Procedure Part 1. Enthalpy change for MgO plus HCI Set up the "calorimeter" as shown in the following figure: 1) Measure
Posted: Wed Jul 06, 2022 11:03 am
- Procedure Part 1 Enthalpy Change For Mgo Plus Hci Set Up The Calorimeter As Shown In The Following Figure 1 Measure 1 (134.82 KiB) Viewed 15 times
- Procedure Part 1 Enthalpy Change For Mgo Plus Hci Set Up The Calorimeter As Shown In The Following Figure 1 Measure 2 (145.19 KiB) Viewed 15 times
- Procedure Part 1 Enthalpy Change For Mgo Plus Hci Set Up The Calorimeter As Shown In The Following Figure 1 Measure 3 (123.58 KiB) Viewed 15 times
- Procedure Part 1 Enthalpy Change For Mgo Plus Hci Set Up The Calorimeter As Shown In The Following Figure 1 Measure 4 (122.96 KiB) Viewed 15 times
- Procedure Part 1 Enthalpy Change For Mgo Plus Hci Set Up The Calorimeter As Shown In The Following Figure 1 Measure 5 (73.87 KiB) Viewed 15 times
Procedure Part 1. Enthalpy change for MgO plus HCI Set up the "calorimeter" as shown in the following figure: 1) Measure the mass of 100 mL of HCI 1.0 M and place in the Styrofoam cup (place Styrofoam cup on balance and zero it. Add the HCI in the cup outside the balance and measure the mass of solution). 2) Place the Styrofoam cup in the beaker for added stability. 3) Measure about 1 g of MgO exactly. Record this mass in data table. 4) Open Experiment 19 in the folder from Chemistry with Computers. 5) Put the temperature probe into the HCI solution and record the initial temperature of the solution. 6) Click COLLECT. 7) Add the MgO to the HCl solution and stir constantly. 8) Record the maximum temperature reached. Mass of HCl solution Mass of MgO Tinitial Tmax 89.118 1.006 23.5 C 29.1°C Mass of HCl solution Mass of Mg Tinitial Tmax Part 2. Enthalpy change for Mg plus HC1 1) Measure the mass of 100 mL of HCI 1.0 M and place in the Styrofoam cup, 2) Measure about 0.5 g of Mg exactly. Record the mass in data table below. 3) Put the temperature probe into the HCl solution and record the initial temperature of the solution. 4) Click COLLECT. 5) Add the Mg to the HCI solution and stir constantly. 6) Record the maximum temperature reached (until it begins to drop) 2221 19.099 0.59 23.29 C 50.98 C RTS
Calculations 1) Use the following information to find the AH for Reaction 2 (Part 1 of procedure). qsoln heat absorbed by solution qsolnmsoln Csoln ATsoln msoln mass of solution = MHсI + mMgo Csoln CH204.18 J/g °C (an approximation) AT soln Trinal Tinitial - qRxn2 = heat given off by reaction qRxn2 = - soln nMgomMgo / MMMgo AH Rxn2=qRxn2/nMgo a) Calculate the ATsoln for Reaction 2: ATsoln = Tfinal-Tinitial (29.1 °C -23.5°c) = 5.60 C² ATsoln=eO b) Calculate the msoln for Reaction 2: msoln = mHel + m MgO msoln=10gat 89.118+1.006 = = 90.124g c) Calculate the qsoln for Reaction 2: qsoln = msoln x Csoln x Atson = 90.124g X 4.18 X5.60°C = 2109 d) Determine the qRxn2 : 9Rxn²=9soln 9Rxn² =[21091 e) Calculate the nмgo: nMg0 = mHgO/HMmg O =1.0069/40.30449 =10.025 moles f) Determine the AHRxn2: Express this in kJ/mol. AHRXn2 =qRxn2/nHgO = 2109/0.025 184.36 kJ/mol
2) Now you will repeat these calculations to find the AH for Reaction 3 (Part 2 of procedure). **Make sure you use Mg in place of MgO in the calculations. a) Calculate the ATsoin for Reaction 3: ATsoln=final-Tinitial = 50.48°C -23.29 C =127.19°C) b) Calculate the msoln for Reaction 3: mson ImHCl timigo = 19.0999+0.501g =79.69] c) Calculate the qsoin for Reaction 3: q soln = msoln xCsoln XATsoln =79.6g X4.18J/gc X 27.19°C =19046J₂ d) Determine the qRxn3 : qRxn3= -9soln =-9046 J. e) Calculate the nmg: nMg=mMg / MMmg =0.5019/24.305g 10.0206 moles f) Determine the AHRxn3: Express this in kJ/mol. AHRXn3=9Rxn3/nMg = -9046J/1000 = -9.046/0.0206 =1439.1 KJ/mole),
3) Calculate AHrxn for Reaction 1. Start by fill in the your experimental values for AH's to the right of each thermochemical equation below: (Reaction 2) MgO (s) + 2 HCl (aq) (Reaction 3) Mg (s) + 2 HCl(aq) (Reaction 4) H₂(g) + 1/2O₂(g) -8436 MgCl2 (aq) + H₂O(1) AHRxn2 = MgCl2 (aq) + H₂ (g) AHRn3= -439.1 KJ -225.8KJ H₂O (1) Manipulate these equations above to Calculate the AH for Reaction 1 (Use Hess's Law!) (Reaction 1) Mg (s) + 1/2O2(g) MgO (s) AHRxn1 = ? Show all work and manipulations: MgCl₂ (aq) + H₂0 (1) -> H₂O (s) + 2HCl (ag)-AHRxnz 20 Mg(s) + 2HCl(aq) —> Mg(1₂(aq) +1/2₂ (g) Atrxnz Hrxny H₂(g) + 1/₂O₂(g) --> H₂0 (1) Mg(s) + 1/₂O₂(g) →→→ > MgO (³) =AHRXn2 + AHRXnz + A Hrxny = (-8436 +-439.1 +-285.8) % error =1-640.54 KJ 4) Look up the accepted value for the AHf for Reaction 1. Calculate a percent accepted value - experimental value accepted value AHRxn4= 601.6 -(-640.54) -(-640.154); -601.6 * 100 fror. X100 €6.472% Error
5) How would your reported AH for Reaction #1 have changed (explain) if... a) Some of the MgO remained in the weigh boat and never made it into Reaction #2. . b/c: My reported AH value for Reaction #1 would have been decreased b) Some of the Mg remained in the weigh boat and never made it into Reaction # 3. My reported AH value for Reaction #1 would have been b/c: c) You missed the Tmax for the Reaction #2 and recorded a lower temperature instead. My reported AH value for Reaction #1 would have been d) You missed the Tmax for Reaction #3 and recorded a lower temperature instead. My reported AH value for Reaction #1 would have been b/c: b/c: