Chem B https://session.masteringchemistry.com/myct/itemView?assignmentPr CHEM131

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Chem B https://session.masteringchemistry.com/myct/itemView?assignmentPr CHEM1314 Signed in as Raegan Chambers Hel Glos CHEM1314F 15 Assignment 9 Chapter 6 Multiple Choice Question 159 Chapter 6 Multiple Choice Question 19 Part A ents A 12.8 g sample of ethanol (C2HSOH) is burned in a bomb calorimeter with a heat capacity of 5 65 klrc. Using the information below, determine the final temperature of the calorimeter if the initial temperature is 25.0'C. The molar mass of ethanol is 46 07 g/mol caHOH(I) + 3 O2(g) 2 CO2(g) + 3 hd20(g) H-on .1235 kJ. 28 1 C 53.4°C 742°C 857 C 111°C re My Answers Give Up Subm incorrect: Try Again; 4 attempts remaining 16

Explanation / Answer

m = 12.8 g ethanol

C = 5.65 kJ/C

Ti = 25

MW Eth = 46.07 g/mol

Ethanol + 3 O2 --> 2CO2 + 3H2O dHrxn = -1235 kJ/mol

Qrxn = n*dHrxn

n = mass/MW = 12.8/46.07 = 0.2778 mol of ethanol

Qrxn = ndHRxn = 0.2778mol*-1235 kJ/mol = -343.13 kJ

Note that

Qcalorimeter = -Qrxn

Qcalorimeter = -(-343.13 kJ)

Qcalorimeter = 343.1 kJ

Qcalorimeter = C*dT

343.1 kJ = 5.65 kJ/C * (Tf-25)

Tf =  343.1/5.65 + 25 = 85.7ªC

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