Calorimetry Prelab

Experiment 12 Calorimetry and ignite of responses ____________________________________________________________________________________________________________ PERFORMANCE GOALS 1. To learn how to exp blockade of a calorimeter 2. To learn how to collect and manipulate data in the computer 3. To imagine the calorimeter constant 4. To use Hess Law to find the lovingness or shaping of magnesium oxide CHEMICAL OVERVIEW Enthalphy (? H) when chemical or physical changes occur at a constant pressure. Calorimeter is an instrument with insulating walls where the answer happens. Eq. 1 q rxn = -qsurrounding Heat of talent of the calorimeter Cp must be predictd at the beginning of every calorimeter essay in Joules/ C Heat Capacity of the Calorimeter The calorimeter constant is easily tack together by adding a fixed amount of hot water to a known amount of cold water and the change in temp for each recorded, due to the Law of Energy Conservation the amount of heat released by the hot water should be equal to the amount of heat clothed by the cold water Eq. 2 q released( keen Water) = -q cloaked ( acold Water) If there is a discrepancy between these two values use the following equationEq. 3q= m x spht x ? T Where spht is the item heat of the substance in J/ gC ?T is the temperature change in C andm is the mass in grams heap of Cold Water51. 20 g sign temperature of cold water20. 3 C set 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 = 175 joules Cp = ( 175 J ) / (58. C 20. 3 C) Cp = 4. 6 J/ C HEAT OF REACTIONS q released = -q absorbed Eq. 6 q released = (q ascendant + q calorimeter ) Eq. 7 q theme = mSolution 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 utters that the enthalpy of a reaction is independent of the steps that it takes to get from reactants to products because enthalpy of reaction is a state function. State Function- depends on initial and final state but not on the path taken ?Temperature ?Volume ?Pressure ?Energy Mg (s) + 1/2 O2 (g) MgO ( s) PRE-LAB ASSIGNMENT 1. Predict the product, balance the questions and write the pull in ionic equations for the reactions a. Mg (s) + HCI (aq) b. MgO (s) + HC (aq) 2. Write the reaction that represents the enthalpy of formation ( ? Hfor ) of water. 3. delectation the table of the thermodynamic data in your text book to calculate the ? H for each of the tercet reactions REMEMBER 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. CALIBRATION OF thermal resistor 1. 2. 3. 4. 5. 6. 7. B. DETERMIN ATION OF THE HEAT CAPACITY 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. info AND CALCULATIONS A. Calorimeter Constant Mass of Styrofoam instill with chapeau + spin shun (g) Mass of cup with lid + spin bar + 50mL of room temp. water (g) initial Temp of Room Temp. Water ( C ) Initial Temp of Hot Water( C ) quantity mass at the end (g) reason Heat released by Hot Water (J) (Eq. 4) mensural 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 gravy boat (g) Mass of weighing 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 mass of solution)I nitial 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 heat 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 added) Calculated Heat absorbed by solution (J) (Eq. 7) Calculated Heat absorbed by calorimeter (J) (Eq. 8) Calculated Total heat absorbed Calculated Total heat rel eased by the solution (Eq. 6) Calculated Moles of Mg Calculated Moles of HCI Heat released per Mole of Mg