#7 Noteboom Asa Preeti Bhattacharjee, Lab Report

.pdf

School

University of Oregon *

*We aren’t endorsed by this school

Course

227

Subject

Chemistry

Date

Feb 20, 2024

Type

pdf

Pages

Uploaded by CaptainLightning13433

Asa Noteboom, Dylan Minnich Preeti Bhattacharjee 21059 3/12/2023 Determining the Heat Exchanged in Chemical Reactions Safety and Waste Disposal plan (short paragraph): In the lab in order to stay safe we wore goggles as always and this time when we weren’t using the computer we wore gloves in order to protect our hands from the reagents. We also used mixing cups and other devices in order to minimize possible contacts. Waste was all collected in a singular waste container that we acquired and then taken to a class disposal bin where it was later treated and properly disposed of. Materials and methods: We started the lab by setting up the cup and the thermometer correctly and starting logger pro on the computer. For part 1 we added a 100 mL of water, measured out 5.6-5.8 g of Mg(OH)2, started the magnetic mixer and started to mix the water and Mg(OH)2 to create a slurry. Record the initial temp and final temp of the solution, final temperature is determined to be when the line on logger pro stops increasing and flat lines, this is true for all parts. Part 2, restart Logger pro and mass out 7-9 g of citric acid. Add the massed acid into the mixture slowly so that the dust doesn’t fly everywhere and then observe the change in temperature, make sure to record the initial and final temp. Part 3, make sure to clean and empty out the cup of the previous two parts solutions and then add 100 mL of new water. Then mass out the same amount of citric, start logger pro and mix the acid with the water. Observe the change in temperature and record initial and final temp. Part 4 mass out same amount of Mg(OH)2 as part 1 and add it to solution and record the initial and final temp of solution. With all collected data now perform calculations of qrxn, ΔHrxn, and ΔHtotal. Data, Observations, Equations, and calculations: In the lab we used Mg(OH)2 which is a white chalky looking substance and when mixed in water it creates a white milk appearing liquid with the viscosity of water. When you add citric acid nothing changes to the solution visibly. Citric acid is white salt looking substance and when mixed in water it completely dissolves into the solution. When you add Mg(OH)2 to the citric acid (aq) it then turns into the white milky solution just as the first reaction did. Table 1: Recorded Mass of Chemical Reaction and Calculated Values Reaction # Mass base added (g) Mass acid added (g) Volume acid solution (mL) Volume water added (mL) Initial temp (°C) Final Temp( °C) Delta T (°C) qrxn (J) ΔHrxn (J/mol) ΔHtotal (J/mol) 1 5.707 100. 21.0 20.9 -.1 40.7 416.2 206902. 1 2 5.707 7.9787 100. 20.7 30.4 9.7 -3950.7 -208150.7

3 8.0577 100. 21.1 18.7 -2.4 925.7 24116.1 -208784 4 5.6812 100. 100. 18.7 30.8 12.1 -4927 -257016.2 Calculations Part 1: MgOH 2 (s) = Mg(OH) 2 (slurry) Part 2: 2H 3 C 6 H 5 O 7 (s) + 3Mg(OH) 2 (slurry) = Mg 3 (C 6 H 5 O 7 ) 2 (aq) + 6 H 2 O(l) Part 3: H 3 C 6 H 5 O 7 (s) = H 3 C 6 H 5 O 7 (aq) Part 4: 2H 3 C 6 H 5 O 7 (aq) + 3Mg(OH) 2 (s) = Mg 3 (C 6 H 5 O 7 ) 2 (aq) + 6 H 2 O(l) Part 1: q reaction =-q solution = -(3.853J/g°C)(-.1°C)(5.7070g+100g) q reaction =-q solution = 40.73 J ΔH = (40.73 J)/((5.7070 g)(1 mol Mg(OH) 2 )/(58.3197 g Mg(OH) 2 )) ΔH = 416.2 J/mol Part 2: q reaction =-q solution = -(3.853J/g°C)(9.7°C)(13.6857g + 100g) q reaction =-q solution = -3950.7 J Limiting Reagent: ((5.7070 g)(1 mol Mg(OH) 2 )/(58.3197 g Mg(OH) 2 )) = .09786/3 X 6 mol H2O = .1957 mol H 2 O ((7.9787 g)(1 mol Citric acid)/(210.14 g citric acid)) = .03796/2 X 6 mol H2O = .1139 mol H 2 O ΔH = (-3950.7 J)/((.03796 mol citric)(1 mol rxn)/(2 mol citric)) ΔH = -208150.7 J/mol Part 3:q reaction =-q solution = -(3.853J/g°C)(-2.4°C)(8.0577g + 100g) q reaction =-q solution = 924.72 J ΔH = (924.72 J)/((8.0577g)(l mol citric)/(210.14g)) ΔH = 24116.1 J/mol Part 4: q reaction =-q solution = -(3.853J/g°C)(12.1°C)(13.7389g + 100g) q reaction =-q solution = -4927.0 J Limiting Reagent ((8.0577g)(l mol citric)/(210.14g citric)) = .03834/2 X 6 mol H2O = .1150 mol H 2 O ((5.6812g)(1 mol Mg(OH) 2 )/(58.3197 g Mg(OH) 2 )) = .09741/3 X 6 mol H2O = .1948 mol H 2 O ΔH = (-4927.0 J)/((.03834 mol citric)(1 mol rxn)/(2 mol citric)) ΔH = -257016.2 Part 1/2 : Δrxn = 3ΔH1 + ΔH2 Δrxn = 3(406.2 J/mol) + (-208150.7 J/mol) Δrxn = -206932.1 J/mol Part 3/4 : Δrxn = 2ΔH3 + ΔH4 Δrxn = 2(24116.1 J/mol) + (-257016.2 J/mol) Δrxn = -208784. J/mol Evidence and Analysis: a) What is the enthalpy of the reaction? Include both individual and class results in your evidence to support the claims you have made. Our two final enthalpies that we found from our two reactions, (part ½ and part ¾) were -206932.1 J/mol and -208784 J/mol respectively. These numbers were fairly average compared to the wide range of

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version