# HE3key - Name (4 points):_ 3. Write balanced thermochemical...

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Name (4 points):______________________________________ CHEM 1211: Principles of Chemistry I Hour Exam III November 12, 2010 1. Napthalene (C 10 H 8 , MM = 128.171 g/mol) is a solid compound often sold as mothballs. A 3.345 g sample of naphthalene was burned in a bomb calorimeter with a total heat capacity of 8.786 kJ/ ° C, and the temperature of the calorimeter rose from 24.56 ° C to 39.87 ° C. a) Write the balanced equation corresponding to the standard heat of combustion of naphthalene. (4 points) C 10 H 8 (s) + 12 O 2 (g) 10 CO 2 (g) + 4 H 2 O( l ) b) Use the data given above to calculate the standard heat of combustion for napthalene in kJ/mol. (4 points) q cal + q naphthalene = 0 (8.786 kJ/°C)(39.87 – 24.56 °C) + q naphthalene = 0 q naphthalene = –134.5 kJ –134.5 kJ × 128.171 g = 5154 kJ/mol 3.345 g 1 mol 2. Calculate Δ H for each of the following reactions: (8 points, 4 points each) a) Fe 2 O 3 (s) + 6HCl(g) 2FeCl 3 (s) + 3H 2 O(g) Δ H f ° (kJ/mol) 822.16 92.30 400.0 241.82 Δ H = 2(–400.0 kJ) + 3(–241.82 kJ) [–822.16 kJ + 6(–92.30 kJ)] Δ H = –149.5 kJ b) 3H 2 (g) + O 3 (g) 3H 2 O(g) Δ H = ? kJ Given: 2H 2 (g) + O 2 (g) 2H 2 O(g) Δ H = 483.6 kJ 3O 2 (g) 2O 3 (g) Δ H = +284.6 kJ 3H 2
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## This note was uploaded on 10/24/2011 for the course ANP 101 taught by Professor Jaques during the Spring '11 term at Queens University.

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