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Hess's Law

#### Q. Calculate the heat of formation of ethanol given that the heat of combustion of liquid ethanol is -326.7kcalmol^-1 while the enthalpy of formation of carbon dioxide and water are -97 and -68kcalmol^-1 respectively. Please show the workings

Solved • Jan 29, 2020

Hess's Law

#### Q. Using Hess's Law and some or all of the equations (1) - (4) below calculate ΔH° at 25°C for coal gasification:

Solved • Dec 31, 2019

Hess's Law

#### Q. Using Hess's Law and some or all of the equations (1) - (4) below calculate ΔH° at 25°C for the reaction: NO2(g) + N2O(g) → 3 NO(g). 1. N2(s) + NO2(g) → NO(g) + NO2(g) ΔH1 = +138.1 kJ/mol 2. 2 NO(g) + O2(g) → 2 NO2(g) ΔH2 = –113.1 kJ/mol 3. 2 N2O(g) → O2(g) + 2 N2(g) ΔH3 = –163.2 kJ/mol 4. 2 NO(g) → O2(g) + N2(g) ΔH4 = –180.7 kJ/mol

Solved • Dec 27, 2019

Hess's Law

#### Q. Use molar enthalpies for reactions 1, 2 and 4-8 (repeated below) CH4 (g) + H2O (g) → 3H2 (g) + CO (g) (rxn 1) CO (g) + H2O (g) → H2 (g) + CO2 (g) (rxn 2) C5H12 (l) + 8O2 (g) → 5CO2 (g) + 6H2O (l) (rxn 4) CH4 (g) + 2O2 → CO2 (g) + 2H2O (l) (rxn 5) CH4 (g) + 3/2O2 → CO (g) + 2H2O (l) (rxn 6) CO (g) + 1/2 O2 (g) → CO2 (g) (rxn 7) H2O (l) → H2O (g) (rxn 8) To determine ΔH° for reaction 3: 11H2 (g) + 5CO → C5H12 (l) + 5H2O (l) (rxn 3) There are several ways to do this with the reactions provided here, you will not need to use all of the chemical equations. Solve algebraically for now; you will be given the H values in recitation.

Solved • Dec 4, 2019

Hess's Law

#### Q. Use Hess's law to calculate ΔG°rxn using the following information. ClO(g) + O3(g) → Cl(g) + 2O2(g) ΔG°rxn = ? 2O3(g) → 3O2(g) ΔG°rxn = +489.6 kJ Cl(g) + O3(g) → ClO(g) + O2(g) ΔG°rxn = -34.5 kJ a) +524.1 kJ b) -472.4 kJ c) -262.1 kJ d) -524.1 kJ e) +210.3 kJ

Solved • Dec 2, 2019

Hess's Law

#### Q. Given the following information, determine ΔH for 3H2(g) + O3(g) 3H2O(g). 2H2(g) + O2(g) -----> 2H2O(g) ΔH= -483.6 kj/mol 3O2(g) -----> 2O3(g) ΔH= 284.6 kj/mol (a)−199 kJ/mol (b)−1010 kJ/mol (c)−867.7 kJ/mol (d)+768.2 kJ/mol (e)−440.8 kJ/mol

Solved • Dec 1, 2019

Hess's Law

#### Q. Calculate ΔH for the reaction: CO(g) + NO(g) → CO2(g) + ½ N2(g) Given: CO(g) + ½ O2(g) → CO2(g) ΔH = -283.0 kJ N2(g) + O2(g) → 2NO(g) ΔH = 180.6 kJ

Solved • Dec 1, 2019