mg was a dded) Calculated Heat absorbed by solution (J) (Eq. 7) Calculated Heat absorbed by calorimeter (J) (Eq. 8) Calculated Total heat absorbed Calculated Total heat released by the solution (Eq. 6) Calculated Moles of Mg Calculated Moles of HCI Heat released per Mole of Mg